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Lead Glaze Recipes (No Safety Lectures Please)


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This is my first post to the forum.

 

I am a ceramic sculpture working with exotic and sometimes controversial metals.  I am also an experienced chemistry teacher with a BS in chemistry.

 

I am well aware of the health concerns related to using lead as a glaze ingredient.  I take the appropriate precautions so please save your time if you are going to lecture me about safety or try to convince me I shouldn't use the material.  My work is strictly sculptural (display wall pieces) and I make the presence of toxic chemicals in my surfaces very clear to potential buyers.  I am not interested in anecdotal opinions about lead use and the dangers of lead.

 

My studio has a kiln specific for use of toxic chemicals so these concerns are also accounted for.  

 

I have a number of collected recipes for use of white lead along with successful tests.

 

My current interest is in red lead and yellow lead chromate both of which I acquired earlier this week.  Before I start my tests I wanted to see if anyone in the forum has proven results using these materials and their use in color development.

 

Low-fire cone 08-04.  Oxidation.

 

In particular I'm looking for experience with sodium uranate oxidation color development using lead in low fire ranges.  I've also heard zinc and selenium can be used along with lead for Uranium color development.  I possess and am currently using sodium uranate in my glazing so safety lectures about this material can be avoided.  

 

The google searches I've done on these topics are dominated by the theme of safety and not glaze recipes, my primary interest.

 

Thanks for the support.

 

 

 

 

 

 

 

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Sorry, I have to say this.     This post right here is why ceramists don't openly talk about lead.  The reality is that lead produces a superior earthenware glaze.  High gloss, easy melt, simple for

Wish you wouldn’t.   I for one would most welcome more of your posts on these forums. It’s a joy to read your intelligent comments.  

Like the stuff they enrich for nuclear power? You must know some important people.

I have a personal connection that has allowed me to acquire various types of lead compounds.  Sodium Uranate is a sodium salt of an uranium oxyanion (uranium oxide polyatomic ion) commonly called yellow uranium oxide.  Again, my acquisition of this material is through a personal connection.

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Ah sorry, yes, don't mind where you get it. I was wondering if you are using a lead oxide, some sort of frit or other to source the PbO

 

Pure PbCO3 (carbonate),  Pb3O4 (minium) and PbCrO4 (chromate or Yellow lead).  I am not working with Pb frits, but the actual compounds themselves.

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Sodium Uranate is a sodium salt of an uranium oxyanion (uranium oxide polyatomic ion) commonly called yellow uranium oxide.  Again, my acquisition of this material is through a personal connection.

 

Like the stuff they enrich for nuclear power? You must know some important people.

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Don't know if this will help or not, but when I was at Herron School of Art we had a wonderful library, maybe if you were close to an art school that had a library you could go in and check out glaze books which were printed before the time lead/uranium substances became such  controversial glaze ingredients.  You may find some information useful there.  Sorry I can't help you with actual accounts,  when I used Uranium-based components it was 30 years ago, but I will go check my notebook from then and see if I can dig anything up for you.

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Guest JBaymore

Jon Singer is a person you likely want to talk with. You likely will "speak the same language" at a technical level.

 

I use to use uranium compounds in salt glaze "back in the day".  Wonderful yellows and oranges.

 

best,

 

..................john

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I appreciate all the feedback.  I purchased a copy of 1951 Parmelee which has some good information.

 

I will reach out to Singer this fall.

 

I got some interesting results I will post on my website in the coming weeks:  www.andrewirvineart.com

 

My show opens this Friday, 9/4/2015 if anyone is in the San Jose CA area.

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  • 3 weeks later...

I've used red lead lead in glazes - I was testing for differences between it, lead bisilicate and lead sesquisilicate (adjusting the silica in the glaze formula accordingly), and didn't find any. As you probably know, the lead frits were developed so the lead was encapsulated in the frit, and so when the dust is ingested in the pottery the lead is not deposited in the body. The bisilicate makes the lead less soluble than the sesquisilicate (though some can still dissolve out of the frit over time).

 

As you'll know from your work to date, you get good bright colours with lead, plus a smooth glaze that can be very glossy if you want. A useful book on colours is Ceramic Colours and Pottery Decoration by Kenneth Shaw, published (in the UK) in 1962.

 

e.g. for lead chromate (PbCrO4.Pb(OH)2) it talks about chrome reds:

Boiling lead chromate with dilute caustic soda tuns the colour from yellow through pink to bright red - known as coral red.

The flux or glaze it is used with must be high in lead to avoid decomposition to chromium oxide.

Red chromium oxide glazes have a high tendency to crystalise. To avoid this, they need rapid firing and cooling. (Although seldom a problem now, sulphur atmospheres change the colour to grey).

It also says using lead chromate in a basic flux gives opaque Coral red, so the caustic soda may not be necessary with these glazes, whereas an acid flux gives a transparent yellow.

The following glaze is given  as a base glaze for cone 01: 0.752Pb, 0.065 K2O, 0.183 Na2O, 0.06 Al2O3, 0.065 Cr2O3, 0.316 SiO2, 0.1 SnO2

 

And there is more on colours with lead, selenium, uranium etc - much of ot os written on the assumption that you can do basic chemistry to make your colours rather than just buying a bottle or mixing raw ingredients.

 

There is also Weyll's book, which is meant to be good but I don't have a copy of.

 

Regarding uranium, it is perfectly legal here in the UK to have up to 5kg of spent uranium or related compunds, without any licencing or anything. The health hazard is to your liver and kidneys, not any paranoia bout radiation (the word spent may be the clue). The problem is sourcing it - I found one supplier in the Czech republic, who supplies it to glass manufacturers, but didn't get a response to my e-mail enquiry.

I personally have absolutely no problem with people using these materials so long as they are intelligent enough to know the risks and take the safety precautions they decide are reasonable. The problem is people not knowing the risks.

 

Whilst in England there were 400 deaths/year from lead posoning amongst the potters (when they were doing things like sprinkling galena powder onto pots to make a glaze), after the introduction of frits and other sensibvle health and safety measures the deaths dropped to pretty well zero. Subsequently in the USA when it was first mooted to introduce similar measures, the manufacturers made all sorts of claims about how it would bankrupt the industry, which of course it didn't.

 

As far as the user of the product is concerned, the risks are pretty well zero so long as it is a well developed glaze and, in the case of lead, has no copper in it. I don't believe there is a single record of a death of someone using ceramics with a lead glaze due to lead poisoning.

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As far as the user of the product is concerned, the risks are pretty well zero so long as it is a well developed glaze and, in the case of lead, has no copper in it. I don't believe there is a single record of a death of someone using ceramics with a lead glaze due to lead poisoning.

 

The risks of eating from lead based glazes are real. Just because something doesn't kill you doesn't mean it's not bad for you. There are numerous health concerns from lead exposure. For instance, children suffer all sort of developmental problems from lead.

 

Here in the US:

  • Dishware leaching lead above 3 ug/mL of lead is banned under FDA rules.
  • Dishware leaching lead between 0.226 ppm and 3 ug/mL of lead can be sold in California only with a warning label.
  • Dishware leaching less than 0.226 ppm of lead may be labeled “lead safe.â€
  • Dishware should be labeled “lead free†only if it does not contain lead.

If you plan to sell functional works that contain lead, you need to get them tested first. For decorative works, you should still label the piece as containing lead, because the customer deserves to know. And you better have good insurance.

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Sorry, I have to say this.  

 

This post right here is why ceramists don't openly talk about lead.  The reality is that lead produces a superior earthenware glaze.  High gloss, easy melt, simple formulations, easy to get fit, and plays well with colours.  Not to mention superior opacity and whiteness in white tin glazes.  Aside from the toxic effects, I can see literally no downside to lead as a glaze component.  And in that way, it's the opiate of the ceramics and glass industry.  It was (re?)introduced to Korea by the Japanese and it took forever to get it out again.  The guy who introduced a borax alternative in Korea was sued for endangering the public.  The suit was baseless, but it reflects how the industry took it.

 

Ever wonder why there's not been a lead ban for dinnerware, just regulations on its leaching?  It's because it's just too darned useful economically.

 

So rationalizations come about, and those rationalizations don't really go away with the mention of government safety regulations.  It's true that fritting lead eliminated deaths from acute poisonings, but chronic lead poisoning is still an issue.  Chronic lead poisoning isn't observable by the individual in the same way that acute lead poisoning is, either, so it's easy for the individual to misunderstand lead safely based on experience alone.  It's the same as with silicosis and other illnesses of long term exposure, there's no one event to point to a cause, so it's hard to internalize the dangers of the material.  Eating your morning fruit salad out of a lead glazed bowl every morning for life may not kill you, but I'll guarantee you'll have a lot fewer working nephrons in your kidneys at 65 than you did at 20.  And if you did that as a child, you'd have shaved a good number of IQ points off your score.  In fact, neighbourhoods with lead pipes have been linked with increased criminality and lower life satisfaction scores.  At every level of exposure, lead's causing problems.

 

I apologize for singling out the post, but this is why there's so much misinformation and awkward silence when it comes to lead.  It's just as useful as it is dangerous, and its utility makes excuses for the dangers.   I'll retreat back to the woods, now. ;)

 

  

 

 

I've used red lead lead in glazes - I was testing for differences between it, lead bisilicate and lead sesquisilicate (adjusting the silica in the glaze formula accordingly), and didn't find any. As you probably know, the lead frits were developed so the lead was encapsulated in the frit, and so when the dust is ingested in the pottery the lead is not deposited in the body. The bisilicate makes the lead less soluble than the sesquisilicate (though some can still dissolve out of the frit over time).

 

As you'll know from your work to date, you get good bright colours with lead, plus a smooth glaze that can be very glossy if you want. A useful book on colours is Ceramic Colours and Pottery Decoration by Kenneth Shaw, published (in the UK) in 1962.

 

e.g. for lead chromate (PbCrO4.Pb(OH)2) it talks about chrome reds:

Boiling lead chromate with dilute caustic soda tuns the colour from yellow through pink to bright red - known as coral red.

The flux or glaze it is used with must be high in lead to avoid decomposition to chromium oxide.

Red chromium oxide glazes have a high tendency to crystalise. To avoid this, they need rapid firing and cooling. (Although seldom a problem now, sulphur atmospheres change the colour to grey).

It also says using lead chromate in a basic flux gives opaque Coral red, so the caustic soda may not be necessary with these glazes, whereas an acid flux gives a transparent yellow.

The following glaze is given  as a base glaze for cone 01: 0.752Pb, 0.065 K2O, 0.183 Na2O, 0.06 Al2O3, 0.065 Cr2O3, 0.316 SiO2, 0.1 SnO2

 

And there is more on colours with lead, selenium, uranium etc - much of ot os written on the assumption that you can do basic chemistry to make your colours rather than just buying a bottle or mixing raw ingredients.

 

There is also Weyll's book, which is meant to be good but I don't have a copy of.

 

Regarding uranium, it is perfectly legal here in the UK to have up to 5kg of spent uranium or related compunds, without any licencing or anything. The health hazard is to your liver and kidneys, not any paranoia bout radiation (the word spent may be the clue). The problem is sourcing it - I found one supplier in the Czech republic, who supplies it to glass manufacturers, but didn't get a response to my e-mail enquiry.

I personally have absolutely no problem with people using these materials so long as they are intelligent enough to know the risks and take the safety precautions they decide are reasonable. The problem is people not knowing the risks.

 

Whilst in England there were 400 deaths/year from lead posoning amongst the potters (when they were doing things like sprinkling galena powder onto pots to make a glaze), after the introduction of frits and other sensibvle health and safety measures the deaths dropped to pretty well zero. Subsequently in the USA when it was first mooted to introduce similar measures, the manufacturers made all sorts of claims about how it would bankrupt the industry, which of course it didn't.

 

As far as the user of the product is concerned, the risks are pretty well zero so long as it is a well developed glaze and, in the case of lead, has no copper in it. I don't believe there is a single record of a death of someone using ceramics with a lead glaze due to lead poisoning.

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Tyler brought up my own lead history thoughts.

Back in the early 70's we at collage used white lead in many raku glazes--It was a dream flux material. I used to mix those glazes. As time went by it was disued as as a nasty ingredient as the dangers out wieghed the benifits. About 10 years ago I found I still had a 25 # bag of white lead.

I took it to our annual toxic cleanup. I had stopped using it in the late 70's. In my life it went away from gasoline and slowly in my solder for copper work (sweating copper pipes) and glazes. Lead works great in glazes and those subsitutes are never the samebut the handling risks for me are just to high. I love my red lead paint (same as the Golden Gate in SF had). I used to paint in on my metal sculptures(mobils). I turned the gallon of paint in long ago. I still have a few lead raku pots-they where the best.

I have worked with ceramic materials a lot for over 40 years now and lead I'm glad is one I gave up long ago.I still have a few really nasty ones for fuming but its a rare use these days.

Mark

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Omg, red lead glazes make me salivate uncontrollably. That rich color, hnnghh...

 

But, hey! Drooling aside, I have a GREAT old book from the 70s (1st edition in 1949) that has a buncha lead recipes in it that are JUST GORGEOUS. Dunno if you have looked it up or not, but it's called "The Complete Book of Pottery Making" by John B. Kenny. It's mostly a beginner book, but the lead glazes in there are simply scrumptious! Definitely worth looking into.

 

Man, lead carbonate is so beautiful. If you get a big enough chunk, you can cut it like a diamond, and OH dat bling... ^_^

 

-Guinea Pig

 

P.s. Welcome to the forums! You have no idea how happy I am to FINALLY see another lowfirer here! ^_^

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Guest JBaymore

You have no idea how happy I am to FINALLY see another lowfirer here! ^_^

 

Hey... I low fire sometimes.  The cold part of the wood kiln is down at about cone 8-9.  ;)  :D

 

Seriously.. .... I do fow fire sometimes....... overglaze enamels at 015-017 and gold luster at 020.

 

best,

 

........................john

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Tyler,

No probblem picking out my post, I'm happy to have an inteeligent debate.

The reason lead hasn't been banned from dinnerware glazes is that if the glaze is well formed, there is no health hazard to the user.

The problem with lead glazes is the hoby/craft sector, most of whose practioners don't have access to the knowledge of glaze chemistry that industry does, who tinker with glaze recipes without fully understanding the issues in making a safe, well formed glaze.

I, and most other readers here, probably do eat our fruit salad out of lead glazed bowls, with no ill effects.

FYI, using a lead frit has no effect on the safety or otherwise of the final glaze, it only protects the potter from lead poisoning when making up and applying the glaze.

As for lead pipes, one has to be careful with statements like this - lead pipes are more likely to be found in older houses that haven't been refurbished (it was banned in Europe in 1970 for new builds), so the properties with lead pipe are more likely to be owned by poorer people, and poverty has been shown to be the biggest predictor of life satisfaction scores, so is it poverty or lead piping that is at fault?

Tim

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