There are several reasons you could have cracking in your enamels and here are a couple of ideas of how to avoid cracking enamels
The most common reason enamels crack is there is not enough counter enamel on the jewel. Counter enamel is enamel on the back side of the jewel. Your base metal expands as well as the enamel when heated, and contracts when cooled. Without enamel on both sides of your base metal one side is going to expand more causing the opposite side to crack. If enamel is placed evenly on both sides of the metal you can eliminate this cracking. Sometimes this happens as it is cooling, when this happens there is very little enamel on the back. But I have seen the enamel crack years later when the enamel was not even on both sides of the base metal.
In some cases you can also dome a piece of metal and use less counter enamel as in a bead. But if you plan to put a thick layer of enamel on the front of the metal you then need more counter to avoid cracking in your enamels.
Another reason and how to avoid cracking enamels is if you use a hard firing enamel next to a low firing enamel. Hard firing enamels take longer to fire, and low firing enamels take less time to fire. Great reason the make test plates and see when each enamel melts first when they are all fired at the same time on the same plate. 
You can see on my test plate dot #4 is still grainy while the others are smooth. So #4 is a harder firing enamel and if placed next to #5 and you fired it long enough that both enamels were smooth in time the jewel will crack.
Cracking takes place in leaded enamels as well as unleaded enamels. Unleaded enamels are harder firing enamels than leaded enamels so if you combine them on the same jewel you can experience cracking. If you need to use them together use the unleaded first then layers of leaded to avoid cracking.
I’m torch firing opaque enamel in the backside of a piece of copper. Looks good when done but once it cools there are cracks and it flacks off. What am I doing wrong?
Michelle, you need enamel on both sides of the copper piece. It is called counterenamel. If you add enamel to the back side with a little klyre-fire added to your water. Let it almost air dry then add enamel to the front. Very slowly heat with your torch from the bottom staying at least 12″ away. You will see the top enamel fusing, and slowly back off your torch to cool.
Good luck, Patsy
Hi there, I have found that sometimes the backside of my enamel creations needs to be fired again. I am afraid of messing up the front side. Would it help anything to use Amacote on the front while I refire the back? Thanks!
Hi Katie, you will not be able to get the Amaco off your front jewel without grinding it off. We get excited while enameling and forget to counter enamel each time. But I also have to remind my self to counter.
Good luck Patsy
Can I retire a piece that has enamel chipped off probably because the klyr fire wasn’t dry.?
You can re-fire it. try to add a small amount of N4, a flux by Ninomiya, it is a low fir and heals cracks nicely.
Hi there! Thank you for this helpful article! I am trying to make enamel pendants using fine Silver with transparent enamel. I am then wanting to fuse millifiore on top of the transparent enamel but it just cracks off every time. I have not used counter enamel because I like the fine silver backing but I think it won’t work because the millifiore is so much thicker than I could get the counter enamel anyway. Any ideas? Thank you! Joanna
Hi Joanna, Hope you had a great Holiday! Where I would start is to slightly dome the fine silver sheet. Also using a heavier gauge metal helps, maybe 18 ga. If you like the look of fine silver on the back use the clear flux to help balance the expansion and cracking. Next, after firing the millifiores on, if you have cracking, I would sand them down to match the thickness of the back counter enamel. The enamel colors go all the way through the millifiores. Then glass brush well, and let the piece dry before re-firing.
Good luck! Patsy
Greetings- I have a question with which I hope you can help. I recently got my Hidalgo ring back from the company after the enamel cracked and chipped. I am afraid of this recurring, and I wonder if there is anything I can apply to it protect the enamel. I notice that there is enamel only on the outer side of this ring, and after reading your post on cracking, I am really nervous about this ring!
Any suggestions?
Thanks-
Alison
Alison,
The cracking I am talking about in the article is due to the expansion and the metal and enamels not matching while heating in the kiln. The cracking in your ring is from wear. It is the correct tEnamels are glass, and of course when you wear it daily it gets banged around and can crack.
I wear a ruby ring that has small channel set stones that are cracked.
Alison,
The cracking I am talking about in the article is due to the expansion and the metal and enamels not matching while heating in the kiln. The cracking in your ring is from wear. It is the correct thickness of metal to enamels to not crack right away. Enamels are glass, and of course when you wear it daily it gets banged around and can crack.
I wear a ruby ring that has small channel set stones that are cracked. Some people have cracked their diamond rings.
Wear it and enjoy it, and one day it might need to be repaired again.
Patsy