Zuri Posted January 24 Report Share Posted January 24 Hi! I have a question about Lavafleck clay which I use. Recently I've been having too much crack on my cups while customers using especially at restaurants and coffee shops. I don't have that before everything is same didn't change for years, 940 bisque and 1240 glaze firing. What might affect this event? Do you have any recommendations for firing and making the result much stronger? Quote Link to comment Share on other sites More sharing options...
Min Posted January 25 Report Share Posted January 25 Hi Zuri and welcome to the forum. I looked up the Lavafleck and see that it has a firing range of 1200 C - 1270C. Clay is at its strongest when fired to maturity so if possible I would suggest raising the 1240C that you currently fire at. (and adjusting glazes as necessary) Quote Link to comment Share on other sites More sharing options...
PeterH Posted January 25 Report Share Posted January 25 15 hours ago, Min said: I looked up the Lavafleck and see that it has a firing range of 1200 C - 1270C. Clay is at its strongest when fired to maturity so if possible I would suggest raising the 1240C that you currently fire at. (and adjusting glazes as necessary) +1 I found a potclays-clay-analysis.pdf file on the https://www.bathpotters.co.uk/ site. https://www.bathpotters.co.uk/userfiles/file/potclays-clay-analysis.pdf ...which gives vitrification range 1250-1280 & firing range 1200-1280 PS Finally found it on the Potclays site. Click download file in the Clay Analyses box on https://www.potclays.co.uk/Technical-Information Quote Link to comment Share on other sites More sharing options...
Zuri Posted February 2 Author Report Share Posted February 2 (edited) Hi! thank you for your answers. I tried 1250 and cups and thrown plates look much better now but I have small hand-shaped quite thin saucers and they are all bloated both glazed pieces and non-glazed ones. I have bloating areas on some cups as well. Do you think because they are too thin and that causes the bloating? The saucers on the very top layer of the kiln have less bloating. My bad I didn't use any cone because that was the second fire and on the first one I didn't get any bloating I used cones on the first fire and they all seemed to me right. Edited February 2 by Zuri Quote Link to comment Share on other sites More sharing options...
Min Posted February 2 Report Share Posted February 2 I would verify with cones. You could fire the kiln with shelves (and some extra posts for mass) but without pots to calibrate firing with the cones. Is the design of the pieces part of the problem of chipping? Where are the pieces chipping, rims? Quote Link to comment Share on other sites More sharing options...
Zuri Posted February 3 Author Report Share Posted February 3 Yes, they are also chipping from the rims. Maybe I could try a long soaking at the beginning, I only do 30 minutes of soaking at the moment. Quote Link to comment Share on other sites More sharing options...
Min Posted February 3 Report Share Posted February 3 (edited) 5 hours ago, Zuri said: I only do 30 minutes of soaking at the moment Are you soaking at the end of the firing? If so a 30 minute soak is going to add a lot of heatwork which could be making the clay brittle. Could you post a couple pictures, including the rims? When you say you could try a long soaking at the beginning what do you mean? edit: for sure it's not glaze shivering? Edited February 3 by Min added a thought Quote Link to comment Share on other sites More sharing options...
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