Re-tinning copper cookware has been a very eye-opening experience for me in terms of understanding copper on a very physical level, that has everything to do with something I cannot control, and nothing to do with how the copper pot actually performs for cooking.
There are certain grades of copper that take the tin really well. It wipes on like butter and stays smooth and shiny. It can look like clear moonlight captured inside a pan. It’s utterly gorgeous. The man who taught me, Dan, is a god when it comes to tin lining copper, and he’s been a mentor from afar for me whenever I hit a snag, have a problem, or get in a rut. He’s even done videos using a plastic tray, a rag, and soap to explain how to properly wipe out a big pan and gone over some of my issues with me via Facebook, text, and phone. I owe him so much of this piece of my trade, and I’ll be grateful forever.
But I digress. Copper grades. That’s what we’re discussing.
Anyway. Pure copper is the best in terms of conductivity because even though it’s quite soft, it doesn’t have any other elemental molecules to keep the heat from transferring well. But there are even different grades of the copper. When I first started designing copper cookware, we planned on using CDA110, which is pure. But it didn’t hold the tin well, and Dan found it took sometimes 2-3 passes through to make the tin look smooth. The tin kept beading off. And one pan I do have from somewhere else that used the 110 did indeed have the tin pop off, leaving a darker oxidized tin in places. Tin shouldn’t chip off like that. It can, of course, if abused, but I know how to cook in tin-lined copper and that type of separation is not usual or ideal.
We found out pure copper that is de-oxidized with phosphorous during the smelting/rolling phase holds tin better, and allowed for a quicker finish. It made tinning the House Copper pieces so much easier.
Which brings me to my next point. Vintage copper is a bit of a gamble. I never know the grade, and usually copper cookware made in the old days wasn’t as pure because they didn’t have the technology to not only infuse the copper with phosphorous, but also they didn’t have a way to make copper as pure in general. I also have to battle grime and dirt from decades of use and abuse. Tin doesn’t adhere to oxidized tin, nor to dirt. It’s a very long process, with multiple acid baths, sanders, grinders, and bead blasters to get an old piece ready to take new tin (hopefully).
Once we get over the fire, the copper grade really shows its colors. Sometimes the tin wipes on beautifully. Sometimes I can go over the fire 4 times and still be completely dissatisfied. Sometimes I have to scrub with a wire brush or rub really hard to get the tin to take. Add in humidity, wind, the weather in general, and there’s always something else to be cognizant of when going into the tinning process.
Basically, every single time I go over the fire, it’s a challenge. There’s never much of a guarantee that it will work out well, so there’s always a deep breath, a bit of a prayer to the copper gods, and then diving in. It’s easy to get caught up in the fear, and it sometimes takes a few days for me to psych myself up to do a batch.
It’s a good thing my motto is: “Why not? Just dive in and DO it!” otherwise I’d never tackle tinning a single piece of copper.