Hello everyone,

I have had a continuing problem with my cloisonne work cracking and I would love your input, experiences and advice.  Here are the facts:

- I enamel on copper that is 20 or 18 gauge

- The base is dapped for strength

- I use 1 mm fine silver wires; with this size I achieve 4 - 5 layers

- I am counter-enameling.  I know that my counter enamel should be the same thickness as my top enamel

- I use a digitially controlled kiln, usually enameling each layer at 1450 degrees F for 1.15 - 1.30 minutes

- I use both non leaded and leaded enamels, but I am conscious of the order...ie. leaded over unleaded, not the reverse

- I let the pieces cool naturally, once out of the kiln, and never stone them under cool water

My pieces are no larger than 2 inches in diameter. (and usually smaller)  My enamels usually crack in the open areas.  ie...if I created a cloisonne fish, the enamel would crack in the water surrounding the fish.

The cracks do not necessarily show up in the first day...it might several days or even longer.  Almost always they appear in the transparent enamels, but this is not a rule.

Thank you for your help!
Diana

Hi, Diana-
When I've had persistent cracking, I take a lesson from the little bit of glass fusing I've done, and I anneal after the last firing. I put a piece of fire brick on top of my kiln and let it get good and hot. After firing my piece I let it cool just enough to get it off the rack (I fire on mica) and set it (on the mica) on the firebrick and cover it with a preheated overturned piece of ceramic labware I have, an evaporating dish (looks kind of like a crucible). I let it sit and cool down overnight on the kiln. If you find this still cools too fast, I suppose you could put it IN the kiln after the temperature has come down to about 900 - 1000F, turn off the kiln and let it stay overnight. This might work better if it's on a trivet. I haven't done this yet, but that's what I do to the glass. It should help anneal the enamel.

Aloha, Tina

So as you describe the technique, it seems that you all production steps make well. Here possible sources of error you can check. Are alle enamels the same brand? Are all your enamels: Medium Temperature - Medium Expansion enamel for copper, silver and gold? Did you high melting enamel over soft melting enamel melteing or contrariwise ? Did you anneal the metal before enamelling? If it is possible, dome your workpiece a bit. That can cracking prevent. Lead bearing over or under lead free? You can become aware it: Unleaded UNDER leaded. Edmund

Dear Edmund,

Now that I think of my most recent piece (cracked) I'm not sure the enamels were the same brand...and I KNOW I didn't anneal the base copper. I believe all the enamels were the same expansion...but I will check this very carefully in the future. You have given very good advice and I will be sure to check these things. Thank you for your help!

Dear Tina,
What an excellent suggestion! I am absolutely going to try this. In fact, I'm going to refire my current piece (that I thought was finished -- before it cracked!) and see if your method of annealing helps. I have never read of this in any of the enameling books, so it's a gem. Thank you for your help!

Hello Diana,
Sometimes it is really jinxed. I just remembered that you also should anneal the cloisonné-wire, especially if the cracks runs along the wires. And an other reason for cracking could be, the enamel layers are too thick.
Edmund

If you use different enamels you need to know, by testing the expansion of all your enamels! The enamel with the lowest expansion has to be on top! Your metal is the highest expansion. If you mix these in an incorrect order it may take years to crack, but it will crack.

Patsy Croft
enamelinghotline.com

All has been said, perhaps another possible cause is if there are sharp corners in the wires, you can get tension cracks from this in cloisonné and plique-à-jour. But you say the enamel cracked in open spaces.

The most probable cause is that you used different brands of enamels in the wrong order, as has been said.

Dear Edmund,

I think you are right. In the past, I haven't annealed my cloisonne wires...but I will now! And also I will watch the depth of my layers. I am making a 'check list' sheet, so I will better remember these steps with every piece. Thank you!

Dear Patsy,

This is profound information -- thank you! Do you know of a method of testing the expansion? Most of the enamels I buy say, "Medium expansion", but some vintage enamels are 'unknown'. I'd love to know of a method. thanks again!