Desperately need help re yogya silver - solid or plated?

[muraille]

Just bought some yogya silver and am befuddled. The first one is marked 800PK. But when I started polishing the back, it developed a slight copperish hue. An acid test however failed to reveal copper under the silver.

The second item is marked B800 and the same thing happened, but it's more pronounced on the front (see upper part of pic).

So the question is, is it plated copper or is it the nature of yogya silver to have a copperish hue? I need help as soon as possible as I bought these items as solid 800 silver, not plated. Thank you in advance for any comments and assistance.
Hotlinks to copper hue: http://b.imagehost.org/0617/925_003.jpg
http://b.imagehost.org/0319/925_005.jpg
http://b.imagehost.org/0524/925_006.jpg

[silverport]

Hello

In a »p.m.« to me »R ingo« reported, that when he restore old spoon, some times he has observed the same. My experience until yet is, that reason for this effect could be twice:

The alloy isn't well made or "mixed".

The object isn't tempered - a must in past time before visiting the warden. I don't know a correct translation for these procedures in English; in an old German it is »Weissgesotten«.

But here in »925-1000« is suggested a non destructive and reliable test method, instead of acid attacks = gravity scale test!

Look to this topic: viewtopic.php?t=11330

Kind regards silverport

[silverport]

Hello

Just I've found this topic in German: http://www.entdecke-schmuck.eu/94464514 ... -t855.html

That is »google« translation: Blanching!

Fine silver retains its white color when heated. The silver-copper alloy on heating and soldering the other hand, is black, because the reaction on the surface of copper contained in red heat with the atmospheric oxygen.
By etching the oxide part are chemically extracted, and the silver alloy gets back its normal appearance.
By contrast to the blanching as all the copper particles from the surface of the alloy are removed, so that this outer zone consists almost entirely of fine silver and acts like one.
As I said, it is now no longer limited to the elimination of the black Glühhaut, but with the significant increase of silver content on the surface of the silver alloy.
You use those Schwefelsäurebeize (usually available at pharmacies. The only wonder what one needs. If we say for the jewelry manufacturing as a stain, they give the acid is usually already out) in 10% concentration and, as the white-boiling can not be otherwise, when hot.
By higher concentration and temperature, the activity of the solution is increased so that, besides the black copper (II) oxide is now also the metallic copper particles can be removed. When red copper (I) oxide is present, it can also be solved. Nevertheless, the zones of deep oxidation, which had been formed under the surface by diffusion of oxygen on ignition, not solved!
Most of the time treatment is not enough to get the surface completely white. Does she still yellow, repeat the operations>> Glow - blanching - Scraping <<repeatedly until the desired effect is achieved.
Such workpieces that are to appear at the end uniformly dull white, sometimes must be dealt with up to four times until the surface is uniformly white.
In the course of time is spent in the Schwefelsäurebeize. Some of the water evaporates, refill occasionally, especially in hot water stains must be so that the degree of dilution is observed. The initially colorless solution turns blue-green because of the increasing accumulation of copper sulfate. As a result, more and more acid parts are implemented in a manner that diminishes the activity of the stain. If the solution is strongly blue-green color, they must be renewed.

Kind regards silverport

[muraille]

Thank you for all the suggestions. I am using the second coaster for "torture" tests, so I'll try the sulphuric acid bath and let you know. In the meantime, I have scratched the back deep enough that it would show copper if it were copper, so at least it's not. Looking at it with a magnifying glass, I wonder whether the .800 alloy was given a finishing dip of pure silver since it is the raised edges that have the copper hue, not inside the hammered crater? Was this a practice in yogya silver? Doing a google search on blanching silver, I found the following, so apparently it's an old practice:
http://books.google.com/books?id=A3UoAA ... er&f=false

[muraille]

Well, I haven't tried the sulfuric acid, but I tried the alum and cream of tartar which are supposed to have the same effect (mentioned in the German article). Indeed, it did return the "golden" hue to a silver one, but it didn't last beyond re-polishing.

What I would really appreciate knowing, since it is evident that these were silverplated to cover the golden color, is whether anyone else has ever run into this with yogya silver? Thank you.