Any suggestions on how to spot fake silver?

Archemedis Principle.

http://www.infoplease.com/ce6/sci/A0804583.html

Or, you can put frenches mustard on it, heat it slowely and then wipe away.  If it's real silver, it'll leave a dark spot.  You can use silver cleaner to get the spot off. 

Or, balance it on your finger and whack it with a pencil.  It'll sound like a bell if real silver.  If it thuds, it's not real silver.

http://www.alibaba.com/product-free/105261122/XFR_spectrometer_Gold_Tester_for_platinum.html

There are less expensive options...that's for sure!  But I spend about 75% of my monthly income on PM's.  So I figured I needed something to confirm the authenticity of the PM's.  And "yes", I've been blessed with having enough money to do what I want, when I want.  But trust me, it was hard earned, and there were times I didn't know whether I'd live to see these days.  

The "mustard" test, and other chemical tests will only prove the presence of an outer layer of silver.  They will not reveal a bar that is silver-plated, nor do they allow you to know how pure the alloy is.

The most effective test for metal bars and coins is a simple application of the Archimedes Principle.  When an object is submerged, the volume of displaced liquid is equal to the volume of the object.  From this you calculate the density of the object.  Since each chemical element has a unique density, you will be able to determine whether the density is correct for the object's supposed composition.

First, weigh the piece of metal.  The more accurate the scale, the more accurate your measurements will be.  Preferably you would use a triple-beam gram balance, or electonic scale of equivalent accuracy.

Second, submerge the metal into water and measure the volume of water displaced (or the weight of water displaced, and convert to volume).  Again, the accuracy of your measurements determines the accuracy of the final calculation.

Suppose you have a piece of metal that weighs exactly 1kg, and it displaces 3.25 fl. oz of water (or 95.3 cc).  You simply divide the weight by the volume, and the resulting density is 10.49 grams per square centimeter.  Looking on the periodic table of the elements, we see that only one element has a density of 10.49 g/cc.  The block must be made of pure silver.  On the other hand, suppose that object displaced 107cc of water, making the density only 9.35 g/cc.   You will know immedately that it's not a bar of pure silver (in this case, 25% Ag, 75% Cu).

This test could also reveal the difference between tungsten (19.25 g/cc) and gold (19.30 g/cc) if precise instruments were used.  A 3110g (100 ounces troy) tungsten bar would displace 0.4ml more water than a gold bar of the same weight.  The density measurement would be very difficult with coin-sized pieces of gold, but that is okay, because a coin with a tungsten core would be immediately given away by the fact that it would not ring when flicked into the air.

Note: experienced metal handlers could probably spot a fake silver bar quickly, even without taking precise measurements.  They know how heavy a silver bar is supposed to be for a certain size, and would quickly notice the difference in weight or size.  Also, each alloy makes a certain type of sound when you flip it up in the air or move it around.

The problem with methods to detect fraud is that they assume the fake bar isn't silver coated AND density matched.  I dumped my bars 10 years ago for that reason and now exclusively buy US junk silver.  Small pieces (dimes thru half dollars) are simply not worth the effort to coat and density match compared to a 100 ounce bar, and the natural wear also is a good indicator.

Nate

Purely for entertainment purposes.. Kaiser wields clue stick...

SGT on Fake Silver: