Enameling tool to help you avoid cracks. A                           Digital  Caliper

You can see by these images how the two points of the digital caliper come together to give you the thickness of your enameled jewel. By using this you can determine if  the thickness of the counter enamel is equal to the enamel on the front side of your jewel. It’s not always easy to tell by looking that  they’re the same. Or maybe you lost count as you were enameling if you put the same amount of layers on the back as you have on the front of your enameled jewel. I see often enamelists posting, “Why is my enamel cracking?” It’s usually because the counter is not equal to the front side of your enamel

The jewel I am working on and using the digital caliper to help me as you can see, my jewel is domed.

And with counter enamel the underside of the jewel gets hotter than the top, and often it causes the counter enamel to thin at  the under side of jewel making the sides thicker. This is another real good reason to use a digital caliper.