Authenticating Silver Bars

[Skirnir_]

Due to the irregular shape of most silver bars, caused by engraving, raised edges, curved corners etc., calculating volume is nigh impossible. A bar of incorrect density could be of a different volume than a silver bar of the same weight. Therefore, a device utilising Archimedes' Principle to measure volume by measuring the weight of water displaced would be rather useful, as I fear a slew of counterfeits coming on to the market.

http://img827.imageshack.us/img827/1442/original1x.jpg

The ingenuity of the device lies in that it is not necessary for it to be precise. All that is necessary is for the displaced water to find its way out through the spout.

In theory, this could be extended to gold, though I would be more concerned about the precision of the scale and the displacement of all of the water, as a single drop of water could throw off the measure of a 1oz gold coin by about 3,8%.

[madfranks]

Interesting. Are you planning on building such a device and testing it yourself?

[Skirnir_]

I might build a prototype, but I am concerned that there is not a sufficient market for this to have any economies of scale.

[beefsteak]

appears you are re-inventing the wheel. There are already units which will do what needs to be done in the market place, have a found and filled a unique market niche with, and are quite portable---pocket sized units in point of fact.

They've been discussed on this forum before, back at the height of the drilled and lead filled Engelhard ingots heretofore. Of couse, since all the dumps of this forum and loss of photographs, said make and model may be difficult to ascertain at this late date. Good luck with your stack.


beefsteak

[steyr_m]

I do not think that this is anything new, I think this is the primary thing an Assayer learns.
1. Measure Volume
2. Measure Weight
3. Calculate mass and compare with the charts.

[horseshoe3]

There was a simple and accurate way discussed on GIM. I think it was "The Skeptic" that posted about it.

Put a container of water on an accurate scale. The water must be deep enough that the bar can be totally submerged and not touch the bottom.

Make a hanger out of a paperclip or something similar.

Dip the hanger in to a known depth and record the weight of the water, container, and the hanger together.

Add the bar or coin to the hanger and dip it in to the water to the same depth as you dipped the hanger before. (The coin or bar must be fully submerged at this point.)

Note the reading on the scale now.

The difference in weight will be the amount of water displaced by the coin or bar. Divide by the density of water and you have the volume of the coin or bar.

This method works with all odd shaped objects with a density greater than water. You have to be careful not to spill any water between measurements.