Winter Solstice, frosts, patchwork and clay/glaze making

The Winter Solstice has come and gone and the days are going to start getting longer and the nights shorter, but the coldest part of the winter is probably yet to come.

We had a crackerjack frost a few days ago, Everything so shimmering silver/white. This mornings frost was much more mild, with just a light dusting of white in the open spaces, less so under the bare branches of the cherry trees in the Chekov orchard. The winter is really just starting, so there will probably be a few more frosts yet where that came from.

In the evenings, as there is nothing worth any attention on the idiot box. I have started to repair another pair of jeans. 

These jeans are about 4 or 5 years old and the front of the thigh part has worn through. That is the most usual place for wear for me. They were the cheapest brand of jeans. 

I had already replaced the pockets with some excellent, robust, pale yellow, linen cloth that should outlast the original flimsy thin cotton that wore through in just two years. Initially in the pocket where I carry my car keys, but then the other pocket as well, just after that. Then it was the edge of the pocket where the new linen lining meets the blue denim.

I reinforced that edge with some red Japanese silk, It look great when it was fist done, but it isn’t really up to it, and is already starting to wear through, so will also need to be redone in the future.

This time I added a front panel of indigo dyed cotton that I bought in the markets in Kyoto a few years back.

Every time I go to Japan, I keep my eye out for street or temple markets where I can find lengths of indigo dyed, or other interesting old fabrics. These are usually some old piece of clothing that someone has unpicked. The hems and loose threads along the edges where they were stitched together are often still visible. Much of this old cloth was woven on small looms in bolts that were only 13” or 330 mm wide. The clothes were assembled by stitching these long thin strips together, to get a wider fabric.

It is an interesting phenomena that cloth dyed in indigo does not rot easily, nor is it eaten by bugs. It seems to last for ages. It certainly makes good patches for work wear like shirts and jeans.

This pair will be good for another 5 years if I keep up the maintenance. The pair that I’m currently wearing to work in the pottery are over ten years old now and still going OK. They have patches on the thighs and knees, as well as new pockets.

My woollen jumper was new in 2004, or 2006. I can’t quite remember. It has quite a few patches of repair, where I have darned the holes where moths have eaten through it, or sparks from welding spatter, or possibly damage incurred during stoking the wood kiln have made holes in it. They all get mended in what I think is a complimentary colour to make a colour spill pattern. It’s a work in progress, It’s 16 or more years old and still very warm and wearable. I like to make things last. i never want to throw anything out until it is really worn out. Repair and reuse, before finally recycling.

I just took a selfie of my Sunday morning jeans. I never take selfies. This must be the first time I’ve put one up on this blog. I’m dressed up to receive some very good friends for Sunday lunch, so I’ve got my best pair on. I’ve been working on these jeans for many years now. I still work in them, but this morning they are straight from the wash and are lovely and clean and suitable to welcome our close friends in. I wouldn’t wear them to try and pass through customs in. But my friends know and understand me. They won’t be affronted.

Actually, I think that work like this is verging on Art. If not a work of art, then its certainly involves some aspect of creativity. I don’t just slap on ‘iron-on’ patches from a sewing shop. I mix and match the patterns and colours to suit my mood and proclivity. Well, that’s my story and I’m sticking to it.

Even the arse end has some good work on it. This wear can be attributed to sitting on the wooden saddle-like seat of the ‘Leach’ treadle potters wheel. The slight swivelling/rocking motion of kicking the treadle with one lag seems to cause the butt end to wear out?

This last week we have made new batches of clay bodies to re-stock the clay boxes. I made a batch of the Mittagong halloysite porcelain from the mafia site. 

This weathered stone is pretty well kaolinised, or in this case ‘Halloyositised’. This makes the stone somewhat crumbly and easily crushed, because the mica and felspars are broken down and weathered from igneous stone to clay-like substance, this causes the loss of some of the alkali fluxes. The stone can then becomes slightly clay-like and less stone-like. However, this creates a minor problem, because as the stone becomes more friable and easily crushed. It can’t be put through the jaw crusher, as the increased clay content causes the crusher to clag up and jam. 

There are two options. The first is to calcine the stone in the bisque kiln and then it will become dry and brittle and easily passed through the crushers and ball mill, but this will completely eliminate the plasticity. So I only do this if I intend to make it into a glaze. If I want to make a porcelain body, I need to retain the plasticity, so the way to extract the clay fragment is to soak the sample in water and then stir it up into a liquid slip. This is called ‘blunging’. However, to make it smooth I need to pass it through a fine screen to eliminate all the unweathered stone fragments that are mostly mica, felspar and silica. In this case, I want all these minerals in the finished porcelain body to create the flux to make it melt and become translucent. This problem is solved by then ball milling the grit residue on the screen and then remixing to two together. This is a rather long and tedious job and I used to do this before I got a roller mill.

The best machine for this kind of material is a roller crusher. I actually have one of these, but it was burnt in the fire and I haven’t managed to find the time to rebuild it. It is still sitting on the crusher room floor in pieces waiting for a quiet period when I get bored 🙂  so that I can find the time to repair/rebuild it. Watch this space. Everything gets done eventually.

In the meantime, in the absence of any mechanical assistance. I decided to crush all the material by hand in the large mortar and pestle, before ball milling it all into a fine porcelain clay body. I used to do this when I was at Art School, as a mortar and pestle was the only piece of crushing equipment that I owned at that time. I still hand-crush small samples up to a few hundred grams for initial testing of field samples. It is quicker than cleaning out one of the bigger machines after use. It’s just like all those kitchen gadgets that are supposed to save so much time, but end up taking longer when you factor in the cleaning and drying, and then reassembly time before returning the gadget to the ‘stuff-that-is rarely-used’ cupboard.

Once reduced to a suitable size, it goes into one of the the mills.

After ball milling, I pass the slip through a 100# screen to remove any coarse particles that may have escaped milling. This halloysite porcelain sample has some iron contamination, so appears a little yellowish in the slip form. This slight iron staining helps create a lovely mahogany ‘flashing’ on the surface during wood firing. The Mafia halloysite is quite variable and is prone to severe warping during the early stages of firing when the halloysite tube-like clay crystals break down and re-form as fractured platelet shards. In this unstable state, the pots can warp and/or crack, so I have found it wise to blend it with some of my other porcelain clay or plastic kaolin to help stabilise the body.

In this most recently collected Mittagong halloysite sample, the site had been eroded badly in the recent rains and all the best and whitest, material had been washed away. Simply because it was the most friable and easier to dissolve in water. Because the remaining material was less weathered and darker than I wanted, I blended it with some more reliable local kaolin based porcelain. 

I have been finding the loading and unloading of the porcelain balls into the larger porcelain ball mill jar quite hard on my back as I age. I have had to load the balls in and out in small handfuls. It takes time and requires and lot of bending and effort. So recently, I built myself a couple of new PVC ball mill jars. These a significantly lighter, although the porcelain balls still weigh quite a bit. For these lighter PVC jars, I made a stainless steel mesh inset for the spare lid. I can easily change the lids and simply up-end the jar over a bucket and let the charge all drain out. I partially refill them with fresh water, roll them along the floor to rinse the balls clean then re drain into the bucket.

The jars are then ready for a refill and to be used again. The balls never leave the jar. So much quicker and easier.

These new PVC jars are made from cheap, standard, over-the-counter, plumbing parts. They are larger, but lighter, than the old one, and I made them so that I can fit two of them on the roller at once. So now I’m able to get more done in the same amount of time..

As I have been throwing and turning the porcelain. I have been collecting the turnings, they pile up like so much fettuccini pasta strands in the hopelessly small Shimpo wheel tray that need to be emptied every few minutes. In the old pottery, I took the plastic trays off and had the wheels in enclosures, so that all the turnings just spilt out onto the floor, but it was a big job to clean it all out and wasn’t suited to the sort of work that I now do, that involves using a large number of different, experimental, small batch, sericite and halloysite porcelain bodies.

So I persist with the tiny tray so that I can recycle each different sericite porcelain body separately to maintain its integrity.

I have been collecting and drying the turnings, then calcining them in the bisque kiln and finally ball milling them to a fine powder to make a porcelain glaze from the porcelain body.

The raw, dried turnings

The same turnings after being fired in the bisque kiln. The low temperature oxidised firing turns the calcined porcelain slightly pink.

The powdered glaze material in the ball mill after milling, ready to make porcelain glaze. 80% porcelain body and 20% lime.

A simple glaze recipe, Self reliance all the way along the line. DIY.

Nothing is perfect, nothing is ever finished and nothing lasts.

Success

Success!

Now that the Open Studio Long Weekend is over. I can get back to the issue/problem of the pug mills.

Success! I made two batches of clay for wood firing and processed them through the two refurbished pug mills.

They both worked just as they should. Instead of taking a whole day to pug the clay through the small 75mm pug mill, as we did a month ago.

This time, using the 100 mm vacuum pug mills we were able to get the clay pugged all through twice, to insure even mixing in record time.

I made a batch of 140 kgs of iron stained wood fired stoneware body in the dough mixer that I bought from my long time friend John Edye after he retired.

The clay mixing room is loosely sealed and has a vacuum nozzle positioned over the machine that is in current use. This removes a great percentage of the dust from the building, keeping a slight negative pressure in the mixer room and stopping any dust from migrating into the pugging room.

After the clay is removed from the dough mixer, it is placed on the clay trolley and wheeled out of the mixer room and into the pugging room, where it is pugged twice, blended, bagged and boxed.

I scrape, scrub and then sponge out the dough mixer bowl clean as soon as the clay is removed from the bowl. It is best to do it as soon as possible, while the clay is still moist. 

It makes the job a whole lot easier. I take charge of mixing the new clay body batches in the vacuum sealed clay mixer room while Janine does all the pugging in the next room.

The fresh clay is then pugged through John’s 100mm. Venco pug mill that dates from the mid ’70’s. This pug mill is the first model of this size made by Geoff Hill. 

It is currently disguised as a very large pretend musk stick!

We pug the clay through twice. The first time we stack all the pugs up in a pyramid fashion, then chop all the ends off the clay sausages, working our way back through the batch of clay to minimise any slight variations from batch to batch. Taking clay from the first, middle, and last pugs and blending them back through the machine.

It turns out that Geoff Hill learnt a lot in the building of this first model. And soon made changes to improve it’s design. 

We bought our first 100mm. Venco about 6 months to 1 year later than John and we ended up with the second, re-designed model.

As it turned out the second model worked faster and was quieter than the first model.

I didn’t realise this at the time, but as we now have one of each of these earlier pug mill models running side by side, we can experience the differences.

When I made the second batches of clay. The wood fired porcelain clay body. Janine used the pug mill that we were given from our lovely friend Jane in Melbourne. 

With its new reconditioned motor now in place, it works beautifully – now!

This is a later model pug mill. Possibly built a decade later than John’s pug. It is much quieter, runs a touch slower, but is much faster and is self feeding. 

It runs a little bit slower, but pugs the clay a lot faster.

It doesn’t need a lever plunger to force the clay into the barrel. The clay is just naturally drawn into the pug barrel. This is how we experienced the use of our old original Venco pug mill from 1978.

I attribute this to the design of the blades as they are set up on the shaft. The newer model has the blades a little bit closer together, so that there are no ‘dead’ spots and is a great improvement.

After pugging both batches of clay and storing it all away in the plastic lined clay boxes. Janine puts the chooks to bed and then goes to the house to light the kitchen stove and start dinner.

I wheel the pug mills out of the way, and then wheel the clay bench and pug sausage tables both out of the way. So that I could wet mop the floor and get it scrupulously clean, before wheeling everything back in place. Ready for the next batch.

The mixer room is also mopped clean.

This practice, keeps the clay room spotlessly clean and minimises air born dust diseases.

I’m actually too old to die young now, but I still want to protect everybody else that comes here to visit.

Our on-going pug mill saga

Over the past couple of weeks, we have been making pots, working towards the June Long Weekend ‘Pop-Up’ Open Studio Weekend.

I have finished building work for a while. I need to be making pots, no more work on the house until later in the year. I still need to fireproof the facia and eves of the roof against ember attack. The roof is now completely watertight. That’s the first step complete. Andy came back to help me fit the last sheet of roofing iron and then screw down the ridge capping, while I followed behind peening the ridge capping into the corrugations of the roofing iron. A very solid, proper, solid job of roofing. I’m glad that roof work is now over for some time. 

In the pottery we have been throwing and turning domestic items like cups, bowl and plates to fill out the shelves for our Open Studio Sale. 

I made 100 cups.

On the on-going pug mill front. I stripped down the big blue pug mill and took the motor off and sent it away to be re-wound and repaired – if that is at all possible? I should know in a weeks time. In the mean time, I took the worn-out vacuum pump off the purple pug and swapped it for the good one that was on the blue pug. So now I have a good working 3” purple pug that we are using for our white stoneware clay and the buggered vacuum pump is now on the blue pug mill that has no motor. A matching pair of non-goers. Well for the time being at least. I will get back onto that problem after our Open Studio Sale. 

The blue pug is hoisted up onto a tressle to keep all the new, clean gear box oil down in the gear box while I take off the motor. There is no easy, clean way to drain the oil without some mess, so I’m leaving it here for the time being. Hopefully the motor can be rebuilt and back on the machine within a week or so?

I rang my friend John Edye recently and enquired about the 4” Venco Pug mill that he had for sale a while ago. I bought a lot of his equipment last year when he retired. I didn’t make an offer on the pug mill, as I thought that I was going to get a couple of pug mills from other friends. As these have proved to be a little bit problematic. A rang John and asked if the big pug was still for sale and amazingly it was. I’m so lucky! I bought it over the phone and made the trip up to John’s place to pick it up. Luckily, it isn’t as far away as Melbourne and I could do the return trip all in one day. John assured me that it worked, but that it had a lot of corrosion inside the barrel. I’ve dealt with that before over the years by fill ing the worst holes with a home made epoxy based filler, or ‘wick-in’ thread sealant, that seeps into crevices and sets in the absence of air.

When I got the pug mill home, I was able to lift it off the truck and straight onto a wheeled, steel pug trolley that I had welded up in advance. I even had a vacuum pump cradle welded on underneath for the pump. These machines are way too heavy for me to lift, so having them on a mobile trolley is the way to think about them.

It’s interesting that this machine is the first model of Venco 4” vacuum pug mill and presumably dates from the late 1970’s. It has an inline plunger handle and all the castings are different from the later models.

I had a bit of trouble getting all the bolts loose to strip the pug down to clean it out. A few bolts needed the impact-driver to get loose and one snapped off, requiring the hole to be drilled out and the thread re-tapped. Slow and a little bit tedious, but all do-able.

The pitting is deep, but hasn’t gone through the wall and with a little bit of maintenance, will see me out I’m sure. I cleaned everything back to the metal. There was a lot of flakey white aluminium oxide to clean off.

Some etch primer, followed by a couple of coats of paint and it is all back together now and ready for work. I’m not too sure how John will take the new colour scheme I’ve chosen to cheer up the clay making area of the workshop? Pink, purple and mauve, with a little bit of black detailing. I like it!

When all of this clay making machinery trouble is all sorted out, it will make our life so much easier. I am committed to making almost everything myself. To be as self-reliant as possible, in food, in water, in electricity, in wood fuel, and this extends to clay and glaze making in the pottery. The principal difficulty that I am dealing with here is that I’m trying to replace in a couple of years, what it took me to build up over the past 40 years of life experience. I don’t remember it being so difficult in the past, but I guess that I was only dealing with one or two problems per year over that extended time. Now I’m trying to do everything at once. It is a bit easier this time around as I have more life experience and more skills, but I’m so much older now and I don’t have the same energy that I used to. I certainly find it harder to go back down to the workshop at night, after dinner and continue working. Although I still do sometimes!

Bummer

I thought that everything was going so well.

Well, I thought it was. With 2 pug mills apparently fixed. I decided to make up a few batches of clay in the repaired ‘phoenix’ dough mixer. We had run out of the last quarter tonne batch of clay. All we had in the clay box were several bags of recycled turnings that really needed wedging thoroughly, or pugging. We opted to mix all the re-cycled turnings in with the new batches of clay and pug it all together. All well and good. It should have been so easy.

The dough mixer worked perfectly and I soon had a batch of plastic clay on the clay trolley and out to the rebuilt pug mill. Janine started pugging the clay while I mixed a second batch. Each batch is comprised of 100kgs of dry powdered clay, felspar and silica. These powders are all mixed together dry,  then I add 24.5 kgs of water to the batch and the mixer stirs it all together into a stiff plastic, sticky mass. It then has to be hauled out of the mixing bowl,  bit by bit and stacked onto the clay trolley to be wheeled out to the pug mill.

I could hear the big pug motor ‘whirring’, the gear box grinding, and the vacuum pump making its ‘phut’, ‘phut’, ‘phut’, noise. as I worked in the clay mixer room. Then nothing. When I came out to get the clay trolley to reload it with the 2nd batch. Janine was standing there looking a bit puzzled. The pug mill had stopped. The motor was working when I rebuilt it, but that was without any load on the motor, just ‘free-wheeling’ . As soon as the clay went in, the load on the motor increased and it just stopped. The over load switch clicked in and it wouldn’t restart.

Bummer! We now had 2 loads of clay needing pugging and a machine full of clay, but no action. I couldn’t do anything about it right there and then. The machine will need to be stripped down again at some stage. But right now I need to pug this clay. The only option was to wheel ‘Pugsly’ out. I was hoping to keep it clean and ready to pug the first batch of porcelain clay. That’s now a pipe dream. We start pugging the white stoneware through Pugsly. It starts well enough, but then I realise that the vacuum pump isn’t working. It’s making the right noises, but the clay is coming through with air bubbles in it. I can lift the lid off the vacuum chamber white it is working. This lid should be severely locked down tight by the vacuum pressure. Again, I can’t do anything about it immediately, I’ll have to figure it out later. I need to get the clay made, bagged and into the clay box, before it dries out.

I just spent a month of all my spare time re-building these two machines. One doesn’t work at all and the other doesn’t work a very well. I’m a complete failure as a mechanic. This is a real lesson in humility. When all the clay is finally pugged. Tonights dinner will be humble pie for me.  One small up-lifting part of this whole disappointing exercise is that the paint work was a success. It’s bright, colourful and cheering. That’s a small reward.

We spend two days processing all 400 kgs of clay and putting through the pug mill twice. Each batch is pugged and laid out on the clay table in rows and layers of sausages. Because there is the possibility that I could have made an error while weighing out the dry ingredients, or that there might be slight variations in the materials as delivered in the various bags. We pug all 4 batches of clay, then chop the ends off every sausage and re-pug the clay to make sure that every sausage that come s out of the 2nd process has all the same consistency. This is then bagged and stored in the clay box. It’s a bit of teamwork to get it all done efficiently and as quickly as possible, with as little mess as possible. However, inevitably, There will be some clay that gets dropped on the floor.

Once all 400 kgs of the clay is pugged, bagged and in the clay box, a very slow process, as the 3” pug is so much slower than the bigger 4” one. We have to clean up the floor to control the dust. A very small successful part of this protracted failure is that I built all the clay tables and trolleys on wheels, plus I mounted both pug mills on castors. We mop the floor all around the pug mills. Then wheel everything out of the way, and clean the floor under where the pugs were. It’s all quick and easy, and every part of the process of cleaning up is a success. It’s soon time to roll everything back into place. Ready to start pulling both machines to bits and finding out the problems involved, then sorting it all out.

Jane’s big pug has a motor problem. It wants to start, but can’t get going. It must be the starter windings or the starter capacitor. I pull the motor off and take it into town to find someone who knows about such things, to get the parts that I need to get it going again – hopefully. I’m told that it is most likely the starter solenoid. There isn’t one to be had in Mittagong at either of the electrical workshops, so I order one. It should be in next week. Watch this space.

Now for Pugsly’s vacuum pump. I think that it is something to do with the valve, hose and filter, vacuum air line. I disconnect the plastic hose, turn on the vacuum pump and put my finger over the end of the hose and it has hardly any suction at all, but there was some, just a tiny bit. I pulled it all to bits and found a few things out. The first was that the filter had been installed back to front at some stage in the past. Someone has had it to bits at some stage in the past and put it back together back to front. I hadn’t thought to check that when I started work on it. I’m totally hopeless as a fitter and mechanic.

When I got it off. I also discovered that it was chocker block full of white clay – on the pump side, not the pug side of the line. This is theoretically impossible, so that was a bit distressing. As I continued to dis-assemble it all, I also found that the sump of the pump had white clay mixed in with the oil! That would have ground out the bearings! I drain the oil out and replaced it with fresh oil. Ran it for a short time to rinse out all the old oil from the crevices, then drained it again and refilled it with new oil again. After reassembly, I test it and it has quite good suction. So not such a bad outcome. 

I decide to have a look at the vacuum pump on the big pugmill. I discover that it has been over filled to the brim with oil. I drain 2/3s of it out until it is back down to the indicated upper level in the sight gauge. Everything else seems to be in order. However, because I’m such a hopeless mechanic, there could still be more issues to deal with the next time that we get to test these machines out.  

It would have been so much easier to buy new machines from the start and I wanted to. I even had the money for them set aside to pay for them. But ‘Venco’, the pug mill manufacture here in Australia closed down a few years ago, when Geoff Hill, the proprietor died. The company has re-started under the new ownership of his grand son, but only in a very small and intermittent way. They have no plans to produce the 4” pug mills for some time yet. So far they have only made 2” pug mills, with the first batch of 3” pugs coming through now.

So I am stuck with my ineptitude to muddle things through.  I will get it all done, but it is frustrating and very, very slow.

A BIG Day

We are potters again!

We have our hands in clay again – finally. It’s been 19 months and 3 days since the fire.
Today we made our first batch of clay in the new pottery clay making room in the new shed.
I spent part of Friday fabricating a wedging bench, because there would be nowhere to work the new batch of clay coming out of the dough mixer into balls and then blocks, before bagging them up, and moving them to the new clay boxes. So I needed a strong bench.
Every step has been considered and planned, so I have already built the plastic lined clay boxes. Installed the dust extractor. Rebuilt the dough mixer – for the 2nd time after it was burnt in the pottery fire in 1983 and then again in 2019. Making the wedging/clay prep bench was the last step.


I incorporated a marine ply splash back on my bench, so that in the future, I can stack clay on to the bench quite high prior to pugging, without it falling – that is, once we manage to get a pug mill. We have had one gifted to us, but as we are all in lock down. I can’t get it.We are making clay anyway and bagging it up to age in the new clay box, so that when we get a pug mill, we will vacuum pug it and can use it straight away.



All the dry powdered ingredients are accurately weighed out on the scales and placed slowly and carefully into the dough mixer bowl to minimise any flurry of dust rising up out of the bowl. Any dust that does rise disappears up into the bright orange tube of the exhaust fan mechanism and is issued outside.We mixed the powders dry for a few minutes, until all the ingredients were the same colour and all sense of difference was mixed and mingled in together. Then I added the exact, measured amount of water and let it continue to mix for several more minutes, until the batch becomes stiff and starts to ‘ball-up’. 
I’ve learnt that this is the time to add the remaining small amount of water that was withheld from the first pour. This last issue of extra water wets the stiffer ‘balled-up’ ingredients and softens them, I then Iet the mixer run for several more minutes until everything is smooth and plastic.
Amazingly, when I rebuilt the mixer this time around I had to reshape the mixing bowl that had gone out of shape during the fire and had 4 large splits in the metal rim.The bowl had been a little bit pear shaped since the first fire in ’83. So much so that the mixing arm used to bang into the side of the mis-shapen bowl and had scraped all the paint off in one place. Now after this last fire and re-working, I had to clamp it into some sort of semblance of a round shape as I panel beat it back into a useful shape. I had no real idea of how to approach a job like this. I’m not trained in metal work, just entirely self taught. I muddle through most difficult jobs, lurching from crisis to crisis. I manage to succeed by shear graft and persistence, rather than knowledge and skill. So, I was totally amazed that when I came to use the dough mixer this time round,  I discovered that I had indeed managed to make it almost perfectly round again. Well, not perfectly round, it still has a distinct wobble in it, but there is no impact on the wobbly side anymore. There is no wobbly side! Just a general overall wobble. Sort of evenly wobbly! I managed against all the odds to repair it really well. I fully expected it to be worse, not better. I’m no panel beater. So I am really amazed! it’s such a fluke! I am very pleased.



As the clay absorbs the water, it stiffens and balls up.



The hardest part of this ‘dry-mix’ clay making, is having to dig the stiff and sticky plastic clay out of the mixer bowl by hand. In the past, I would unload the clay from each batch into a bathtub next to the mixer. I used to make 8 batches in a row, one after the other, and that would make up a tonne of clay. Enough to fill one clay box. Then I would pug it all through the pug mill with no vacuum to speed up the process (the vacuum process slows down the speed of through put). I stacked all the first pugs of clay in a large pyramid stack and then re-pugged it all again with the vacuum on. This time slicing off all the ends of the previous pug sausages and mixing them all together in one handful into the pug mill hopper. This ensured that any mistakes or slight variations in the 8 different mixes were all averaged out in the final pug sausages.
It used to take me all day to make up, twice pug, then bag and box a tonne of clay. It was a long day and quite hard work overall. I stopped making dry mix clay over a decade ago. For the past ten years or so, I was crushing, grinding, and ball milling all my porcelain stones, to make my porcelain stone ‘clay’. The only time that I used the dough mixer in the past few years, was to make a big batch of wadding for the wood fired kiln.
However, now, on this occasion, we have no pug mill, so it’s all to be done by hand, we work it up by hand into round balls of a couple of kilos, pounding 3 of these together into a block and stacking 3 blocks one on top of the other, before bagging the lot.Each batch we make is 130 kilos and we make 2 batches. It has taken us about an hour and a half for the first batch, but we get better at it, and the second batch only takes one hour to weight out all the ingredients, mix them and unload the batch and bag it all up and place it into the clay box.
I scrape down the mixing bowl between each batch, because I don’t want the thin remnants of clay drying out and going hard between batches and causing lumps later, that will need to be hand wedged to be sorted out.



After we have finished the 2nd batch, I sponge down the mixer and clean the bowl, ready for the next use.



As I made the mix a little wet, to allow the water to fully integrate into the clay as it ages. We left the last 25 kgs out over night to stiffen up a little, so that we can wedge it up tomorrow, wire cutting it and kneading it to remove the air bubbles and get this small amount ready for the wheel. I will need to make a series of clay test to get to know this clay, but also to provide tiles for glaze testing. We aren’t ready for any throwing yet.



We haven’t moved the potters wheels that we have been given and loaned by our friends out of the storage barn yet. There is no room to install them in the studio just now, as it is full of stuff that I am still working on, but the time is getting closer. I still need to finish welding up the benches and table for the centre work station of the studio and a table for the gallery. That will be my next job. Meanwhile, the clay is resting in the clay box and hopefully ageing and improving a little

Ventilation

There are now lots of small jobs to convert our cheap and nasty metal framed farm shed into a functional pottery studio. I had to fill the little gap above the wooden windows, between the metal lintel bar that supports the arch brickwork. This is to stop sparks and vermin getting into the cavity. It also looks better and more ‘finished’, but really, I just had to get it done to complete the building so as to get our final approval and occupancy certificate. 

The next most pressing job was to install OH&S ventilation. A fan in the materials processing rooms to take the dust away from the rock crushers and clay mixers. I never had to worry about forced air ventilation in the past, as the machines were more or less outside in the breezeway between the two pottery buildings. Now that I have them all in the one sealed room. It is essential that I fabricate and install good ventilation.


This metal tube has some 2nd hand/re-cycled 1.5mm stainless steel mesh inserted to stop sparks and insects getting into the building.


And a cheap batroom fan in the other end that will be inside the room.

Connected to a long flexible air hose.


With the exhaust fan embedded in the wall, I can direct the cheap flexible suction vent hose to any machine in the room.

I have no idea how other people might achieve this sort of dust extraction, but this is one cheap alternative solution, and mostly home made.

Clay? What OH&S risk?

Final Inspection and Prepping for Clay Making

We have been working a bit frantically to get all the things on the list completed so that we can get our final inspection, which, if our building passes, will entitle us to get our occupancy certificate. Once we have this, we can legally move in and fill the place up with pottery equipment and start to use the space as it was intended.
The Council Building Inspector called in today in the late afternoon. He gave our work a good scrute and declared that we had completed everything on the list to his satisfaction. He issued us with a carbon copy of his Final Inspection Report and was very complementary about the way that we had transformed a cheap, kit form, tin shed(s) into an interesting building. He commented on our sandstock brickwork and the arch window that visually links the new pottery shed to the Old School building and our use of recycled, old gal iron to enhance the visual amenity of this historic site. I was chuffed.
We celebrate with a dozen oysters off the fresh fish truck that come up from the coast on Wednesday, Thursday and Friday, paired with a couple of cheap sushi trays.


Now we can legally move in. Actually, he didn’t comment on the fact that we already had moved in our kilns, clay mixers, rock crushers and ball mills, the benches, pan break and guillotine, they are all in there and ready for work. I have been using the maintenance shed for a couple of months now to restore my machines and actually make the components to fit out the rest of the building.

One of the first things on my list now, is to make some clay, so that it can ‘age’ for a while, to improve its plasticity, so that when we start to make pots again, the clay will be more workable and respond better on the potters wheel. Having a bit of time to age is very important for freshly made clay, when it is made from powdered materials.

Ageing isn’t so important when clay is made by the wet method involving a slow stiffening back from a liquid mix where the raw material is in the crude natural form straight from the ground.


It might be worth explaining here a little bit about clay. When clay is in its natural crude form, it has a multitude of fine, flat, hexagonal particles, sort of laminated like pages of a book. When the clay is soaked in water and stirred into a watery ‘slip’ or slurry, these flat sheet like crystals are slowly liberated one by one and flake off from the ‘book’. This process takes time. The finer the particles, the more ‘plastic’ and workable the clay can be, realising the best of its potential, but it also takes a long time to get the water in between the various surfaces. 


Stirring the clay and water mix or ’slip’ up into a fine slurry, sieving it to remove any unwanted particles and then letting the slip sit and settle takes time. Sometimes, the clay particles in the slip don’t settle out due to gravity allowing the water to come to the top where it can be decanted off. If the slip doesn’t settle out, then the mixture has to be tested, measured and treated. This involves measuring the pH of the slip. Usually, the clay will need a small addition of an acid to change the pH to very slightly acid.

 
Clay particles have an electrostatic charge on their surface. Clay chemistry is very complex, but suffice to say briefly here that clay particles are a little bit like small magnets. What is needed is to get the positive and negative charges to balance so that they attract each other and not to repel. If they are repelling each other the clay will never settle, but stay suspended and cloudy forever. Once acid treated they can be made to become attractive and will form larger clumps that are affected by gravity, and so settle to the bottom, allowing the water to be forced up where it can be decanted off. This process is called ‘flocculating’ . Think of a mob of sheep forming a flock.


I’ve tried many different ways of flocculating my clay particles. Old red wine that was undrinkable due to cork taint, there isn’t much red wine that I wont drink, but cork taint is one that isn’t drinkable, then I’ve tried cheap commercial vinegar, even cheaper imitation vinegar, dilute brick cleaning acid from the hardware, or epsom salts, but my ‘go-to’ dilute acid is the water in our old pottery water tank full of rain water ( carbonic acid) that has been affected by the constant fall of gum tree leaves onto the old pottery iron roof. This caused the roof to rust and created a moderately acidic solution of carbonic and tannic acid. It came out of the tank pale brown, like cold black tea. When I used this water to make slip I didn’t need to add extra acid. I much prefer this natural method of flocculation. It suits my life philosophy of living naturally as possible and treading gently combined with minimal consumption. Once the clay has settled to the bottom and the excess water removed, the thick slurry can be placed out side in the sun and wind to stiffen. 


This wet method using crude clay is a very slow process. So to speed thing up potters use can use dried powdered kaolin and powdered non-plastics like felspar and silica blended together in a set recipe in the dry state and then just enough water is added to bring the mix to the required plastic consistency. This is akin to making a cake. Although fast, this method doesn’t wet all the available fine particles and the clay doesn’t develop its full potential plasticity. Its a compromise like everything else in life. This dry mix method is fast and efficient and with a tiny addition of some extra plasticiser like bentonite, the preemptive addition of some acid to the water and a period of ageing, then a reasonable result can be obtained. That is what I intend to attempt this coming week. 


When life settles down a little and we have more time, I will make the next batch of clay body by the wet method, using my larger ball mill to mix the liquid slip and allow the slip to sit as a liquid in a large plastic drum for some time and then slowly dry the slip out. This is designed to realise the maximum potential plasticity of the clay body, and is what I have been doing for the past decade to get the most out of my porcelain stones. As they are not inherently plastic, they need all the help that they can get. Tragically, In the fire I lost several tonnes of milled porcelain stone body that I had been ageing for up to 10 years for use in my dotage. 


Before I can make this first batch of quick and dirty clay, I want to make a clay storage box to keep it in. Clay ages best somewhere cool, dark and where it will keep damp with a minimal amount of condensation, that means no direct sunlight, so a plastic lined, heavy duty wooden box has worked well for us for the past 35 years. 


Luckily, back in 1983 when we were building our last pottery shed, after our 2nd fire, I saw two packing cases on the side of the road placed there outside a factory for the taking. 1200mm x 1200mm x 900mm. Big enough to hold a tonne each. We would fill them and when we had used up the first tonne of clay, we would make another tonne to replace it, and then use the other box full while the freshly made tonne was left to age and improve. We kept up this swap and go method of ageing our clays for many years.
Unless I can find two more suitably sized packing cases on my way to the timber-yard today, I’ll be buying a couple of sheets of ply wood and a big sheet of heavy duty plastic, to make some new clay storage boxes.


I still need to line them with plastic – maybe tomorrow?

Our Old Twice Burnt Dough Mixer Proves to be a ‘Pheonix’ mixer

Janine and I bought a very old and well used bakery dough mixer back in 1978. This was a time when a lot of old, small, family run bakeries were being forced out of business by the big multinational food corporations, and a trend towards people buying mass produced bread in super markets, rather than going to the small family bakery.We didn’t have 3 phase power back in those days, so I adapted the dough mixer to run on the power from a 5HP petrol engine interfaced through a rather snazzy torque converter. The sort of thing that adapts automatic gear boxes to engines in cars. I was given it, so didn’t realise how expensive they were.
We used that dough mixer in conjunction with a 200 mm. Venco de-airing pug mill for 5 years to mix all our clay bodies. Tragically, That pottery burnt down in 1983. That was a timber building and was totally destroyed by the fire. What was really amazing, was that I was able to rebuild both the pug mill and the dough mixer from the melted and charred remains. I spent a lot of time working on that equipment to get it going again. Luckily this machine was housed in a corner of the building with 2 sets of glass double doors on the corner, so as to allow for good ventilation. As this part of the building had very little wood in it,  the machine didn’t get too hot during the fire and none of the cast iron parts cracked.
The shaft of the dough mixer got rather bent during the fire, so had a very noticeable wobble in it when I got it going again, but at least I got it going. It was a bit of a mess, but I managed to keep it going for the next 36 years. After that fire, I converted it to a 3 hp single phase electric motor. The biggest motor that you can plug into a 15 amp power point, as that was all the power that we had at the time. It only just managed to do the job, as it wasn’t really powerfull enough, but I was carefull with it and nursed it along. I set it up with a home made, somewhat loose, slip-belt clutch as torque converters are so expensive.

After this last fire in 2019, The machine really got cooked, That’s it in the centre of the picture above, in the burnt out shed. Fortunately, the fire didn’t crack the castings. However, this time the main shaft was so badly bent, that it wouldn’t even rotate. I gave up on it, as I had so much to do to rebuild the new pottery shed that I couldn’t see myself ever really finding the time to fix it. Then, when my friend John Edye retired. I was able to buy his dough mixer. Very lucky timing. I didn’t have a pottery to put it in at the time, but bought it anyway, to make sure that I had it ready for when I could install it. As it happened, John also had loads of other jobs to do, so it sat there for several months, before we could find a mutual time that suited us both, for me to go and collect it.
In the interval, my friend Ross turned up one day, He is a really amazing person, who has so much knowledge and life experience with machinery. He saw me working on some of my ruined gear and asked what I planned for the dough mixer. I told him that I had given up on it for the time being, but couldn’t bring myself to abandon it. Ross had a good look at it and said that he thought that he could extract the main shaft from the gearbox and straighten it in his hydraulic press. He had done other jobs like that in the past. So I said “yes please, have a go at it”. I know that I won’t get around to it for a long time – if ever.
Luckily, I had poured spent engine oil all over most of the machines to stop them from rusting too much and greased all the bearings to prevent them from siezing up, so as to preserve them until I could find the time to get to them and try to fix them. I also bought a massive tarpolin to cover them. This turned out to be a smart move, as they remained there, under cover, for over a year. I found out through this experience that there is a massive amount of condensation under a plastic tarp, so all the machines that wern’t oiled were very badly rusted.
We worked on the dough mixer. Ross and I were able to dismantle all of the moving parts that still moved, and Ross took the main shaft home with him. He called a few weeks ago to say that it was now back in a good shape. Not perfect, but very good. We water-blasted the carcas to remove all the old oil, carbon, ash and burnt paint from it and I moved all the other bits inside, to keep them dry while I set about re-assembling the gearbox and all other moving parts. Ross organised a new oil seal and I had removed the main bearings and soaked it in oil to rinse clean and preserve them.

At this point, it’s looking a bit like a burnt out darlek!

A new 3 phase electric motor, a good clean, some rust converter and a coat of zinc primer and it starts to look as though it will go again.
The mixing bowl on the other hand had copped a bit of a hiding. It was split in 4 places around the rim and was no longer completely round, in fact it was a little bit heart shaped. I spent some time on it, a bit at a time, clamping it back in shape and tack welding it together,  getting it as round as possible, then welding all the splits back solid again.

After a week of nights, doing all the usual things, rust converter, penetrol sealer, zinc primer, several top coats of hard gloss oil paint and its looking great.

Everything is coming together now. The housing, gearbox and mixing arm have been given their severel top coats and are looking good. I bought a new 3 phase motor, new drive belts and electricals, so when I plugged it in the first time, and it actually went – I was really moved that it was back from the dead. Again! Thanks to Ross! 

Now I need a pug mill and we are back in business, ready to make clay again. This restored ‘phoenix like’ twice burnt, and twice restored dough mixer sits in the same room as John Edye’s mixer that I bought when I had absolutely no idea that mine might be recoverable. Hints of ‘two-sheds Jackson’ here. Steve ‘two-mixers’ Harrison.
Weirdly, my old ruined one is now ready to work before I have finally gotten around to finishing cleaning out and painting the bowl of John’s machine.

Rust converter being applied inside the bowl and the mixing arm to neutralise the rust, by converting the iron oxide that is very susceptible to oxidation with air when it gets wet, and converting the iron oxide to iron phosphate, which is quite stable and inhibits further rusting. However. The iron phosphate really needs to be sealed with a water impermeable membrane. In this case it also needs to be fairly impact and wear resistant. I have found that an oil based, high zinc, machinery paint works quite well. Well, similar stuff that I used in 1983, the first time that I restored this mixing bowl worked really well and lasted for 36 years! Of course, there is no guarantee that anything on sale today will last as long.

The bowl after rust conversion. I sent this image to John and we both agreed that the inside looked al to like an ancient ‘hare’s fur’ tenmoku glazed tea bowl.

Ready for the primer and top coat.

The first coat going on.

ready for work.

High hopes are not enough

After I had such a terrible firing a couple of weeks ago. I got stuck in and remade all the work. I’ve filled the shelves and had 2 solar fired biscuit firings and I am almost ready for the third. Then I can pack the wood fired kiln again. Hopefully this time with more success.

I had slaked down all the turnings from the last work session and made half of this work from the recycled sericite bodies. I have made test batches of 5 different sericite this time round. I have 2 Chinese minerals, 1 Korean, one English and one Australian in this batch. Although strictly speaking, the local one is a complex mixture of Illite, kaolinite, quartz and felspar.

I’m always looking for something that I don’t know, so the search is a bit difficult as I’m working semi-blind. I know more or less what I want and how to achieve it. After all, I have been doing this research for the past 40 years and more. But getting what I consider excellent results is always elusive and difficult. It doesn’t help when the kiln shelves break and collapse… Still, I’m over that and all the new work is made and drying. I’m just turning the last of the throwing today.

Sericite is funny stuff. It isn’t plastic like other clays, it’s quite short in most cases and has to be coaxed along to get any height in the form. I learnt to throw the inside of the form as I want it, leaving a thick wall to retain the form without it squatting. I then have to turn quite a bit of material off the outside to realise the finished form from the thick lump at the base.

Although sericite isn’t plastic, it still shrinks quite a lot and has a terrible tendency to crack in drying where it is thick. I have developed a few techniques to cope with theses peculiarities. I’ve learn’t to throw everything on batts, as lifting the pot with my fingers causes a memory distortion in the body that shows up later in drying. I’ve learn to ‘polish’ the out side of the clay after I have finished throwing, to seal any possible defects or weak spots that might start a crack during the early stages of drying and stiffening. I have also learnt to turn the bases in stages. Thinning out the clay as soon as it is stiff enough. This stuff can’t be turned like ‘normal’ clay based bodies. It has to be very firm, almost dry to get a smooth finish. If turned too early, it chips and tears, making an awful mess of the fine surface. It’s a bit like cutting soft goats cheese, it just tears.

Trimming the base of this pot almost bone dry

I’m getting better success rate these days with each variation and improvement of these techniques. It’s a little frustrating to loose so many pots, but they slake down quickly and can be stiffened in plaster tubs out side, then re-thrown within a week.

It would be better to leave the body to ‘age’ in a cool dark place for a month or two, but with so many variations of sericite porcelain bodies in constant testing and development. I’d loose track. As it is I really have to concentrate and keep very good records, marking every bag with a permanent marker, identifying every bucket of turnings in the same way and carrying this over to the slaked recycled material in the buckets and in the plaster tubs. It’s quite a paper trail of provenance, keeping track of it all. I also keep a daily diary in the workshop of what I’m throwing and what I’m throwing it out of. Every pot gets inscribed with the batch of body and later identified with oxide as to which glaze I used. I also keep log books for the glaze and the body ball mills, so that I know what I made, the date it was done, and what it was made from. I always seem to have a dozen different batches on the go at any one time and they all need their own bucket and bag storage space. It’s organised chaos.

I’m nothing if not thorough. I have to be. With over 3,000 glaze tests and hundreds of clay body tests. I need to keep track. I really want to make simple, elegant, beautiful things. But things with a particular character that I admire. Just a little bit ‘damaged’ or altered by the process of their making. Perhaps I should say ‘enhanced’ by its process and journey, plus the unique quality of its material. I like my pots to have a story embedded in their form and surface. I can pick them up years later and ‘read’ that story. I like that.

I’ve just made a few more white tenmoku bowls. They are slightly bigger, fuller and rounder, more generous in feeling, less austere. I haven’t finished turning them yet. They still need more work over the next few days, but I have high hopes for them.

Unfortunately high hopes are not enough. It’s long term, steady, pains taking, thorough and often boring, consistent research that makes progress for me.

That’s really rewarding!

27 Kilns in 27 days – vol 3

Vol. 3. Recent industrial wood fired celadon tunnel kiln.

While in the Longquan traditional celadon region researching celadon, we took some time out to visit a former celadon factory, that was forced to close when the economy was modernised. It has now re-opened as a celadon museum/cultural park.

I found it a bit shallow and lacking in depth. That is to say what was there didn’t grab me. It may be of interest to the more general tourist, but there wasn’t enough there to speak to me, as I’m interested in the more intricate details and technical information/insights that could be included, but weren’t.

However, there was an old wood fired tunnel kiln that had been restored. This kiln was the main means of firing the celadons here right up until 1998. One can understand why it went broke and couldn’t compete with more modern factories with up to date facilities and equipment.

There was also an clay processing section that used the old fashioned water-driven, wooden clay hammers, that is a technology that dates back 1000 years. It was exactly fitted with the age of the kiln technology, So out of date for a factory setting, it is hard to believe that it managed to last right up until the 1990’s.

Clearly, this equipment hasn’t been used for many years, possibly since 1998? Just like the kiln.

All the pots produced in the wood fired tunnel kiln, were packed in saggers to protect the ware from the fly ash from the wood fuel, which is so important when making a subtle glaze like celadon.

It is interesting to see that sometime between 60 and 20 or so years ago, they wrapped some parts of the wooden roof frame with ceramic fibre to stop it singeing or charring during firing.

The saggers that were used in the kiln firings are these days used as retaining walls and breeze way walls.