Annealing Electroplated Silver for Daguerreotypes: Temperature & Flux Guide

Question
QUESTION: Hi, I work with an old photographic process -- the daguerreotype which uses electroplated silver on a copper substrate. The silver is about 12-25 microns; the copper is 0.020 inch. I would like to anneal the silver to increase its grain size and soften it. I have a thermostatically controlled lab hotplate and surface thermometers one of which goes up 1000 deg F. What annealing temp should the hotplate be set at?  And what flux should I use to prevent oxidation of the silver? Since the electroplated silver is
fine silver (no copper) should I be concerned about firescale?  Thank you. Irv

ANSWER: Hi Irving,
Set it to 900 deg F. and use the boric acid/denatured alcohol mix to prevent firescale.

Hope it helps,

Orlando Cajamarca

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QUESTION: Thank you Orlando for your extra prompt reply. Can Isopropyl alcohol be used w/boric acid? It is 75% isopropyl; 25% water.
Make a paste of the two?  How long to anneal at 900 degree F?
Again, thank you very much.

Irving

ANSWER: Hello Irving,
Sorry for the delay on my answer, using that kind of alcohol is mnot a problem. Do not make a paste, use 10/4 meaning 10 spoons of waref and 4 spoons of boric acid. It will give you a mix that is liquid enough and heavy enough to protect your piece of jewelry.
keep the item in the kiln at 900 degrees for 5/10 minutes.

Hope it helps,

Orlando Cajamarca
www.ocjdesigns.com

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QUESTION: Thank you very much for your answer. Can  you get different degrees of annealing by heating for a period shorter than the 5-10 minutes at 900 deg. F?
Your help is very much appreciated.  Again my thanks.
Irving

Answer
Hi Irving,
Well, all depends in how big/heavy the item is. If it is a pair of earrings all you need is 2 minutes but if it is a bangle bracelet you will need 5 minutes, if it is a heavy solid plate you will need up to 10 minutes.
I must remind you that the best annealing temperature for normal softening of sterling silver is between 1100F and 1200F but your kiln only gets to 1000F that is why I asked you to keep the item  for that period of time. I will try to 900F first and then jump to 1000F.
Please let me know the results.

Orlando
www.ocjdesigns.com