Retinning Bi-metal Copperware and Clad
- kaleokahu Mar 26, 2012 04:06 PM
Today I learned a few things from a professional retinner. Among the most surprising things in a dayful of surprises was that one can "re"tin the modern bimetal copper pans lined in SS, as well as clad. Heretofore, I was under the misimpression that once salt or acid pitting ate through the SS lining, the pan was a goner. This is apparently not the case, and tin can be applied to rescue the pan. IMO, this removes a reason not to invest in Falk, Bourgeat, Mauviel or the other bimetal pans.
I will find out if tin may also be applied to line aluminum. If *that* is the case, discoloration of sulfurous foods and leaching aluminum will cease to be a reason to avoid that metal.
That's really interesting, and also explains why I received a copper frying pan on ebay with a tin lining which has worn through in areas to reveal its stainless steel original lining...
So let me pose this somewhat off-topic question:
I am a fan of tin-lined copper pans. However, I got to thinking that if the tin is being "worn through" necessitating re-tinning, that suggests over the course of the life of the pan:
1. tin is melting and getting in the food (and thereby inside my family members)
2. is melting and shifting around the pan and clumping to reveal the copper underneath, without necessarily getting into the food
3. is vaporizing (which I believe to be unlikely)
Is there any evidence this is unhealthy? I sure as heck hope not.
I'm no authority but my take is: (1) No, I don't think the tin is *melting* into the food. (2) I have one pan in which the tin does seem to melt at a lower temperature and *smear* a bit--this may be evidence of an impure alloy of tin (yes, perhaps a little lead!). Or, it could mean that the pan was not retinned properly and the latest layer of tin is not adhereig to a previous layer very well. (3) Tin oxidizes over time, which is why it darkens and ultimately looks powdery-grey. As long as there is no verdegris, it is safe.
The vast majority of tin loss is from abrasion with cooking and cleaning utensils. I think cooks of old were harder on their linings than we tend to be, babying them less, because a tinner was just around the corner and it wasn't a big hassle or $$ to do. Our friend the retinner says with *daily* use, a lining should last 5 years.
At one point I Googled "tin toxicity". While there is such a thing, my sense was it's about as big a concern as "water toxicity".
Wow....the thought of buying good, thick aluminum cookware and getting it tin lined is really intriguing! I want to learn how to re-tin a pan and I am comfortable working with metals and such because when I was a general dentist before I specialized into surgery, I loved casting and buffing and polishing and all the lab work.
Have you tried tin lining an aluminum pot, Kaleo?
Julia Child said it was safe to cook in pans with exposed copper as long as they're scrubbed out before using. Do you leave verdigris in your pans just to remind yourself how they look?
Of course the trace numbers of other elements in refined tin can vary batch to batch. But even if you refine it yourself by skimming, it is 99.5 pure--the way it's been since I think 600AD. Commercially refined tin is usually 99.85% pure. So, yes, the lead content might vary--in the range of 0.002-0.008%.
Quite the Gotcha. Keep up the good work.