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Pumice for annealing

Hi,

Regarding pumice, I was wondering if/ why pumice is best for annealing sterling silver and brass?

From my quick searching, I “think” pumice is heat refractory/ resistant? Meaning that it does not soak up heat/ take heat away from the piece being annealed?
(low thermal conductivity…?)

Is pumice also heat reflective?

I “think” Solderite boards are heat reflective…?

I am confused about refractory versus reflective…

Would pumice be the best choice for annealing sterling silver and brass?

Any thoughts would be greatly appreciated.

Best Regards,
Julie

As a silversmith, I have annealed a great many pieces (mostly large) of silver, silver copper alloys, copper, and copper alloys.
Pumice is very convenient on a rotating hearth because you can arrange the granules to form a nest to approximate the shape of your form, which might help avoid ‘hot spots’. Usually (not always) one wants to heat evenly all over.
Flat soldering surfaces are usually a pain because you then have a large mass of red-hot metal, potentially unstable if rounded or irregular. And if the metal item has a flat base, the heat of the torch won’t easily get underneath it.
I also occasionally use ceramic fibre (“wool”) as a bed for metal items since it can be formed to make a better nest, and help achieve an even heat all over.

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I just heat up whatever I am annealing on a solderite board until it is ready and then quench it. This is true regardless of size and shape. Pieces can vary from 30 grams of 8 gauge twisted wire to .5 grams of filigree wire. I have had my “Oh Sh*t” moments, but I think that they are a result of my being inattentive to what I am doing and not the surface on which I am annealing. The surface on which I solder is another story. I especially like charcoal. I usually anneal with an EZ Torch as the flame is gentler and more easily controlled than a gas and O2 flame. I have also recently equipped my old burn out oven with a new digital controller and will use it to anneal and heat harden large amounts of sterling silver wire…Rob

I annealed, heated, and soldered on hard firebrick and have for about 25 years. I recently started using solderite and charcoal for soldering at my brothers suggestion. There is a learning curve to that but I am rounding the bend . I still anneal on the hard firebrick.

Yes the hard brick is a heat sink and it takes away the heat quickly. But it isn’t a matter of whats the best or worse product; Its a matter of what works best for the user. This is what I learned on. I bought hard brick because I could find it locally and I didn’t have to wait for what ever Rio had to ship it C.O.D. over UPS. Like Rob I have had a few pieces burn up. My guess is everyone has. I anneal in the dark and rely on my sense of color before I quench the product in the pickle.

Maybe some time I’ll try pumice but I haven’t found a compelling reason to for the jewelry I am producing at the moment.

Don Meixner

Hi!
Thank you all for your comments!

Julie

Pumice is nice for annealing a steel part because when you’ve finished heating it to red you can bury it in the pumice, which insulates it as it cools slowly.

But silver and gold anneal differently - with them, you heat the part to red, then quench it immediately. This would harden a steel part, but it works the opposite way in precious metals. You can still use pumice as a bed liner for your soldering pan, but a soft firebrick works just as well for me.

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Hi, when I first learned to solder a very long time ago. Pumice stone was large - .5” to 1 inch. How come this is not available? I don’t like using the small granules. I purchased pumice stone for plants and this did not work at all… it was funny- sparks started to fly.
Does anyone know where I can purchase this type of product.