So every once and a while, the whole pottery thing just needs to throw out a curve ball, today was that day. Juggling chemistry, alchemy and the duties of Sherlock Holmes, coming up with glazes and even simple glazing has a way of going sideways. By looking at the illustration, you can see something is just not right and is certainly not going in the kiln.
So, here is what I know, the glaze in question is a test glaze, made up as a phase two test (1000 grams) about a month or so ago. I had already glazed 4 or 5 yunomi in this exact glaze and fired it in a low-fire, slip ware firing, again, about a month ago. Fast forward to this morning, I decided to glaze up the test yunomi I threw last week, using the same clay and slips I have been using for years. The test glaze in question, stored in an airtight container, is mixed up and I dip three yunomi in the glaze. Minutes later, the crackling appears on the glaze and some pieces of glaze even peel off. The last time I saw this happen was back at CSU when a student was mixing up small batches of test glazes and forgot the main ingredient.
As I mentioned, this glaze has already performed well in the last firing and there are absolutely no variables. So what gives? The formula is primarily three main ingredients; 3110 frit, kaolin and flint and I am somewhat stumped. I once had someone, I forget who, suggest this was a possible electrolytic reaction, but I dismissed this as my science background is somewhat murky and lacking. This formula is an original “book recipe” and now you can see why I tend to steer clear of those. It worked one minute and not one month later.
I would welcome any input or thoughts or similar situations and pending further “clues”, I am going to make up another 50 gram batch and test it in this firing and then will try to test it again in a month. Maybe it expired? I have seen recipes that say; “use as soon as you make it up”, but I have never had a glaze with an expiration date! In fact, I have reconstituted glazes that were dried out and rock hard for as long as 5 years and they worked perfectly fine.
All in all, just another typical pottery Monday.
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