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I recently re-tinned an old copper pan with a good layer of tin. But after a few uses i am able to see the surface bubbling and forming boils making the surface rough.

I am not able to understand the issue, can somebody help me understand?

Vikram
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    I strongly suspect this has a lot more to do with metalworking than cooking. The surface prep is always my first thought when it comes to failing coatings, but even if we knew enough about metal plating on here, you haven't said what plating method you used. – Chris H Dec 22 '22 at 11:52
  • Chris, we used the traditional hand tinning method for utensils. – Vikram Dec 22 '22 at 12:15
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    but there's not just one method. Like I said before, surface prep is crucial. What processes/materials did you use? What flux did you use? I'm going to ask for this to be migrated to the crafts site as it's not about cooking, but it will need to more detail if it's to be answerable. – Chris H Dec 22 '22 at 12:19
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    Are you accustomed to cooking in tin-lined vessels? If not, you might just be melting the tin, it requires a very precise temperature management. But if you have cooked in this pan (or similar ones) for a long time without issues, then I would agree that this is not a problem of the cooking technique. I wouldn't make a strong judgement on whether it is on-topic for us (we do accept equipment maintenance questions, such as knife sharpening) but we have to see if answers come in. – rumtscho Dec 22 '22 at 12:36
  • @rumtscho good points - bubbling sounds more like poor adhesion than melting (which is why I suspected surface preparation and wondered about the flux) but I'm not an expert. – Chris H Dec 22 '22 at 12:38
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    But now I'm also wondering about the source and purity of the tin - pure tin melts cool enough, but common alloys ecen cooler – Chris H Dec 22 '22 at 12:50
  • Vikram: you might need to find a different SE that deals more with metalworking to get an answer. – FuzzyChef Dec 22 '22 at 18:17
  • I'm happy to migrate this to http://crafts.stackexchange.com/ - just let us know where you'd prefer to ask it, given the caveats people have noted above. – Cascabel Dec 22 '22 at 18:22
  • Although I had a quick chat with a Arts & Craft mod. Quote: „… that kind of metal work and maintenance doesn't have a big audience here. It's probably more likely to get an answer where it is.„ – Stephie Dec 22 '22 at 18:53
  • Yeah, what this question needs is really "Metalworking SE" or "Metallurgy SE" and I don't think either of those exist. Me, I retin my pots by taking them to the retinning shop. – FuzzyChef Dec 23 '22 at 06:56

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The symptom you describe suggests the problem is that the copper wasn't clean enough when you tinned it.

When the copper is properly tinned, you have a layer of copper, a layer of tin, and where they meet, there are molecular bonds between the metals that create a new compound that locks together the atomic lattices of the two metals. For that to happen, the two pure metals need to be in contact with each other with nothing between them. There can't be even a trace of oxidation or any kind of residue. The flux prepares the way for the bonding to take place between the pure metals.

Once it's properly tinned, if you overheat the pan, you can melt the tin layer, but that won't break the bond with the copper. If it isn't properly tinned, melting the tin can expose flaws in the process.

If the copper surface isn't perfectly clean everywhere, the tin can bond in the locations where it's clean, and bridge over small areas that aren't. If you overheat the pan and soften or remelt the tin, the impurities trapped under the bridged tin can affect the surface.

That's why the tinning process involves numerous steps to clean the surface down to pure metal.

fixer1234
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