What is the difference between regular glazes and enamel used on jewellery, could someone explain? Thank you!

[simon7]

Hello everyone, i would like someone who knows very well to explain pretty please the chemistry, the ingredients, and the difference between regular pottery glazes and vitreous enamels used on metal jewellery,  im scratching my head, whats the difference?  i know one is low temp the other a high, but specifically what ingredients differ from eachother?  i know "glazes" is a broad term, because there is a lot of them, but in general.  Thank you in advance for your time. 

Simon

[simon7]

Im asking this question because i would like to make my own Enamel for jewellery if possible, its expensive :S if its simple ingredients i could get from a pottery arts shop i could make it, if someone knows well, would be appreciated. thank you

[Dick White]

The obvious main difference is melting temperature. Do you know what temperature your enamels are melting? I don't know of any enamel recipe books, but with the slight amount of enameling I did with my Mother years ago, the enamel powders were previously melted glass ground to a fine powder. I doubt that conventional glaze raw materials would work at the low temperature; the various materials melt at different temperatures and so you have to take them to a fairly high temperature for them to melt together into the vitreous glass. Whether you could fake it with ordinary Mason stains, dunno but might be worth a try since you already have the equipment for enamel work.

[Hulk]

The enamel also has to stick to the metal substrate - well enough to go through the firing, and particularly, afterward whilst in use.

Kitchen appliances, many of them used to be enameled (still are), and enamelware pots and pans are still being made...
I'm not finding recipes, maybe this book Enameling with Professionals;
this article, perhaps for background and detail on materials Materials and methods used in the manufacture of enameled cast-iron wares. (nist.gov);
and, for "this" III, a site replete with many links, see Library -> holdings, links under Resources, etc.
The Enamelist Society Inc.

Interesting.
The materials should be findable, one might have to look harder than I did to find formulas, however, how would one go about grinding up the result, previously melted glass, to the fine powder? Hmm, if one had a kiln, crucible, crusher set up, and a ball mill...

added: being curious, was reading that second link; most all the formulas include lead. Hopefully, modern enamels use other oxides...

[simon7]

Thank you Guys for your time Thank you Hulk for looking into the matter and being kind enough to share the article, very interesting.  I bet today they wont use lead because it would leach out from ware. Have a nice day! 

[Hyn Patty]

My understanding is that once lead is firing into glass, crystal, or glazes it is no longer a health hazard.    After all, lead crystal has lead in it but it is food safe.  There are however other things in enamels that can be very food unsafe so still use with care.   Also here is a quote I found online to give a little more detal:

'

• The answer is both yes and no. Glaze often contains lead. Lead fuses glaze particles to pottery during the kiln firing process. If glazed ceramic pottery is fired at the correct temperature for the correct amount of time, the lead glaze will fuse to the pottery and the material will meet leach test standards – and be safe for food.

[Callie Beller Diesel]

The difference between things like glass, glaze and enamel mostly boil down to the proportions of the ingredients used. They’re all some combination of silica and various fluxes to make them melt at different temperatures, with ceramic having some alumina thrown in as well. But it’s like the difference between bread, cake and cookies. They all have similar ingredients and need baking, but they wind up being different in the end.

The different combos of the same materials do lead to important differences in things like coefficients of expansion, which lead to assorted flaws or beneficial effects in each of the materials. What may be desirable in one isn't in another. It can also lead to significant differences in firing temperatures. Enamel is on the lower end if you’re looking at melting points only, with glass batch next, and the majority of  pottery glazes will be on the hottest end. There is some overlap, and variance with different techniques. 

If you want to know more about enamelling in jewelry in metalwork, I’m going to point you at ganoskin.com. It’s the jewelry version of Ceramic Arts Network, and they have over 100 articles and videos on enamelling alone. One of the founding members of Ganoskin was an instructor in the jewelry department of my alma mater, and he’s one of the most generous teachers I’ve ever encountered. This article gives some description and an overview of what enamelling is, and seems like a likely place to start. https://www.ganoksin.com/article/origins-evolution-practice-enameling/. They also have some good health and safety info there.

A quick search for materials does show that lead free cloisonné enamels do indeed exist. They likely have their own hazards, and I’d get some MSDS sheets and make sure you know how to handle them safely. 

 

14 hours ago, Hyn Patty said:

. If glazed ceramic pottery is fired at the correct temperature for the correct amount of time, the lead glaze will fuse to the pottery and the material will meet leach test standards – and be safe for food.

There’s a LOT of “if” there. It’s not just the temperature, the chemistry of the glaze needs to be balanced properly, and the kiln firing needs to be controlled very exactly to ensure the glazes are thoroughly and properly melted. And you have to be able to replicate all of that through equipment wear and tear, and any raw material composition drifts. Lead is also volatile, and leaves residue in the kiln. I personally know people that have had to go through lead chelation therapy in a hospital because the paint your own pottery place they were working at fired the kilns while workers were present, and the owner used a commercially prepared lead based clear. This was 20 years ago now, and that glaze isn’t on the market anymore. But there’s a reason for that. 

While it is possible, it tends to be beyond the skill level, kiln firing accuracy, or access to testing for most of the folks that come to this forum seeking advice. Lead is one of the 2 materials that has current leachate regulations attached to it in North America and I think the EU is looking at bringing in even more regulations for pottery in the near future. It’s too hazardous for us to recommend using lead in small business/hobby/art ceramics practice. Jewellers are going to be subjected to their own best practices, and again, I think Ganoskin is probably a better place to check for specifics on that. 

[Hulk]

The materials and methods article I linked earlier, I though interesting, particularly the feldspars, crazing, and process chapters, however, the Enamelist society link likely more current, helpful and specific for OP:
The Enamelist Society Inc.

The former indicates use of lead in many of the formulations; note the publication date 1919.
No way I see lead in any kind of everyday use.

Just saying, respectfully!

And seconding
a) that safe use of lead - in the studio - a separate topic from use of the ware, and

b) safe formulations including lead have to do with formulation, not just heat work, "The solubility of the fired glaze is dependent on its chemistry and the way it is fired." credit Tony Hansen for the quotation.

What's the acceptable lead limits these days (last ten years or so)?

added: having read reference to CDC stance on lead limits being none - no safe level of exposure being identified - yesterday, went looking for the actual language and found:
"No safe blood lead level in children has been identified."

added ii: having read more from CDC ToxProfiles docs, although chapter seven has a table with lots of numbers, that's defining where the law kicks in. There is no "minimum risk level" (MRL) defined for lead; in the appendix A of 2020 Toxicological Profile on Lead Toxicological Profile for Lead (cdc.gov) 
"Exposure thresholds ...have not been identified (i.e., no safe level has been identified) ...MRLs for Pb have not been derived."

'k. Meeting the regulations - how much lead, not same as how much is safe, there is no such number (it, the cdc, doesn't actually say zero).

[simon7]

Wow just wow, thank you all for your generous inputs. It is much appreciated from all of you, now im swimming in knoweledge. Thank you!!