Thanks so much for these two suggestions. If anyone else has another technique, I would be glad to read it. I am writing on behalf of a friend, so I am not sure what kind of equipment she has.

Pat

Hi Pat,

here: http://blog.vickiehallmark.com/2011/09/removing-vitreous-enamel.html is a description how to  remove enamel.

Friendly 

Edmund

Dear Edmund,

What an interesting article. Could I post the link to your blog on the British Society of Enamellers' Facebook page?

Thanks very much,

Pat

Dear Pat,
it is not my blog. But because it is an public Internet page, it is not a problem, to publish it at the Enamellers site.
Friendly regards
Edmund

Just a word...some people have found the cream of tartar/salt method can be messy in the kiln.  Try it with the torch heating it from below on a stand.  It works fine that way and you won't have any clean up.        vera

I've used Etch-all to completely remove the glass from a cloisonne piece.  (I wanted to recover the 24K gold wires I'd used...)

I did take about a week though.  I just put the pieces in a Tupperware container, and covered them with the Etch-all.  About once a day, I'd give everything a rinse and a stir, and it really did work like a charm.

You can see the process on my blog:

http://sandramcewen.blogspot.com/2010/07/fun-with-rejects.html 

I do appreciate all of these responses. I am going to put them together in one document and post it out to the members of the British Society of Enamellers. It is wonderful that there are so many different ways to remove enamel.

Cheers,

Pat

You can use hydrofluoric acid bath, much attention is very corrosive!, use a plastic container, rubber gloves, and goggles.or if you have a micro-sandblasting machine with aluminum oxide sand 90 microns

We should never recommend hydrofluoric acid for removing or etching of enamel surfaces in thisforum. In lay hand it is one of the most dangerous acids. Even a short skin contact with hydrofluoric acid cause deep burns that can go through to the bone! These burns are always very painfull and they heal very poorly.

Edmund

I agree, in fact I have warned of the dangers and precautions

I am glad to have these posts that mention of hydrofluoric acid so that I can add them to my little article about removing enamel from cloisonné work. People will come across one way or another so it is to have some information and precautions about this acid's use. 

There is of course no objection if a professional uses hazardous chemicals.
But the chemical layman should look at these pictures, before he resorts to Hydrofluoric acid.

Klick to the link:
http://search.snapdo.com/?q=chemical%20burn%20as%20hydrofluoric%20acid&start=21&category=Images

Edmund

So that you can see that I did not want to play the devil's advocate, I recommend the skeptics reading "Health and Safty" in the Wikipedia article: "Hydrofluoric acid". To read the article, click here:

http://en.wikipedia.org/wiki/Hydrofluoric_acid

To etch away  enamel from a workpiece worth only if a lot of gold was used in the work. For copper, it is easier and faster to throw the pieces into the garbage and to make new one. Corrupted  Silver workpieces are added in the silver waste to be sent to a refinery.
Enamel can also be  removed of a workpiece if you heat up the workpiece to red heat and immediately throws the piece into a container with cold  water. A large part of the enamel jump away and the rest can be removed mechanically mostly.

Dear Edmund, as per your links it looks like you have a Search Snapdo rogue search engine installed on your PC. I recommend resetting your browser, or removing it manually as it can steal your credentials and show unsolicited ads, and possibly redirect to dangerous websites: http://removal-guides.com/malware/search-snapdo-com/

Hi Max,
because of a hospital stay I can answer just today and  to thank you for pointing out . As soon as I'm fit again, I'll reconfigure the PC.
Thank you very much
Edmund

Does anyone know how to remove glass from a piece of cloisonné that has gone wrong, so that enamelling can start afresh?