Why is the enamel cracking?

[Luci]

Hi all I hope some one can give me some advice on enamelling?
Having not done any enamelling since collage I have started playing around with it again but I think I must have forgotten something because the enamel keeps cracking?
It’s just on a silver (silver clay) disc with a recess so nothing really complicated!?
I don’t have a regulator on my kiln, is it possible to get one to add on?
Last question!
Can I remove the enamel from the silver and how do I do it?

Thank you.

[ps_bond]

From my limited experience with enamels... Does it need counter-enamelling? Is it being cooled too fast? Is the layer too thick?
As for complete removal, some severe thermal shock might do the trick - stick it into some water once the metal stops glowing. Stoning the enamel off is more subtle though.

[FVT]

I'm by no means an expert, but have been trying my hand at enamelling for a while now.

Re: the cracking...the most obvious cause that was explained to me is if you cool the piece down too quickly..try leaving it in the kiln for a while after switching it off. Or, if torch firing on steel mesh (like I often do) don't remove it from the mesh straight away, let it cool down as slowly as possible.
You can also get cracking depending on how many layers you are adding, the more layers, the more likelihood of cracking I've been told. If the layers aren't quite smooth enough, you may get air bubbles etc which wouldn't be helping.

Re: removing enamel, there is a method that involves mixing salt and cream of tartar and refiring it....this is described in a great book called Enamelling on Metal Clay by Pam East. I'm not sure if the forum rules stretch to me copying it out here?!

[ps_bond]

That rings a dim bell - the only chemical way I could think of was molten alkali... Worth a precis at the very least - a description of the method shouldn't constitute any breach of copyright.

[mizgeorge]

This was described in article by Pam East in the July 2009 issue of Art Jewelry

Mix equal parts of table salt and cream of tartar, then add enough water to make a thick paste.
Apply this paste thickly to the enamel
Place on a bit of old mica reserved only for de-enamelling and fire at 788 degrees C for 2-4 minutes. It will produce smoke.
Drop into cold water whilst still glowing hot. On contact, most of the enamel and residue will break away, any remaining can be chipped off.
Scrub with steel wire and soapy water.

The process may need to be repeated more than once for thick enamel.

[MuranoSilver]

There's a book by Pam East called Enamelling on Metal Clay in which she suggests using a cream of Tarter /Salt mix
to remove the enamel (might be worth having a read of that)
Re the cracking could be lots of reasons - how thick is the piece?
Normally when enamelling I make mine at least 4-6 cards thick +the edge, having a slight dome to them will also help
Nic x

[arian]

I think it should be counter-enamelled.

Leave it on top of the kiln before firing to make sure the enamel's
perfectly dry, and again after firing so it doesn't cool rapidly.

Edit: Been thinking about this, and if the enamel is cracking off,
then the same thing would happen to the counter, so maybe that's
not the main problem. I still think the piece should be counter-
enamelled, though.

Oppi Untracht's Enameling[sic] On Metal suggests:
1) Enamel too thick or uneven. Especially on flat pieces not counter-enamelled.
2) Too sudden cooling of transparents.
3) Sharp right angles may cause cracking at the angle.

[Luci]

Thanks everyone I will try that tomorrow.

[caroleallen]

If the silver is thick enough you shouldn't need to counter enamel as long as the layer of enamel isn't too thick. If it cracks, try rubbing it back and fire it again.