its happened to me also... i put about 10 earings and 5 rings into my kiln. i decided 270 was fair enough as i had alredy cured resin for about 2 hours in a double box uv light setup. so i gave it 2 hours at 270.
i had some flowers and ---some of the top flower layers cracked and flaked . The thicker rings one of them had a fine crack going through the top. i super glued it and then melted some wax on top.
i have noticed the best way is to leave in uv box for about 6 hours or so...o direct sunlight i have a mirror box i put that under the sun for a whole day. I dont use the kiln to fast cure stuff anymore until i understand why u have a 50% of cracking prone to happen,,, i just casted some earings . Tjas ive seen ure other post on casting.
i also use satin cast but my flask are about 4inch in daimeter and 2.4 inch in height.
i have tried to raise temps slowly i start at 250 one hour 300 2 hours.* to get rid of water in investment*********- 700 2 hours 1350 2 hours
1000 2 hours ---then cast/// results sometimes vbery good this time around i had a few imperfections. il post some pick later on ..
Theres no doubt in my mind u need to get rid of that water in investment slowly... but after that do u raise temps like to 1350 for more than 2 hours...I know u use smaller flask than i do but i would like 2 know ure burnout cycle. I have also done test using rio grandes vacu film prior to investing, krylons plastic finish, even brushing rcherry red to get smoother finish then light curing... but its that dam burnout i cant just get right.
any info would be greatly time saving fo me --Tajs throw me some info. thanks,