Helter Smelter... flakes of lead in skillet

[Lewis Downey]

I purchased this Cast By Calphalon skillet not thinking much about the grunge in the bottom. After it was in the lye bath for a couple of days I pulled it out for a first scrub and a look-see.

The scrubber picked up bits of metal, including one large flake in particular. The skillet has been used to melt some kind of metal - I assume lead. The mottled texture on the bottom, which I took to be ordinary grunge, is actually melted metal.

I'll pitch it of course. At least it is neither a special nor expensive piece. It sat in a recycling pile for a couple of days after its condition was discovered. Some rust appeared during that time.

Am posting this so that others can see a skillet used to melt - probably a safe assumption - lead. I have had a one or two of other pieces that looked suspicious and were pitched. With this one, I am quite positive.

The pics:

lead_smelter_before_cleaning.jpg (before cleaning)
lead_smelter_mid_lye_bath.jpg (after a couple of days in the lye bath, notice the big flake of metal at the top.)
lead_smelter_close_up.jpg (close-up. There are bits of melted stuck around the edge. The bottom still looks mottled.)

[Lewis Downey]

Does anybody know if the lye bath will dissolve lead? I would hate to pitch the entire 55 gallon bath, but I will if there is a danger to other pieces that go through it.  It did not dissolve the lead on the skillet in any way that I can tell.

[Russell Ware]

I wouldn't be worried about lead in the lye. To dissolve lead you would need an acid environment.

[Jeff Friend]

There could be a significant amount of lead dissolved in your lye bath.  And remember, for lead, it does not take much to be a potential health issue.  The question you need to ask is this:  will there be enough lead that adheres to a skillet cleaned in the lye bath to affect someone's health?  It would take a lot of work to answer that question.  And since you should avoid having any exposure to lead, my advice is to start over.

For what it's worth, there are species of lead that are soluble at high pH values and species that do not dissolve at low pH (acidic) values.  A car battery is full of sulfuric acid, yet the lead plates don't dissolve.

[Lewis Downey]

Thanks Jeff,

What would cause dissolved lead in the lye bath to bond with a pan in such a way that a thorough cleaning would not remove it?

Would a 3M lead test on a couple of cleaned pieces that had been in the lye bath at the same time as the fouled pan be pointless?

Would the electro make any difference either way? Would it cause lead to bond with the iron pan? Would it remove or mitigate the lead in any way?

[Lewis Downey]

Best case, what should happen with the 10 pieces of iron that were in the LB with the fouled piece?  One of those pieces does not belong to me.

[Stephen Amaral]

FYI; pure lead begins to melt at 327* F. If there is tin or antimony in it, the melting point increases.
I have used a handheld propane torch with a "pencil" tip to test if a metal is lead or not. I prefer the 3M test.

[Lewis Downey]

Thank you Stephen. Also thanks to Russell for his insights the other day.

A friend pointed me to this article on plumbosolvency. It is encouraging and helped direct research into related articles.

https://en.wikipedia.org/wiki/Plumbosolvency

My current plan is to wander around the chemistry department of NC State with a sample of the lye bath, one the skillets that is in the LB, and a control skillet in hopes that someone from the department can either test the items or provide definitive opinions.

In order to do that I will have to summon the will to find parking near the university... that could take a few days.

[Lewis Downey]

I had the opportunity to meet separately with two professors from the chemistry department of NC State University this week.

Special thanks to Dr. Feducia and Dr. Martin for spontaneously and generously taking the time to talk to me.

There was good consensus of opinion between the two.

• The lye probably precipitated some lead off of the skillet. The precipitated lead would be in a form that is not going cause a problem. The lead would not be seeking an opportunity to bond with other metals.

• There are no forces in play which would cause the precipitated lead to alloy with iron in the pans.

• Any lead that happened to be on the surface of the pans from the lye bath should be removed by a thorough scrub before electrolysis.

• Dr. Feducia, an organic chemist, seemed a little less concerned about the lead and slightly more concerned about other things that might be in the lye bath after cleaning the 100+ pans that gone through it prior to the leaded skillet. He did not want to use the finished cookware. He recommended that I talk to Dr. Martin whose expertise is more relevant.

• Dr. Martin, an inorganic chemist, would use the finished cookware. He said that after a thorough soap and water scrub followed by electrolysis, he would treat the pans with citric acid before seasoning. I am going to do so. I asked about using acetic acid (vinegar) instead. He said that citric acid would be more able to combine with anything on the surface. I asked at what concentration. "Any reasonable concentration" was the response. I asked if a pound of citric acid in two or three gallons of water would be reasonable; the response was "yes". I asked soak or scrub... "both". At the end he suggested that if I could not find citric acid easily, scrubbing the pan with lemon juice and salt would be appropriate. (A quick search of Amazon shows that citric acid is readily available and inexpensive.)

• Both chemists recommended disposing of the lye bath. My perception is that this is in an "abundance of caution" recommendation, albeit one I am gong to follow.

---

I think I am going to make a practice of running any pan that is heavily textured on the inside through a separate small lye bath. If lead shows up, I'll only have to dispose of a small bath rather than a big one.

I think this should be mentioned... The comments from the chemists were about lead found on a skillet that went through the lye bath but did not go into the electro. The question of whether electrolysis would cause lead to alloy with iron or otherwise become a problem was hinted at but not discussed. If you go straight into the electro without using a lye bath, the comments above may not apply.

[Cheryl Watson]

Thank you Lewis!
What you are stating is consistent with my previous research.

I believe the lye bath would cause lead to convert to "lead plumbate?"....and another compound/substance.  (I didn't read your link yet, maybe soon.)

I also quarantine a lye bath for Painted pieces stripping... just as a precaution.  I also exercise the 'abundance' of caution practice, and will dump the lye bath before processing other cookware.

The citric acid recommendation is interesting, and new to me!.

[Claudia Killebrew]

I had the opportunity to meet separately with two professors from the chemistry department of NC State University this week.

Special thanks to Dr. Feducia and Dr. Martin for spontaneously and generously taking the time to talk to me.

There was good consensus of opinion between the two.

• The lye probably precipitated some lead off of the skillet. The precipitated lead would be in a form that is not going cause a problem. The lead would not be seeking an opportunity to bond with other metals.

• There are no forces in play which would cause the precipitated lead to alloy with iron in the pans.

• Any lead that happened to be on the surface of the pans from the lye bath should be removed by a thorough scrub before electrolysis.

• Dr. Feducia, an organic chemist, seemed a little less concerned about the lead and slightly more concerned about other things that might be in the lye bath after cleaning the 100+ pans that gone through it prior to the leaded skillet. He did not want to use the finished cookware. He recommended that I talk to Dr. Martin whose expertise is more relevant.

• Dr. Martin, an inorganic chemist, would use the finished cookware. He said that after a thorough soap and water scrub followed by electrolysis, he would treat the pans with citric acid before seasoning. I am going to do so. I asked about using acetic acid (vinegar) instead. He said that citric acid would be more able to combine with anything on the surface. I asked at what concentration. "Any reasonable concentration" was the response. I asked if a pound of citric acid in two or three gallons of water would be reasonable; the response was "yes". I asked soak or scrub... "both". At the end he suggested that if I could not find citric acid easily, scrubbing the pan with lemon juice and salt would be appropriate. (A quick search of Amazon shows that citric acid is readily available and inexpensive.)

• Both chemists recommended disposing of the lye bath. My perception is that this is in an "abundance of caution" recommendation, albeit one I am gong to follow.

---

I think I am going to make a practice of running any pan that is heavily textured on the inside through a separate small lye bath. If lead shows up, I'll only have to dispose of a small bath rather than a big one.

I think this should be mentioned... The comments from the chemists were about lead found on a skillet that went through the lye bath but did not go into the electro. The question of whether electrolysis would cause lead to alloy with iron or otherwise become a problem was hinted at but not discussed. If you go straight into the electro without using a lye bath, the comments above may not apply.

I find that bit interesting. I wonder what he feels could be left that would contaminate the pans?

[Lewis Downey]

Claudia,

If I get the vibe that he is open to follow-up questions, I'll ask for details.

It seemed like he was distrustful of chemical procedures undertaken by amateurs when lead and unknown other contaminants could be involved. He was concerned because he had not controlled the processes from start to end and did not know what else might be in the lye bath or electrolyte. 

[Jeff Friend]

A couple of questions and comments . . .

Lewis states that the professor indicated that "the lye probably precipitated some lead off of the skillet. The precipitated lead would be in a form that is not going cause a problem."  Is this intended to mean that the lye removed lead from the skillet?  Or, lead that came off the skillet and subsequently became a contaminant in the lye bath was precipitated by the lye?  There is a big difference.

Did the professors mention the term "amphoteric" during the discussion?  Lead that is dissolved in water can be removed by the addition of sodium hydroxide.  This precipitates the lead as lead hydroxide.  One might think that the addition of an excess of sodium hydroxide would make this reaction proceed faster or more completely, but it does not.  The compound that is formed with excess hydroxide is soluble in water.  Lead hydroxide is amphoteric, meaning that it can be dissolved in both acidic and strongly basic solutions.  There is a narrow pH range where lead hydroxide is insoluble.

Citric acid is a chelating agent.  When the professor said it would combine with things on the pan, he meant that citric acid (as well as oxalic acid and EDTA, the active ingredient in EvapoRust) can attach to metal molecules.  The use of citric acid in washing the pan is to have it chelate (attach to) the lead molecules, making them soluble in water and more easily removed from the surface of the pan.  Oxalic acid is the chelating agent in Bar Keepers Friend.

[Lewis Downey]

Lewis states that the professor indicated that "the lye probably precipitated some lead off of the skillet. The precipitated lead would be in a form that is not going cause a problem."  Is this intended to mean that the lye removed lead from the skillet?  Or, lead that came off the skillet and subsequently became a contaminant in the lye bath was precipitated by the lye?  There is a big difference.

Did the professors mention the term "amphoteric"

Hi Jeff,

They might have used any term at all and it would have gone right over my head fast enough to make an audible swooshing sound.

As you might have figured from the previous post, I dropped by for an unscheduled visit on an afternoon when they had office hours. In one case I sat in a waiting area while a student discussed course material the professor then stuck my head in the door afterwards and camped on a few minutes of his time. The other visit was similar but no students were ahead of me. They gave an experts' shoot-from-the-hip response as opposed to a critical laboratory based analysis tied to tests of the physical materials. I did my best to recount those responses.

The general vibe was that they were happy their insights were helpful, but the vibe was not that I should regard them as an regularly available resource. Perfectly understandable. I'll pursue more information from that department when it *feels* right to do so.  Between now and then I'll save a sample of the lye bath, the leaded skillet, and one of the other skillets that was in the lye bath. If any additional information comes to light I'll share it.

I can add just a little bit more from Dr. Feducia. Before leaving I wanted to confirm with him the gist of what he thought. I used the word "salt" in describing the lead in the lye. It had come up during the discussion. He quickly corrected me by saying that if the lead had formed a salt it would have been the scenario we did not want -- but such was not the case.

"Salt" is not an appropriate description of the lead in the lye bath, if that helps at all.