My student is hollow forming pods and soldering them together with extra hard solder, then enameling. Went fine last semester, but they are having an issue with the enamel cracking just out of the kiln. We made a small “housing” of firebricks so that they cool slower, but about every 3rd one cracks off. I am attaching a picture. Enameling is not my highest skill so other than clean metals, cooling slowly and thinnner layers I’m not sure what else to suggest.