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NDclaypots

Help With Substitute For Lead Bisilicate

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NDclaypots    0

I am a ceramist for over 20 years and am desiring to do lustreware not based on the commercial jars of paint but actual fuming with the silver and copper and have Greg Daly's book on lustreware and only starting reading it and lots of info and line blends etc. but the process appears to make use of lead basciliate which i am not sure I want to get into?  I have both electric and gas kiln.  Any helps or directions of how to proceed would be helpful. I am thinking we do not yet have a sub for lead though? I am sure their are more knowledgeable people on this subject. Thank you.  Looking forward to hearing from you.

 

Llewellyn

Abbey Pottery

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JBaymore    1,432

Welcome to the forum.

 

Make sure to read up in detail on the appropriate handling of lead materials before you get too far into this.  To handle them safely in the studio is not impossible but difficult. 

 

Lead is one of the great fluxes...... except for this one little itty bitty issue,..........

 

There is nothing that is a direct sub for lead bisilicate.  Bismuth and boron are the usual suspects to start investigating.

 

best,

 

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

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NDclaypots    0

Thank You John for the welcoming.  I appreciate very much the advise you give and will be well headed.  I'm going to get some clay test tiles made up and begin the process of discovery and mixing up some base glazes and responses to that, just a few to start with- maybe two.  Greg Daly's book is packed with information for a start.  Are their any specific chat lines or other places that I should know about on the internet out there that I might benefit from study group, questions, input etc. related to Lustre firing.  I just unloaded an electric kiln of bisque (porcelain) but need to build up enough to fill the gas kiln - 100 some pieces then I'll be ready to glaze and that'll also give me some time to catch up with the process of getting some test tiles readied.   Thanks much.   

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JBaymore    1,432

There is not a lot of interest in this technique in the western world.  Quite specialized.  So I don't know a lot about it other than concept. 

 

Some general luster reference (Johanna frequents this forum):

 

http://johanna.demaine.org/blog/wp-content/uploads/2013/03/Lustre-Ceramics-Monthly.pdf

 

 

Someone doing traditional luster ware:

 

http://haggertyceramics.com/Web%20Pages/Ceramics%20Monthly%20Article.htm

 

 

CLAYART list discussion:

 

http://www.potters.org/subject22591.htm

 

 

best,

 

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

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NDclaypots    0

Thank you John for the forum lists and clay artists. I checked out Johanna's work and is all beautiful work.

I have some test tiles drying and will begin the long process of discovery. 

Best Wishes,

Llewellyn

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Tim T    46

Sutton Taylor's work is wonderful, IMHO. See http://www.oxfordceramics.com/sutton-taylor-1

There are also a few people doing lustreware in the UK following on from William de Morgan's work.

If you are not doing pieces for food or drink, lead bisilicate isn't much of an issue as it is a frit that has the lead in an almost insoluble form, though you do need to be a lot more careful if using red or white lead, and lead sesquisilicate isn't as insoluble as the bisilicate.

If you look into the chemistry of lead, there is a lot more to it than just the low MP and high refractive index, the chemistry with the silica and the colourants is fundamentally different, so other materials are more alternatives than replacements.

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Tim T    46

An MSDS data sheet is a good starting point but doesn't really give the full story, it just highlights the risks for high levels of exposure to the substance. There are many other things to consider:

 

For working with glazes in the UK you must either use a lead free or a low solubility lead glaze, where low solubility measures the amount of lead released from mixing the dry glaze in hydrochloric acid. Lead bisilicate releases little lead in this test, so any lead glaze using lead bisilicate can be used.

 

You must ask yourself how much exposure you have to the material. In the UK when looking at long term effects (as is the case with lead) if you are working with it all the time then this is averaged over an 8 hour period (ie a day), or if you work with it intermittently then this is averaged over a 40 hor period (ie a week). So if you are mixing lead glazes for 1 day a week then the exposure can be 5 times higher on that day than if you do it every day.

 

Then you need to look at how the toxic material can get into the body. Lead bisilicate isn't absorbed through the skin, and if ingested through the mouth in the quantities likely in a studio using good practice (i.e. no food or drink, no licking of brushes for applying glaze, washing hands/using gloves afterwards etc) is not going to release a significant amount of lead passing through the system, so the main risk is airborne inhalation.

 

If you look at the HSE airborne limits for lead in the UK, this is 0.15mg/cu.m of lead (corresponding to 0.37mg/cu.m. of lead bisilicate), which is higher than the limits for chromates, nickel, cobalt and vanadium. The question is, how much of the lead in your glaze will get into the air - primarily by using dry materials when mixing the glaze or doing things like scraffito, or by over firing the glaze so it gives off lead fumes in the kiln. And then, how much will be filtered out by your dust mask? This can only be ascertained by measurement, which is beyond the skills or cost effectiveness of studio potters, but guidance from the HSE is in these document:

http://www.hse.gov.uk/pubns/priced/l60.pdf

http://www.hse.gov.uk/pUbns/priced/eh40.pdf

http://www.hse.gov.uk/pubns/priced/l132.pdf

 

Also this is a very useful reference on lead glazes not just in manufacturing, but also on tableware:

www.ilmc.org/Publications/ILMCFinalCombo8-02B.pdf

 

Yes, lead presents hazards, but if used intelligently they are perfecty manageable, the same as with many other potter's materials. And it is your choice whether to use it or not.

Tim

 

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JBaymore    1,432

Yes, lead presents hazards, but if used intelligently they are perfecty manageable, the same as with many other potter's materials. And it is your choice whether to use it or not.

 

The potential issue with studio ceramics in this subject area is that many folks have not been given much accurate information about the subject of toxicology (or even glaze chemistry), and many also do not grasp the science and math concepts behind things like ppm, the impacts of significant figures, what orders of magnitude might mean to exposures, and the like.  This is one of the reasons that I teach ceramic toxicology as part of required technical courses in our undergrad program.  Everyone graduating with those BFA letters after their name gets at least an attempt to communicate some accurate information.  It is a start.

 

There is TONS of what amounts to 'hysteria' that surrounds the topic of health and safety in the studio.  Lead, manganese, barium, and copper seem to get the most 'high profile' hysteria.  Interestingly, the issues with respirable micro-crystalline silica seem to get a bit underplayed.

 

Another REAL potential issue with online forums is that a VERY wide range of experience level people read the postings.  So what is "good information" for some people reading it who might have the appropriate education and context... can actually be "dangerous information" to the less experienced.  And because those folks are "unknowns" as far as what their educational path is or has been...... you never know if they are going to get that important information that is "left out" in the thread they have read. 

 

Some read "Just spray XXXXXXX on the work and you'll get XXXXXXXXXX"........ and run off and do it with no further research as to what they are working with.  The "assumption" tends to be that it is art... so it is OK.

 

Yes, SOME people can work with lead in the studio safely.  And you CAN have fired lead glazed work that is perfectly safe for the consumer.  To do either....... takes some serious and accurate understanding of what the potential issues are and how to correctly solve them. 

 

best,

 

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

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JBaymore    1,432

Moderation Note:  I am correcting the typo on the thread title line to "Bisilicate".

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Tim T    46

John, well done for trying to teach people the basics of this sort of stuff. Unlike many potters I'm from an engineering background and so am familiar with much of these ideas, but you talk to many potters of all levels, from beginners to professionals, and it is totally outside their area of understanding, so either they stick their head in the silica and say it'll never happen to me, or get over excited about whatever the latest scare story is.

One of the HSE links (I forget which) is guidance for potters, and is clearly and well written on the risks and on good studio practice for non technical people.

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