Does breaching a stovetop milk steamer's double wall destroy it?

Question

I have a stovetop milk steamer & espresso maker whose handle fell off. The spot weld failed after a few years of use.

Using a TIG welder, I welded the handle's thread back to the lid.

Unfortunately, during the welding process I breached the double wall of the lid; a hole formed through which you could see the inside of the double wall. I filled in the hole and continued the weld as you can see from the photograph above.

My question is this: can I put this steamer back into service or is it a writeoff?

To know the answer to that question I think I need to know what the nature of that void was before I breached the wall of the container?

• Was it a vacuum?
• Was it filled with a special gas?
• Was it just plain old air?

If it was anything other than plain old air it's now filled with plain old air and a little bit of argon. All I really want to know is that it's not going to explode if I put it back into service.

Answer 1

The double wall on this steamer is not there for insulation. That idea doesn't add up. An exterior wall will heat up before an interior wall if heated on a stovetop and would inhibit transfer of heat to the interior container...

I can think of two possible reasons for the double wall, but I must say, that double wall is an unnecessary added expense on the unit no matter the reason it was included...

1) In a double wall design, the exterior wall will cool down faster than a single wall would, since the exterior wall does not maintain contact with hot water. This means you can safely reuse the steamer sooner. This is kind of silly, though, since you can easily cool a single walled steamer by briefly running it under cold water.

2) A double walled steamer is more structurally durable than a single walled steamer. These units are sometimes built to withstand very significant internal pressure. The double wall could be part of such a design. This is kind of silly itself because steam pressure higher than a single walled unit could support is dangerous...

The exterior wall in any case likely does not play any part in containing steam. To be sure, I'd need to see the inside of the lid. It depends whether the seal is placed on the outside threads or the inner vessel and whether a gasket is used or not.

Answer 2

My guess would be that was filled with air. As far as I can see, the double wall is there just to insulate, so you won't burn your finger when you accidentally touch it and for the coffee to stay hot.

That said, I would submerge it in a bowl of water and take it out after a minute to check that there are no holes.

If there are any holes, you probably want to clean it and make sure it's dry (dry it in the oven at a low temperature, 50°C (122°F) should be enough to help any water evaporate without damaging components). Then close the hole (with some of your welding technique?) and test it again. The reason you don't want a hole is that it's harder to keep clean and can be a nice spot for bacteria or other nasty stuff to settle.