Lead in Glass

[JetAge Studio]

That is really interesting Steph!! Thanks so much for your input!! Very cool to hear the medical world asks questions related to glasswork!! I'm surprised! (guess they're paying attention..) Good Doctor!! Thanks so much for your comment, it gives a lot of perspective!! (but now I wonder what the doc knows about lampwork!! )
Renee Wiggins

[Dennis Brady]

Originally Posted by JetAge Studio

That is really interesting Steph!! Thanks so much for your input!! Very cool to hear the medical world asks questions related to glasswork!! I'm surprised! (guess they're paying attention..) Good Doctor!! Thanks so much for your comment, it gives a lot of perspective!! (but now I wonder what the doc knows about lampwork!! )
Renee Wiggins

Suggests that the concern about lead poisoning from torching glass is about the same as the concern about it from using it for stained glass.

If you don't eat it you'll be fine.
If you're fool enough to eat it, lead poisioning is the least of your problems.

[ewdb]

when i told my dr i work with hot glass, he added a lead test to my annual physical.

does anyone else do this?

[Steph'sBeadCorner]

Originally Posted by ewdb

when i told my dr i work with hot glass, he added a lead test to my annual physical.

does anyone else do this?

Well... I think it's safe to say that if you're using basic glass that most lampworkers use... a yearly test isn't really necessary.

Of course, if you're more comfortable with a test, then go for it!

I would ask myself, do I want to pay for a test I didn't really need? I see you live in Canada, so that may not even by an issue.

And 2ndly, do I have adequate ventilation?? Since most of the problems with emissions are resolved by installing proper ventilation.

[Dennis Brady]

Originally Posted by Steph'sBeadCorner

Well... I think it's safe to say that if you're using basic glass that most lampworkers use... a yearly test isn't really necessary.

Of course, if you're more comfortable with a test, then go for it!

I would ask myself, do I want to pay for a test I didn't really need? I see you live in Canada, so that may not even by an issue.

And 2ndly, do I have adequate ventilation?? Since most of the problems with emissions are resolved by installing proper ventilation.

In Canada, the blood test is free but bloods test are notoriously inaccurate. To actually measure lead contamination requires a hair analysis test. That isn't normally free but if you tell your doctor you regulary work with lead, he can prescribe a free test. I started getting tested more then 20 years ago and stopped after about 10 years. Although I was steadily increasing the amount and frequency of lead I worked with, my lead levels were steadily decreasing. One possible explanation was simple. I had moved from a city to a small rural island where I wasn't inhaling the usual variety of vehicle and industry generated fumes. The other possible explanation was I had done nothing that would cause me to ingest lead. I don't know what lead tastes like and have no desire to find out.

[castaway]

Boy, there is a lot of miss-information out there isn't there, Lead is in glass to obtain certain colors, the lead increases the amount of the colorant( metal) that can be absorbed. Cadmium-sulphide reds do not contain lead, they contain Zinc
gold colors do contain lead as do the very dark copper greens. Lead will volatilize out of the glass at 999°C well below the temperature of your flame, the Gaffer test you will notice kept below this temperature. The difference between hard glass and soft glass is it's melting temperature or viscosity which controls the coe and thus annealing temperatures, Soda Lime glass is window glass and container glass it is not the glass that you are working with, you would not be able to work with soda lime glass it is very stiff and devitrifies easily, Boro also contains some soda( 4.5%). the colors in glass cannot be obtained in soda glass you need potash as the major alkali to produce most of the colors that you use, Nickle for example gives the lovely violet colors in potash glass but only a dirty brown in soda glass, the same for manganese, purple in potash and brown in soda. I think Emiko is correct here about the lead in Satake it is well over 30% by weight and is in the glass both to obtain the colors and to make it melt more easily and will come out of the glass into the atmosphere of your studio.
cheers, Bernard

[squid]

Originally Posted by castaway

Boy, there is a lot of miss-information out there isn't there, Lead is in glass to obtain certain colors, the lead increases the amount of the colorant( metal) that can be absorbed. Cadmium-sulphide reds do not contain lead, they contain Zinc
gold colors do contain lead as do the very dark copper greens. Lead will volatilize out of the glass at 999°C well below the temperature of your flame, the Gaffer test you will notice kept below this temperature. The difference between hard glass and soft glass is it's melting temperature or viscosity which controls the coe and thus annealing temperatures, Soda Lime glass is window glass and container glass it is not the glass that you are working with, you would not be able to work with soda lime glass it is very stiff and devitrifies easily, Boro also contains some soda( 4.5%). the colors in glass cannot be obtained in soda glass you need potash as the major alkali to produce most of the colors that you use, Nickle for example gives the lovely violet colors in potash glass but only a dirty brown in soda glass, the same for manganese, purple in potash and brown in soda. I think Emiko is correct here about the lead in Satake it is well over 30% by weight and is in the glass both to obtain the colors and to make it melt more easily and will come out of the glass into the atmosphere of your studio.
cheers, Bernard

I don't understand the part that I bolded above. We ARE working with soda lime glass.

[castaway]

not so dear you are working with a potash- lime glass, there will also be a small percentage of soda in the glass but the main alkali will be potash

[squid]

According to everything I have been able to find Potash-lime glass is Bohemian glass, container glass. Venetian glass is soda lime.

[LyndaJ]

So, potassium instead of sodium as the metal?

[squid]

Chemistry textbook

http://books.google.com/books?id=gu7...m=10&ct=result

Says that potash-lime glass fuses at a very high temperature and that soda lime is readily fusible.

[castaway]

Well, for a start glass is not "fused" to make it but disolved, a glass recipe for 'soft glass' would contain silica as the main glass former, and then an alkali, iether sodium or potassium or both, then stabalisers, usualy calcium, magnesium and other RO elements, modifiers, boron, barium, zinc, lead to name a few.
when glass "batch" is loaded into a furnace the lower melting materials begin to melt, things like sodium carbonate, potassium carbonate , the nitrates and borax all start to melt early, these in turn help to dissolve the RO compounds the resultant soup of "fluxes" dissolves the Silica Dioxide ( sand) Most glass of the "soft type is batched at between 1200°C and 1300°C regardless of their composition, the extra heat to make potash glass in not an issue for studio glass
as it is only a couple of hundred degrees( silica needs 2000°C to "fuse")
You will find very little on the composition of 'colored' glass, almost all the information you will find will refer to the "base glass" which is the clear glass which makes up the body of the piece. Almost all colors used in the glass blowing industry are lead colours, lead glass uses Potash as its flux although Kugler is now making a lead free range of glass colors using things like Barium and Lithium.
the ancient glass of northern Europe was "forrest glass' or "potash glass" they had no trouble making it in wood fired furnaces, and it was only when the forrests were gone that soda became an important glass flux.
it is true that 95% of all glass made is "soda lime glass" it is however window and container glass, art glass colors are not mentioned in many publications.
cheers, Bernard
It is still not possible to obtain the colors we are all using in "soda lime glass"

[JetAge Studio]

Originally Posted by castaway

not so dear you are working with a potash- lime glass, there will also be a small percentage of soda in the glass but the main alkali will be potash

I'm not quite clear about this statement either. I too am of the understanding that the glass we (soft glass) lampworkers use is Soda Lime Glass... Soda is a flux as well as potash, and a bit more of an efficient flux as I understand, therefore is used more readily (I'm guessing here) I think it's just generally understood that "soft glass" is Soda Lime Silica glass. Perhaps it's a "generalized" term. I'm no chemist, but I do have a passion for glass, so I'm naturally curious about this.

Here's what I know from my library;

I understand the definition of Soda Lime Silica glass as this:
the glass "former" is SiO2 (silica), with "modifiers" of;
(Soda) Na2O (from soda ash and/or nitrate) is the most important alkali for glass making.

(Lime) CaO (from Limestone). The most important alkaline earth for glass making.

Approx. 22% Na2O, 5% CaO, 73% SiO2 by weight IS Soda Lime Silica Glass according to my reference.

A host of other modifiers are secondary;
Potassia, K2O (from potash and/or potassium nitrate) "has a larger ionic size, and is less mobile, and therefore better for electrical insulation properties, but not quite as good a flux as soda." is one.

You're not possibly referring to "Lead Silicate" glass, which has a higher potash content as well as lead content (flint glass)? Which is also used as "container" glass? Just throwing that out there.

I'm also not quite understanding what you mean in this quote; "it is true that 95% of all glass made is "soda lime glass" it is however window and container glass, art glass colors are not mentioned in many publications.
It is still not possible to obtain the colors we are all using in "soda lime glass"

This could also be a very interesting discussion, but I'm not sure what you're referring to when you mention color...care to elaborate?

Very interesting. I'm just a little confused by some of your reference, or perhaps wording, but I'm in no way claiming I know better!
Thanks for the input!

Renee Wiggins

[castaway]

OK I will have a go Renee. I am not an industrial chemist, I am a glass maker of 30 years experience, glass chemistry was my area of study during my glass course. I have taught glass chemistry to art students at University( a very basic course, you can imagine)
Tere are three basic groups of chemicals in glass making,

glass formers: silica and boron are the major ones

fluxes: Na2O and K2O are the major ones

stabilisers: CaO and MgO are the most important

these are the glass formers

the other group of chemicals in glass are the modifiers, these modify the characteristics of the glass( melting temp, working time hardness etc.)
these are things like lead( which can also be a glass former( tricky isn't it)
barium, zinc,arsenic, antimony and lithium are some of them

the glass that you quoted:
73% SiO2 , 22%Na2O, 5%CaO is indeed a basic soda lime glass, however it would be very difficult to work with such a glass, believe me.

the "95% of all glass made is soda lime glass" is a reference to the much quoted figure used to show why most glass is 'soda lime glass' this is true but it does not refer to the glass that we use in lampworking, this is for the most part 'colored glass' the recipes for producing colored glass are nothing like the "soda lime glass" formula you have quoted.
the colorants in glass are for the most part metals, iether as atomic metal or as oxides or sulphides, these metals give different colors depending on the composition of the base glass, a real give away is a violet glass, this will be Nickle and must be in a potash glass to produce this color, in a soda glass it will be brown, there is no other way to produce a violet glass
there are many different "base glasses" used to produce the range of colors we use in lampworking, to simply call them "soda lime glass" is wrong and missleading a more corect term is of course "soft glass"
It is difficult to get information on the recipes for glass as each maker keeps them secret, the Italians are no different and to ask them what is in their glass is useless as they will tell you what they think you want to hear, or just limply say"Oh it's soda lime glass" and perhaps some of the glass they make is, but not the colored glass that we use.
cheers, Bernard

[RSimmons]

If you look at the X-ray spectra generated by many Effetre and other Italian glasses you'll see the markers for 'soda lime' flux agents along with a number of metals used for color generation.

Robert

[PittsGlass]

Originally Posted by RSimmons

If you look at the X-ray spectra generated by many Effete and other Italian glasses you'll see the markers for 'soda lime' flux agents along with a number of metals used for color generation.

Robert

Where can one see this?

This whole thread is just fascinating. I am anxiously awaiting more discussion. Thank you all for sharing your knowledge!

[RSimmons]

I'll post some data on this tomorrow.

R

[RSimmons]

I reviewed the X-ray data on a couple of the Italian 104 glasses (Vetrofond, Effetre). These include: EDP, a light ivory, an opaque yellow, a medium blue, a pink, white, a transparent green and an alabastro. Soda-lime is made up of calcium hydroxide, sodium hydroxide and potassium hydroxide, plus water in the raw form. The spectra from all of these glasses indicate the presence of all three elements in varying proportions. There are other metals that are commonly used as colorants for glass, but I don’t want to get into trying to publish formulas. I think that, based on the presence known flux agents, these can be considered soda-lime glasses.

Robert

[Lisi]

Oops, posted in wrong thread, but I'm glad I brought it up again! I had posted in the Bathroom about a potential customer that had asked me if there is lead in my beads.