Back to Ganoksin | FAQ | Contact

Casting old coins


#1

I have some old Canadian coins minted in 1950 which Iwant to use in
casting. However, I want to raise their silver content to that of
sterling. I have some fine silver casting grain that I can add to
the melt but don’t know how much to add. I learned that their silver
content is 80%.

I have been trying to figure out how much fine silver to add to each
gram in the melt in order to raise it to sterling.

Granted it would be a lot easier for me to just forget using them
and to get some sterling grain, but the coins have sentimental value
to me, and I want to cast them into rings for the women in my
family.

I have searched the internet, but have not been able to find out how
much fine silver to add per gram in order to create the sterling.

Is this something that I can do, Or should I just forget the entire
matter. Alma


#2

If the resulting jewelry is for a particular person and you dont
stamp it sterling, why not just use it as is as long as the person
knows that it is coin silver. A lot of native american jewelry is
made of coin silver.

fred


#3

You will need to add 6 grams of pure silver to 4 grams of your coins
so in other words 400 grams of coins need 600 grams of fine silver
to make 1kg of sterling silver.

Nick Royall


#4

I have not done this before, but I think I can explain the basic
algebra, and I’m interested in what I’m learning on Orchid so want to
help where I can :slight_smile:

Sterling being 92.5% and Fine being 99.9%, and starting with 1g of
80% (the coin),

1g c.80 + Xg c.999 = (1+X)g c.925 [converted percentages to decimal]

so, solving this for X, [and dropping the gram labels] .999X -.925X
=.925 -.80 [intermediate step]

then, .074X =.125
so X = 1.6892 [rounded to ten-thousandths]

where X is the number of grams of Fine to be added to each gram of
80%-silver coin, to achieve sterling. Can anyone check my work?

Cheers,
Ben


#5

I am not certain, but if I was to attempt it, this is what I would
do. Take the total weight of the coins that you are going to convert
to sterling silver. Multiply the weight by 0.8 to determine the
amount of fine silver; the remaining weight will be the alloy. Now,
divide the weight of the alloy portion that you just determined, by
0.075 (sterling is 0.925 fine and 0.075 alloy). This will give you
the total weight of sterling silver that you will be making based on
the original amount of alloy that is in the coins. Now subtract the
total weight of the coins from the total weight that you now
determined for the sterling silver, to give you the amount of fine
silver to melt with the coins.

For example, 20.0 dwts of coins x 0.8 = 16.0 dwts of fine silver and
4.0 dwts of alloy 4.0 dwts of alloy / 0.075 = 53.3 dwts of sterling
silver (49.3 dwts of fine silver and 4.0 dwts of alloy) 53.3 dwts
sterling silver - 20.0 dwts of coins = 33.3 dwts of fine silver


#6

Thanks to all of you for the helpful on raising the
silver content of old coins. I will be giving it a try. The biggest
problem will be cutting the coins into smaller pieces so that I will
be able to measure out the weight needed for each piece that I will
cast. Also they will melt down faster with my torch.

Thanks for doing all the math for me. As Nick pointed out, one would
use 6 grams of pure to 4 grams of my 80 % silver. If I understand it
correctly, this would be 1-1/2 grams pure for eachgram of the 80%
coin silver.

If I have understood it correctly, the procedure I would follow
would be tofigure out the total amount of silver I need, for each
model, Then use 1-1/2 grams of pure for each gram of the 80% silver.

For example, if total amount of silver needed is 10 grams. ThenI
would use 4 grams of the coin, and add 6 grams of the pure. If 16
grams is the total amount needed I would use 10 grams pure, to 6
grams of coin.

Hope I have figured it out correctly. Thanks again for all your
help. Alma


#7

I suppose you could cast them uniface, but trying to make exact
duplicates would be counterfeiting and probably not good to do. If
it is just that they are Canadian and not the specific coins or
dates you could just get earlier examples, Canadian coins before
1920 are sterling. So are some of the special issues.

Ben


#8

Oops. Just reread all the posts on raising 80% silver to sterling.
Found out I need to add l.7 grams of pure for each gram of the 80%,
and not 1.5 grams. Good thing I rechecked and saw that I was not
figuring it right.

Good thing I caught it before I begin this project.

Alma


#9

What does it matter what they turn out as. Add some silver to the
melt and cast them. The complete metalsmith had some info on raising
gold values maybe try there, see if there is something for silver


#10

Sorry if this duplicates previous responses. There must be a way to
calculate the needed amount of fine silver needed, but it escapes me
at the moment. However, there is a specific entry in Harold O’Connor:
The Jeweler’s Bench Reference. “To 1g of 800 silver, add 0.865g of
fine silver to get 1.965g of925 silver.” (Not sure how those weights
work out though :wink:


#11

That’s definitely a typo, John" 1g + 0.865g is 1.865g, not 1.965g
(the 9 is the typo).

Sorry to be a “math nerd”, but this is a standard “mixture” type
problem in algebra, here is a page site that has some review for those
of you willing to understand the maths:
http://www.ganoksin.com/gnkurl/ep81nh

the bottom of that page has an example that pertains (the acidic
solution), also some on the second page. If you fear math, don’t look
at the whole page, just follow along one word at a time, one step at a
time.

It is a classic middle school problem and all the more reason why
math IS important and DOES play into the real world :slight_smile: The point is to
know what you’re working with, and to be able to adapt what you have
to what you need, Shannon. :wink:

Anyone who missed it, and wants to know: please look back on my post
from 5 days ago; 1.7g of pure per g of 80% will get you just past
where you want to be, or more aptly, it will allow for a margin of
operational error (scale accuracy, oxidation, etc).

Cheerio y’all,
Ben

PS - Tangentially: Do most of the group members’ customers seek sterling
quality, or is “silver” enough to satisfy sales needs in most cases?


#12

Hello,

For what it’s worth, I happened to be reading the (Canada) Currency
Act the other day because I was interested in the legality of
piercing out designs from coinage to make jewellery and had questions
about it (okay, I’m also a bit of a nerd with law/policy).

Article 11 of the Act states: “No person shall, except in accordance
with a licence granted by the Minister, melt down, break up or use
otherwise than as currency any coin that is current and legal tender
in Canada.”

I honestly don’t think that the minister of finance will devote the
effort to stopping you from melting down pre-1968 coinage (when the
Canadian silver dollar switched from 800silver/200copper to 1000
nickel), because they have other things to worry about, but I
wouldn’t go about making a commercial endevour of it–not publicly
anyhow.

Regards,
Mark


#13

Mark, I got a chuckle out your about the legalities
regarding the “defacing,” of coins. I could just see a contingent of
red coated royal mounted police —we called them "Mounties,.
storming into our studios to arrest us. Ican just see the headlines
in the papers now, as they tote us off in shackles—you toting your
pierced coins, and me lugging some melted globs. I agree, with you
that we are safe, as they certainly must have some more serious
things to tend to. Besides, what I create will not be for sale, but
will have been given new lives as pendants for my kith and kin.

Things have been getting so serious here with some heated
discussions, thatyour post was a welcome change. Alma


#14

Mark, I’d be interested to hear what happens if you should write to
the Minister and ask for said license…

Waving from the sidelines, Betsy


#15

I used to know the legal jumbo in the US but as long as you are
increasing the value of the coin or currency it is not illegal to
deface it or change it. The problem comes when people melt it down
and sell it for less that undermines the Gov.


#16
The problem comes when people melt it down and sell it for less
that undermines the Gov. 

Huh? I suppose that this would be a losing proposition for making a
profit.

Could it possibly be the inverse?

J Collier


#17

The U. S. Gov. Is making money for a profit. ever sense they stopped
backing their money with gold and silver. What we now have in our
hands cost them much less then what the face value of the currency
they made. except I think the copper penny now might be close to
equal, that is why they are talking about stopping making them any
more…


#18

That would mean selling for less than face value as the govt has
decided that despite the intrinsic value of the metal they will only
pay you face value should you hand it over to them.

So for example, a $20 gold coin should be handed over to the govt in
exchange for paper bills of that value and never mind that it will
scrap at $1000 or be worth at least 3 times that to a collector.

This is how governemnts throughout the world control your wealth, by
taking from you something that has an intrinsic value and exchanging
it for a promise that it knows cannot ever be kept. We all play
along with this deceit because none of us are self-sufficient.

Nick Royall


#19

I’m pretty sure the government loses money on printing or minting
money/coins now. And if anything, it was individuals who use to
profit from the fact that coins use to be made of gold. This is
because they would clip or file little pieces off and turn in a good
pile of it for profit.

However, the government does not need to make money with coins
anymore.

The most profitable gig they have going now in the U. S. are student
loans.

They make a few billion a year on student loan interest alone. In
most sane industrialized countries if you pay the loan for 20 years
they forgive the rest. Here, a person cannot ever get rid of them in
any way except by paying them which wouldn’t be a problem if tuition
had not increased 300% since 1980. One of the many reasons our
economy is falling apart after 35 years of destructive economic
practices.

Anyways it is interesting that coins use to be made of silver or
gold here. I tell me young students that and most of them never know
that.

Rick