Silver bars are typically .999 pure silver, meaning other metals have not been used to alloy the silver. Silver bars are an easy way to own bullion, and unfortunately, some fake silver bars are out there. Doing a simple test can make sure that the silver bar that you buy is genuine and pure silver as advertised. Silver bars are most commonly found in 2835gr sizes.
Know your source. The primary protection against buying counterfeit silver bars is to know who you are buying your bar from. Reputable coin and jewellery dealers will only sell legitimate genuine silver bars and making sure that you get an invoice that mentions the serial number of the bar will protect you. If you are paying a price that is below the current price of silver, you have reason to be worried.
Look at the maker of the bar and weigh the bar. Silver bars are typically stamped by the maker. A handful of bars have recognised hallmarks that make them readily accepted for resale. Hundred-ounce bars are the most common, and a 2835gr bar weights 3.11 Kilogram on a bathroom scale. Engelhard and Johnson-Matthey are two of the larger producers of silver bars, but others include Sunshine Minting, Wall Street Mint, Sheffield and Handy & Harman bars.
Perform an acid test. Short of a destructive acid cut to see the centre of the bar, an acid test is the best way to determine the composition of a metal. Scratch the metal on the side of the bar, then apply the acid and follow the directions. If the metal changes colour, it is likely not pure silver, and the metal below will be revealed by matching the colour with the colour chart provided in the kit.
Remember that different acid testing solutions provide different results. Treat silver bars from minor manufacturers with a healthy dose of scepticism.
When using acids, avoid contact with eyes and use in a well-ventilated area.