Chemical (Ag) Makeup of Silver Plates – URGENT

[jluca]

I am a student of photographic conservation at the Performing Arts

Academy in Prague Czech Republic.

I am writing my thesis on dags and studying the effects of peroxides

and sulfates in the air through artificial aging. I need to make some

test dags to try my aging process on for research purposes and I am

trying to find information on the chemical makeup of dag silver

plates, I can order plates here in the Czech Republic that are

AgNi0.14 or AgCu or then an alloy material that is AuNi5 or AuAgNi but

I cannot find information on what was used historically.

I was wondering if you had any information on this that may be

helpful. I searched for historical literature of the process and all I

could find is that some practitioners melting the silver from actual

coins anther silver (household) objects, but I want to be as accurate

as possible so my research can be repeated by anyone.

If there are any thoughts you may have, or can point me in the right

direction I would really appreciate it. I would cite you in my work of

course! Thank you in advance

[Andy Stockton]

Generally contemporary daguerreotypes are made on a pure (.999 fine) silver surface. The base plate is usually copper. The silver layer is electroplated or Sheffield clad. The thickness of the silver varies with the process used, but 10 microns is common. A few practitioners work with pure silver plates.

The exact nature of historical plates may vary, but other members of the list would have to chime in on that as I have no expertise there. In most discussions I have read, the more pure the silver of the image layer, the better the daguerreotype, and that was as true in the past as it is today.

You will find various materials on the resources pages of this site that will lead you to further information. Good luck with your study.

[Mike Robinson]

A good resource on the manufacture of silver plates for the daguerreotype is the book

Daguerreotypes, 19th Century Practice and Modern Science by Barger and White.

The majority of 19th century plates are silver clad over copper by rolling (American made) or hammering (French made).

Later in the daguerreian era one company (Christofle of France) provided electroplated plates but by far the most common was clad silver plates.

The silver is as pure as possible .999 fine. The silver thicknesses ranged from about 10 – 20 microns before polishing.

Polishing was necessary to remove the rolling mill or planishing hammer marks.

Regardless of the make, French. American, clad or plated, about 20% of daguerreotypists re-silvered their plates with a galvanic deposit of silver after first creating a fine polish. The usual method of determining if a plate has been re-silvered will be to look for a poorly adhered deposit of silver on the back of the plate.

I sell NEW clad plates to those that want them. The silver is .999 fine approximately 25 microns thick. The total thickness including copper is 0.020 inches thick.

They require polishing to remove the rolling mill surface.

best

Mike Robinson

[Author]

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