Is it Sterling or Silverplate? How do you tell?

[larrywseale]

The only real problem I've ever encountered was a Towle "Old Colonial" serving spoon that had no markings other than Towle. The rest of the set was marked sterling & I could find no evidence that "Old Colonial" was produced in silverplate. Still, I wasn't certain so I asked for advice in the forum and learned about hydrostatic weighing to get the specific gravity. Lo & behold, it turned out the piece was silverplate so I'll pass the info along.

According to Archimedes' Principle of Buoyancy, an object weighs less in water than in air due to the upward thrust of the water so we can get the specific gravity by first weighing in the air, then in the water & calculating the difference in weights, i.e.

weight in air
_________________________ = specific gravity

weight in air - weight in water

All that's needed then is a table listing the specific gravity of whatever you're testing for. Fine silver (.999) has a specific gravity of 10.49 & sterling (92.5% silver & 7.5% copper) is 10.36. Copper is 8.96 & 18k yellow gold is 15.58. In my experience, plate is usually around 9 but it depends on the metal used. Works for metal, gems, etc.

You'll need a balance beam scale, some fishing line & a bucket of water big enough to hold your object. Attach the fishing line to the scale platform & zero it. Attach the object to the fishing line & weight it in the air. Submerge (still tied :-) the object in the water and weight it again.

It's not 100% accurate but it's close enough. I use a Ohaus Triple Pro designed to hang objects under the platform and I also have an Ohaus CENT-O-GRAM (used, about $25 on eBay) that worked fine until I wanted to weigh something over 311 grams.

Hope that's helpful. -larry-

ps. I should point that this only works for solid objects. Hollow sterling beads, for example, will trap air which gives you a false weight in the water unless you can remove 100% of the air. If you were in a lab, you'd control the temperature of the water also but in the kitchen, it's close enough that you can determine what you have.

[larrywseale]

I know this is sacrilegious but no one has mentioned acid testing. It mars the piece being tested so it should only be done on scrap or in a place that is very inconspicuous. You can use fuming (65-70%) nitric acid but beware, it's called fuming for a reason and it's NASTY stuff. Use only in a very well ventilated space and be very careful. Even a tiny drop will give you a bad burn.

A somewhat safer (not more but a little because it's more dilute) & more accurate alternative for 90% or better silver is Schwerter's solution made from diluted nitric acid & potassium dichromate. It has a somewhat short shelf life so I'd recommend trying to find a local jeweler that will sell you a small amount & not buy it premixed (usually called silver test solution) over the internet.

You can either use a test stone or test on the piece itself BUT you're going to mar the piece regardless. First, you have to remove any plating in the area to test. You can rub the piece against the stone until you're sure you're below any plating or scratch/file away any plating. Put a drop of nitric acid/Schwerter's solution on the metal mark on the stone or on the piece where you scratched/filed it.

You get a reaction and you check the color.

Nitric Acid
.9 - .999% = creamy color
.77 - 90% = grey color
.65 - 77% = light green
< .65% = dark green

Schwerter's solution
.999 = bright red
.925 = dark red
.9 = reddish brown

Any other color tested with Schwerter's solution & the silver content is less than 90% (might be platinum or white gold :-). It might be hard to judge the color so a check is to test a something with a known silver content and compare the results, i.e. testing a piece of marked (scrap only) sterling or testing gold on a stone where you make a mark with the piece and a mark with a known purity gold needle. Gold & platinum testing is a discussion for another place & time. -larry-

[Hose_dk]

In July 2007 I wrote this:

"I have tried testing silver. A product called Probiersäure für Silber from Ballerstaedt & co tel +49(0)7222 95150. You put one drop at the item. If it is silver it turns red if not it remains brown. It is true that silverplated also turns red, I scrach a bit at the edge of the item. You dont realy destroy the item. Afterwards it is almost invisible. You have to know where it is. You just add asid to the scratched part.

In theory you should be able to determin 800 fra 925 silver. The more silver the more red it should be. Take a picture for reference. But mind picture should be taken in same light and same amount of seconds after you have aded the asid.
I have not been able to do this - i soppose try and error - try and error should be performed a number of times.
When I tested 688, 750, 830, 925 and silverplate. the 11L (688) silver came out whit the most red colour. I think that I just need to pratice more bu havent had the time."

I tried to find a post where I described my proces but I soppose its long gone.

Also in this we discuss the subject.
viewtopic.php?f=38&t=6550&p=13732&hilit=testing+silver#p13732