which wore fastest in circulation .925 or .500 silver

[Britannia47]

Thought you might like a comparison photo of Half-crowns in .925 and 500 silver with the last Cupro-nickel/zero silver. Nickel does the job but is the worst of the alloys. It bleaches out the copper big time to make it look silver, but in fact has been known to be slightly carcinogenic, with some people allergic to this metal, causing dermatitis. The EU and USA I believe are reluctant to use it in coinage? No problem with gold though😃!!

 

[DaKine]

The British Museum in the backroom has many GB coins from this era including samples of the different alloy coins; I recall about 20 years ago going through these. Now with XRF we have an ability to instantly analyze. I have some specimens that I would very much like to check for composition. As a sidetone some of the patterns appear to be struck on blanks that had a silver wash.

Also I do recall reading of the RM pickling blanks prior to striking to give a surface "micro layer" of higher percentage silver than the rest of the blank.

[stefffana]

Hi, all!

As I have promised you, I've done an experiment using four coins threepence, different years, to cover all four compositions. I have tried to have relatively similar initial weight and grade.

I have rubbed them on seven rounds, applying the same treatment for all of them, the same finger pressure and the same number of up-down courses, using sand paper 40 grit for Round 1, 100 grit for Round 2-3 and 220 grit for Round 4-7. 

Of course, because I have not specific tools to measure the pressure and very accurate scale, this experiment it is not a very scientific one and my results are only pseudoscientific. But it is better than nothing. I have weighted three times every coin, and the recorded and valid weight was an average or the weight showed by scale two times. The recorded weight can be a little different than in pictures, with a difference of +/- 0.01g.

The coins used for this experiment are below, with pictures before and after:

1. 1917, 0.925 silver, 0.075 copper, weight initial 1.43g, final 1.23g, losing 0.20g.

 

 

2. 1921, 0.500 silver, 0.400 copper, 0.100 nickel. Initial weight 1.40g, final weight 1.19g, losing 0.21g

 

3. 1925, 0.500 silver, 0.500 copper. Initial weight 1.41g, final 1.20g, losing 0.21g.

 

4. 1936, 0.500 silver, 0.400 copper, 0.050 nickel, 0.050 zinc. Initial weight 1.40g, final 1.15g, losing 0.25g.

 

The initial, intermediary and final weights and total loss of these four coins are recorded in this chart:

The pictures are not great, but I've done the best I was able.

Conclusions:

In term of resistance,

0.925Ag/0.075Cu alloy lost less, 0.20g, but what is interesting, is almost blank now, unrecognizable.

0.500Ag/0.400Cu/0.050Ni/0.050Zn alloy lost 0.25g, apparently the worst, but again it is interesting, it is not blank, still having some details.

0.500Ag/0.400Cu/0.100Ni and 0.500Ag/0.500Cu lost the same 0.21g. Nothing to add about condition. George V is still there a little, in the mirror.😊

I hope this experiment will be useful for all of us. Can be repeated by another TSF member, having a total cost of @£10 (coins, sand paper),but is time consumer (@3h for me).

All the best!

Stefan.

 

 

[James32]

I thank you for your dedication 👌

[ArgentSmith]

Sterling comes out on top with the zinc alloy showing a massive loss of weight. Excellent work!

 

 

[ady]

WOW, What dedication and fantastic trial, hope everyone appreciates how much of your stack you have lost doing this!

[Centauri167]

@stefffana: Great work you did there, very interesting of reading and seeing the conclusion ! 👍

[DaKine]

I wonder how much density has to play in this? I would assume that more silver would be more density. This would be important as to how much material was lost...