Can't lead just be wash off?

[LaybackPandas]

say you brought a plate which happens to have lead on it, if you wash it with soup wouldn't that take care of the problem?

[bsteele]

What kind of soup is best to wash with? Tomato?

In other news... I'm 99% sure the lead cannot be washed off-- it's in the ceramic or... glaze... or something.

I wonder if you could put a new lead-free glaze on the plate. Just make sure the new glaze doesn't chip off

Oh and if you experience any of the following... I'd see a doc
* Abdominal pain and cramping
* Aggressive behavior
* Anemia
* Constipation
* Difficulty sleeping
* Headaches
* Irritability
* Loss of previous developmental skills (in young children)
* Low appetite and energy
* Reduced sensations

[Maitre_Tea]

if you could wash it off, there wouldn't be the ongoing discussion about food-safe raku

[bsteele]

The Raku Food Safety discussion: linky link link

[GreenwoodStudio]

Hi Layedback-

Without getting too technical, the short answer is no. There's not a seafood bisque nor tomato soup in the world that would wash off the lead

I'm just kidding, I'm pretty sure you meant soap But the answer is still no. Lead is used as a flux (melter) as part of the composition of some glazes. It can be broken down by acids in foods or drink and absorbed into the body.

[betta]

say you brought a plate which happens to have lead on it, if you wash it with soup wouldn't that take care of the problem?

I believe you meant here soap. The answer is no, but I know one liquid which might help to remove lead: Aqua Regia

[JBaymore]

laybackp,

One of the subjects that I have been teaching at the college level for a LONG time at the undergrad and grad levels in art schools is ceramic toxicology.

Nothing is going to "wash off" the lead. As greenwood mentioned, it is typically lightly bound into the glass matrix (acting as a flux on silica)... and is contained throughout the 3-dimensional glass layer.

The lead leaching subject is VERY complex. There are a lot of variables involved so there is no "blanket" answer. In some cases lead release decreases with subsequent leaching tests (these use a material similar to vinegar), but in some cases it actually gets worse. This is sort of counter-intuitive. You'd think that as you leached some out...... the amount released later would decrease. Not always the case.

Some lead containing glazes are formulated and fired in such a manner that they will pass the US FDA lead release standards for tablewares. (Different forms of tableware have different lead release values with which they must comply.) But the California standards are tighter than the USFDA ones..... and few to none will pass those standards.

Fire those glazes just a tad wrong.... and they then don't pass the leaching tests. Change the thickness of application... and the lead release can go up. Lots of variables.

If you know you have lead glazed stuff........ you likely just want to "admire it from afar" unless you are a "risk taker" personality type. The issue of lead toxicology in the human body gets into intensity, duration, and frequency of exposure issues among other things, combined with genetic pre-disposition, and total body burden of other toxins that might also offer some synergistic effects. There is no one "right" answer for every situation; they are case-by-case studies. And if you aren't able to do that study....... then you need to make an educated guess as to how careful you should be. We're back to assessing that "risk taker" personality type.

I can give you the address for testing labs that will test your ware for you. It will then give you concrete numbers that can be compared to the USFDA lead leaching standrads for tablewares. It is minimally destructive testing; in most cases you will see no visible change in the ware tested. It'll cost you about $60 plus postage to test for a single metal release (like for Pb). Add about $30 per every other element you want to test for.

If you want to get into some really interesting ceramic toxicology stuff........ look at early Fiestaware. The red/oranage stuff contains not only a nice bit of lead.... but radioactive thorium contaminants in the glaze as a part of the colorant content! So if all you have to worry about is the lead.... you are in good shape.

best,

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

PS: I'm guessing hot and sour soup might be the best type to use .

[Geekgirl]

Interesting you mention early fiestaware. A huge portion of vintage FW in the orange/red ranges color shift dramatically over time, suggesting degradation of the glaze. I was not aware of the toxicity issue, but as a longtime "fan" of HL, particularly FW, I do know that it is recommended to buy modern versions of certain colors if you desire to use them for normal everyday usage.

[JBaymore]

Geekgirl,

A collection of early red/orange Fiestaware will nicely light up a Geiger counter.

As to color shift.....

Yeah.... degradation of the glass matrix. Well known. Look for a VERY thin layer of white dust forming on the surface when in long term storage...... that is white lead oxide forming as lead from the glaze combines with atmospheric oxygen. I have a friend who has studied this.

Color degradation actually happens with many glazes.... the issue is that it is so slow that most people do not notice it. (Plus your color eye is good compared to most people's .) A lot of the glazes on pieces that we see in museum cases look a bit different than they did "in their own time".

Everyone seems to just assume that ceramic glazes are somehow totally inert and 100% "stable". This is not technically true. Some glazes are far, far more stable than others. While not technically true, the difference is so slight that for the most part you can think of most glazes as fully stable for practical purposes. (Look at pieces like say, Sung Dynasty work ....... while the glazes may have changed a tad .... they are still pretty intact glassy layers on the pieces after all this time.) For about 99.99999999 % of glazes this leaching possibility is not an issue, because they are stable enough in the context in which they are used that the slow degradation is not offereing any real risk. And most glazes contain little in the way of materials that are of concern in the leaching department.

Firing range is not an absolute guarantee of stability, although as a broad generality (due to the chemistry differences) high fire is typically more stable. There is a popular "high fire" copper green glaze in regular studio use in the USA amongst "art potters" that is a variation of a Japanese glaze usually called "Oribe". There is at least one version of this recipe circulating that releases copper quite nicely. If you put a sample of that in vinegar overnight or place a lemon slice upon the surface for a few hours...... you'll see a clear color change in the area treated. While copper is not all that toxic to most people (there are certain people with a disease that makes them have far more of an issue with copper).... it does affect taste in even low releases situations.

Glaze/ glass stability is a very complex subject with lots of variables that can affect the outcome.

best,

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

[GreenwoodStudio]

Thanks for your thoughtful posts John!