Nadrali

I did another firing without changing anything and all pieces where fine. The kiln is a top loader and the shelf was near the bottom of the kiln. Going to have to get some more cones to test the temperatures. If it happens again I will try the soak! Thank you

Hi Callie, no chunks in the glaze and only appeared on that one shelf, which is the curious thing. Thanks for the reply.

Hi Babs, thank you for your reply. Did the higher temperature affect the colour at all? The glaze tends to go greener the higher it is fired. Do you remember what temperature and how long a soak? Maybe you could share the recipe?

Hi Mims, thank you for the reply, I will need to do some more firings to see if I can ascertain if any of the above mentioned factors may have affected that shelf in the kiln. The heavy crazing is because it is a raku glaze. We use it for that bight colour it gives. It is used for decorative pieces only!

Photos

Hello, thank you so much for all the replies! Please see the recipe and answers to the questions below. Recipe High Alkaline frit - 100 High soda frit - 100 China Clay - 20 Copper carbonate - 8 Zirconium - 6 Bentonite - 4 cmc 4 Water 300 We also add a tbls of vinegar ................................................................................................ It appears to be some kind of solid crystal in the glaze or on the surface of the glaze. I don't know what caused it in the whole kiln loads. We have three kilns and in one the glaze was coming out fine so I just used that one kin for this particular glaze. It seems to disappear when wiped with a wet cloth and then it is visible again when dry. (Even when wiped with vinegar it does not go) In the 1st photo there is this whitish crystal thing in some areas. I will try to take a clearer photo. The firing temperature is around 1020 c. It is a low fire raku glaze No controlled cooling cycle, the kiln was left to cool on it own. Items are glazed from green All pieces where made, glazed and then fired at the same time in the same kiln. All pieces on one shelf only had the problem, the rest were fine. Not sure why or if that particular shelf was hotter/cooler. I can't seem to upload anymore photos!?!

Hello, We use a high alkaline glaze regularly and today opened the kiln to find all items on one shelf only, had what appears to be scumming on them. (We have seen this before but normally on a kiln load rather than one shelf of items) Any ideas of what caused this_ All items where made and glazed at the same time with the same batch of glaze. Photo 1 shows the pieces with defects and photo 2 the results from the shelf directly below which have no scum...