Nehal Posted January 1, 2021 Author Report Share Posted January 1, 2021 On 12/28/2020 at 11:21 PM, Min said: This is called crazing in ceramics, when seen on pots taken just from the kiln it's usually caused because the glaze doesn't fit the clay it was used on. What's happening is the glaze is shrinking more than the clay during the time the kiln is cooling down. The glaze has to "stretch" to cover the clay, this stretching causes the glaze to "tear" / craze. This can work if the kiln thermocouple(s) used to measure the temperature is accurate but the temperature they measure tends to drift as the thermocouple wears. Even brand new there can be differences between the temperatures thermocouples read. Other issue is just going by temperature doesn't account for the heat work done by the kiln. Example would be if you put a loaf of bread dough in a cold oven then turn on the oven to 400F then pull the bread out once the oven gets up to 400 the dough isn't going to be done. Leave it in the oven for X amount of time and the heat has time to penetrate the whole loaf. Granted kilns heat up much slower than kitchen ovens but it's the premise of the heat working on the dough / clay that is the equivalent of what pyrometric cones measure. Cones mimic the clay being fired, they will start to melt and bend once X amount of heatwork is done in the kiln. Thanks for all this info. What should be done to avoid crazing? Link to comment Share on other sites More sharing options...
Nehal Posted January 1, 2021 Author Report Share Posted January 1, 2021 @blackthorn Yeah, I easily found beeswax candles.. Thanks a lot! Not sure about rubber cement. Will try to find the Arabic name for it and try to find it. That's the problem, trying to find the translation and Arabic name for all these products. But, I'm good for now since I managed to find the candles.. Link to comment Share on other sites More sharing options...
Nehal Posted January 1, 2021 Author Report Share Posted January 1, 2021 @Chilly Thanks a mill! I just changed the location. Happy New Year! Link to comment Share on other sites More sharing options...
Hulk Posted January 1, 2021 Report Share Posted January 1, 2021 Hi Nehal, Here's a recent post o' mine: There are several crazing glaze themed threads on this site; try searching craze, crazed, crazing and read on! If you haven't yet found Tony Hansen's website, it's a real treasure, imo (as is this forum, thanks to all the folks who post here); here's his glossary entry on crazing: https://digitalfire.com/glossary/crazing From there, also see his many several articles on evolving low coe glaze recipes, reformulations, comparison of oxides, glaze chemistry and melting behaviours, oxide interactions, etc., etc. You might post the recipe you used, closeup pics of the crazing, and identify the clay as well - for more specific reactions from forum contributors... Here's a few results from this forum: Deep cracks in the glaze - Clay and Glaze Chemistry - Ceramic Arts Daily Community Crazing, Yes, No Or Maybe? - Studio Operations and Making Work - Ceramic Arts Daily Community Another Tony Hansen article Glaze Crazing (digitalfire.com) ...there are many others! Link to comment Share on other sites More sharing options...
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