It’s that time of year again. I need to make some more wadding for packing the kilns. Making wadding isn’t fun. It isn’t even interesting really. If truth be told, it’s a rather dull job. It just has to be done. So, to make it as bearable as possible, I make it up in a monster size batch, so that the pain is all in one go and then there is the relief of knowing that it won’t need to be done again for another year.
Wadding is used to seperate the pots from the kiln shelves and the kiln props from the kiln shelves. It has to be refractory and remain crumbly and friable after being fired to stoneware temperatures, so that it can be removed easily, even allowing for the deposition of the fluxing effect of wood ash during the firing.
I make it up in big batches of 120 to 150 kilos. Every wood-firer has their own ‘secret’ recipe. I don’t have any secrets. They’re all up here on this blog. Some potters use various mixtures of silica and clay, but I don’t want to use fine silica dust anywhere if I can help it, because of the risks of silicosis. Others use alumina powder and clay, which is very refractory, but expensive and in my opinion it is overkill. There is too much of an embedded energy debt tied up in aluminium and alumina processing. It takes massive quantities of electricity to extract aluminium from bauxite, most of which comes from burning coal, so it is rather unethical to use alumina powder, unless it is absolutely necessary. We use a small amount in shelf wash, but it amounts to just a kilo a year. I can live with that. The other thing that I really dislike about alumina in wadding is that unless you are particularly careful, you end up putting stark white finger prints on the pots that are being packed after handling the wadding. You really have to wash your hands after every time you touch the stuff.
I have decided to make this batch of wadding out of ‘fat’ sand. Fat sand is also called ‘bush sand’, ‘brickies sand’ or ‘bush loam’. It’s a coarse quartz sand with a fair amount of clay in it. It also contains some limonite or hydrated iron oxide, so it looks a bit yellowish. I mix this with some powdered kaolin. This is a great use for powdered kaolin. I don’t use a lot of it, but is is very useful for this purpose. I mix it in the ratio of one 25kg bag of kaolin to 4.5 buckets of damp washed sand and one bucket of water. When I can get clean saw dust I also add two buckets of saw dust, but this is getting harder to find these days. The last time I visited the local timber yard, they had been cutting some synthetic wood products that were a rich canary yellow. This stuff looked like it was loaded with resin glue. I thought that it might be particularly toxic if it were burnt in the kiln as wadding. So I didn’t collect any. So, this batch of wadding is just going to be sand and clay.
Adding saw dust is great for wadding that use on new pots that are once fired, as it can leave an interesting charcoal grey to black shadow mark. It doesn’t work on bisque, only once fired work.
When it is freshly made wadding like this is rather short or non-plastic, being so sandy, but after ageing for a few months it develops quite good plasticity and after a year or so, the last few bags are plastic enough to throw with. Not that you would want to, but I think that it might be possible. I’m down to my last bag of the old batch now and it is very easily worked into coils and small balls. This new batch will have a month or two before I need to use it.
I make it up in a couple of batches in the dough mixer and then bag it up into 15 kg packs and store it away.
Security is a years supply of wadding. Now, when I look down on my stash of wadding I get the simple pleasure of knowing that I won’t have to do this job again for another 12 months. It’s a nice feeling!
fond regards from the well wadded potter.