Hallo Fernando,

All Trish writes , I can only confirm. Here are a few of my thoughts .

I think neither the thickness nor the shape of the caverns cause cracking of the enamel. Also, the counter- enamel should not cause cracking of the enamel.

With a sheet thickness of 1 mm and a pit depth of about 0.5 mm I think, you need no counter enamel.

As long as the enamel is still reasonably liquid it can not crack during leveling of the plate. Unless the melting point of the enamel is so high that the enamel is already fast when the sheet still glows . Another point may be that your planishing tool is too cold, so that the enamel is rapidly cooled down and thereby crack.

Did you use onla one enamel color, or did you underlay it with Flux? If you use Flux under the color enamel it could be that the two emails have different coefficients of expansion. This inevitably leads to cracks.

What can you do?

1) The planishing tool should of a fire proofed stone, or if you use a metal plate , you should a refractory layer , such as a soldering base attach underneath. The soldering base hardly shocking the enamel.

2) The press tool should be well warmed up . At best, you place it on the kiln.

3) You can try to make the piece without counter enamel. . Then the plate bulges during cooling hardly .

4) If you want to use silver , I recommend fine silver. Except for reds and some purples you can apply all transparent enamels without flux .

5) The plate should be fully supported during firing , so it can not sag during firing .

Here is a photo for an excellent firing-rack for plates. Thompson has unfortunately given up the sales of such racks. But maybe you can let it rebuild . Because the rack does not causes scaling , even with frequent use and also does not warp during firing even when cooled , I suspect that it is made of steel alloy SiCromAl . That is a steel alloy containing chromium and aluminum silicium . On the Internet you can find more info on this alloy.

The image of the cock I add to show in order that the shape of the caverns has no effect on the cracking of the enamel. How you can see the cock has both small , acute angled caverns and large caverns of different width and length.

Edmund

   Hi Trish,

   Thanks for answering , I forgot to tell in my first post that I am working with copper plates, I am not using any silver in this process. I think I had read somewhere it was better to anneal the plate before enameling.

I always clean the plates as you said in your post, after annealing them, I always have done  all the process of cleaning it as you have written in your post, even the baking soda neutralization and the rinse after it, before I start enamelling. I also lay down the first layer of clear flux before the colour transparent enamel, in fact the oxides and burning you can see in the second pic under the blues, I guess they appeared because i layed down a very fine layer of flux and I maybe I fired it more time than I should.

Thanks again Trish for the information.

   Hi Edmund, 

   Thanks for answering.  As I have told to Thrish, I am using a copper plates and yes I am firing a layer of clear flux before I lay down the transparent colour enamel, but I thought that since both the clear flux and the transparent blue enamel are from the same brand I wouldn't have any problem. It is nice to know that  the cracking it is not matter of the deep nor the size of the cells.

   About the planishing tool, I will try to build one like you have said, with the soldering base underneath, and warm it up inside the kiln. But the first thing I am going to try is not using the counter enamel in the next plate, since you said 1mm is thick enough. And about how I fire the plate, I have a proofed stone to support the plate, and since it is flat but grooved I put a mica sheet over it and under the plate to have the best support, (Do you think it is enough?). 

Thanks again for all Edmund.

So how do you describe the support of the workpiece, it should be just as good. I would warm up the planisher but not IN, but ON the kiln.
It is quite possible that enamels from the same manufacturer have different coefficients of expansion. So I would test to see if an other flux/enamel combination also leads to cracks.
Good luck
Edmund

Hi, Fernando !

I don't have any solution for you, but I hope you will find it because I find your  project of cells very promising. I am curious to see the continuation ... good luck for your next tries.

Just a question : do you use torch or kiln ?

   Hi Sydney, 

   Thanks for your words. I have done some little works with torch, but now I am working with a kiln, all I have showed here have been done with a kiln.

Fernando

    Ok Edmund, I got it , not IN but ON the kiln. I have also a clear flux from another manufacturer, gonna try it too. 

   Many thanks

   Fernando

   Hi, I have been working in a new plate, this time without enamel counter, it seems to be better to do this way,because the plate almost doesn't bend. But I still have cracks in some cells, they are very fine, the enamel remains perfectly inside the cells but I can see those fine cracks that appear just when the plate  is almost getting the environment temperature. I have also used another clear flux. No matter how many times I fire the plate, those fine cracks always appear. 

I will keep working on it and writing here about the results.

Hello Fernando, now I have not longer an explanation for the cracks. As before, I suspect, however, that the coefficient of expansion is the trigger.
You could still test if the cracks disappear if you counter-enamel the back of the sheet very thin.

Edmund

   Hi again, I'm working with two plates in a kind of champleve, both plates are 1 mm thick (18 gauges). After I etched the plates, I annealed them, then I applied enamel counter in their backs and fired them. Then I start enamelling the etched face, but they always bend, that's not a problem when I  have only fired  the enamel counter, I press the plates and they get flat again. But when I have finished enamelling the etched face, If I press, the enamel starts cracking even when the plate is so hot. To work the plates with the carbide stone I need them flat, and as a finished work they also have to be flat, cause I want to put them on a wood or a stone.

This is the first plate I thought the cracking was also because the size of the cells, so I tried to make them smaller in my second plate.

The second plate, but the enamel is still cracking.

   I wonder if I should work with thicker plates, maybe they would be harder to bend, and I could get them etched deeper or I also wonder If I should try with these 1 mm. plates a thicker layer of enamel counter. Perhaps I am putting a fine layer of enamel inside the cells and I should put more.

   Any suggestion will be welcome. Thanks in advance

Fernando