Deplating silver-plated flatware

Hello everyone!I got some silver-plated flatware that i would like process for silver.After searching forum it looks like there is few methods for striping silver.Which is the fastest and cheapest?Appreciate your advice.

the easiest way i have found is fairly dangerous. if you are comfortable working with sulfuric acid, this process will work with no problems. make a solution of (by volume) 95% concentrated sulfuric acid and 5% concentrated nitric acid (68% will be fine). it doesnt matter if you are making a quart or a gallon or a drum. 95/5 sulfuric acid and nitric acid. place the material in the solution. you will see an immediate reaction. if the base metal is copper, you will see bright copper when the silver is removed. same with whatever base metal you are working with brass, copper and zinc (i think its ok, GSP would know). to recover the silver without fouling the solution, use salt to precipitate silver chloride. cap when finished. to re-use, you need to add some more nitric acid. only the amount used previously. you will know by the amount of silver precipitated.

Geo said:

the easiest way i have found is fairly dangerous. if you are comfortable working with sulfuric acid, this process will work with no problems. make a solution of (by volume) 95% concentrated sulfuric acid and 5% concentrated nitric acid (68% will be fine). it doesnt matter if you are making a quart or a gallon or a drum. 95/5 sulfuric acid and nitric acid. place the material in the solution. you will see an immediate reaction. if the base metal is copper, you will see bright copper when the silver is removed. same with whatever base metal you are working with brass, copper and zinc (i think its ok, GSP would know). to recover the silver without fouling the solution, use salt to precipitate silver chloride. cap when finished. to re-use, you need to add some more nitric acid. only the amount used previously. you will know by the amount of silver precipitated.

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Geo, what you're suggesting is tricky. Unless you know exactly how much salt to add, you could add an excess and end up with HCl in the solution. This would inhibit further stripping. I guess you could analyze the silver and then add only enough salt to precipitate, say, 90% of it. However, I would expect the Cl- added to immediately generate Cl2 gas when it hits the sulfuric. I've used the 95/5 solution many times to strip silver. When it slows down, I add a little more nitric to perk it up. When it really slows down, I dilute it about 3 or 4 to 1 and then cement with copper or precipitate as AgCl. I might also mention that, for thick silver, this 95/5 solution strips very slowly at room temperature. It is standard to run it about 190F, which is something I would not recommend anyone doing.

i stop adding salt while the solution is still green. thats the way i started doing it and have done it that way ever since. ive had to evaporate the solution twice down to concentrated sulfuric and start over. i cant say how much silver i ran through (i should keep better notes) but the sulfuric seem to be about the same every time. also, when i evaporate, any impurities in the sulfuric precipitates out.

about how much silver is there on a typical silver-plated utensil?

Thank you guys for info.Concentrated H2SO4 is very nasty thing to work with,is there any alternative?I mean to work with sulfuric acid of this concentration :twisted: requires goggles,apron,gloves and maybe face shield.

MysticColby said:

about how much silver is there on a typical silver-plated utensil?

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it depends on the maker and of coarse the wear on the utensil. theres a calculator on the forum somewhere but i cant remember where its at.

flyfisherman said:

Thank you guys for info.Concentrated H2SO4 is very nasty thing to work with,is there any alternative?I mean to work with sulfuric acid of this concentration :twisted: requires goggles,apron,gloves and maybe face shield.

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there is a reverse electroplating cell, but again, it uses sulfuric acid. to remove the silver plating, im afraid you wont be able to do it without using it. if you try to use nitric, it just plates back out on the base metal while contaminating what you do manage to strip off.

About striping silver plate with 95/5 sulfuric-nitric solution,should i keep mixture about room temperature,or heat it up a little? Would it take hours to strip fairly heavy film of silver say at room temperature or it would go faster?Thanks for info :!:

GSP has answered your question, for it to work on heavy plate it needs heat and to be honest you then have a seriously nasty acid mix that will cause severe injuries or worse. I have to agree with GSP this really isn't a process for a home refiner or hobbyist, I have worked around acids nearly all my working life and ran my own commercial refinery but I don't think I would do this and certainly not without good fume extraction, heat control and measurement and proper safety protocols, the amount recovered to me wouldn't be worth the risks.

nickvc said:

and to be honest you then have a seriously nasty acid mix that will cause severe injuries or worse. I have to agree with GSP this really isn't a process for a home refiner or hobbyist, I have worked around acids nearly all my working life and ran my own commercial refinery but I don't think I would do this and certainly not without good fume extraction, heat control and measurement and proper safety protocols, the amount recovered to me wouldn't be worth the risks.

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I agree with nick on the nitric/ sulfuric acid mix. I have personally been tinkering with the reverse electroplating cell for silver plated flat ware, with nominal success. At this point I'm not as much interested in getting the silver, as I am in learning how to get my cell to work effectively. If I was only after the silver I definitely would have given up by now. :|

Although there are exceptions, such as high quality silverware, I would say that most silver plating you'll see is in the range of 50 to 200 microinches thick. In dollar value, that would be from about 1 to 4 cents per square inch of silver plated area. Not much.

thanks, GSP. I couldn't find another post that had the value, I was probably searching for the wrong terminology.
I estimate a spoon and fork have about 5.4 sq in surface area, which puts the total value at about 5 - 20 cents. silver plated knives would have a larger surface area, but is it just the handle that's plated? or am I confusing them with sterling knives?

MysticColby said:

thanks, GSP. I couldn't find another post that had the value, I was probably searching for the wrong terminology.
I estimate a spoon and fork have about 5.4 sq in surface area, which puts the total value at about 5 - 20 cents. silver plated knives would have a larger surface area, but is it just the handle that's plated? or am I confusing them with sterling knives?

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When I gave the 50-200 micro" figures, I was thinking more of jewelry and electronics. For flatware and holloware, it could be much higher. Here's a thread with a chart I found in the very reliable 1967 Handy & Harmon book on silver (written by Butts and Coxe, believe it or not). I don't know how you would tell what the quality is, though, unless it were marked. Maybe the Standard Plate (2 oz/gross of teaspoons) is, uh, standard. It runs about 300 micro" or about 6 cents/inch2. Just remember that all those numbers in the chart are for new teaspoons. Any use or polishing would reduce the value.
http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=46&t=1804

I did more searching on this. The attached pdf gives the US Federal Specifications of silverplate for all sorts of different types of dinnerware. I guess this is for dinnerware used by government facilities (Embassies, officer chow halls, etc.). Note, however, that this entire pdf represents the thickest silver quality given in the chart in the link above - for teaspoons = 9 tr.oz./gross (144 pieces). I guess you could extrapolate the numbers in the pdf to silverware of lesser quality.

For British silverware, I found a reference that said the minimum standard is 20 microns thick = 800 micro" = 14 cents/inch2. In another place, it said the British standard was 35 microns = 25 cents/inch2. Nick (nickvc) is British and is very knowledgeable. Maybe he can add something to this.

I found several references that said they commonly apply 1 micron (40 micro") of silver for each year of intended service. I noticed some silverware that claimed 10 years of service and assume that means the silver is 10 microns or 400 micro" thick.

From a practical standpoint, except for giving an idea of the silver thicknesses used, all this info is probably worthless since it can be all over the map. Whatever you have, it is what it is.

Looks to me that even if each silver-plated item gives 2-3 gramms of silver,the method to recover it with strong acid mix is way to dangerous ,certanly not worth to risk your health for.

I can ask around and try to find out if there are any average plating thicknesses for silver plate but I suspect they are all over the shop. Just to add to the confusion there is also what is known as Sheffield plate this is the early form of silver plated items, it's the silver equivalent of gold filled where a plate of silver is heat welded to a copper sheet and rolled down to the thickness required before been turned into items. To be fair this is usually worth much more than any silver value as it tends to be of 18th century origin.

My math skills are not very good, but looking at this if the silver plating is 0.0025" thick, and silver 0.0025" thick is one troy ounce per square foot ( or 144 square inches) this means, one troy ounce of silver for 144 square inches, or 144 sq in /31.103 g= 0.215grams of silver per square inch.

lets say a dessert spoon is 5 square inches (5 sqin x 0.215g =1.075 grams of silver per dessert spoon.
At spot $32.00/t oz silver ($32.00 / 31.103g/toz = $1.02 per gram).

If my math and figures are correct this spoon has a dollars worth of silver, or a gram of silver.

If I used the same type of concentrated sulfuric cell used on the forum to deplate gold pins with, modify it a little, it would be very interesting to check my math.

butcher said:

My math skills are not very good, but looking at this if the silver plating is 0.0025" thick, and silver 0.0025" thick is one troy ounce per square foot ( or 144 square inches) this means, one troy ounce of silver for 144 square inches, or 144 sq in /31.103 g= 0.215grams of silver per square inch.

lets say a dessert spoon is 5 square inches (5 sqin x 0.215g =1.075 grams of silver per dessert spoon.
At spot $32.00/t oz silver ($32.00 / 31.103g/toz = $1.02 per gram).

If my math and figures are correct this spoon has a dollars worth of silver, or a gram of silver.

If I used the same type of concentrated sulfuric cell used on the forum to deplate gold pins with, modify it a little, it would be very interesting to check my math.

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In that same Handy and Harmon book, it says the Fed Spec plating of 9 oz/gross of teaspoons has an average silver thickness of .00125". That would only work if the area on a teaspoon were about 10 square inches and not 5.4, as MysticColby gave. I just measured the surface area on one of our teaspoons and came up with about 10.5 square inches.

On another subject, it seems that the silver plate on copper wire, if done according to ASTM B298, is a minimum of 1 micron, or 40 micro" thick, which is about $0.007 per square inch at a $32 spot. I think that applies to both stranded and solid wire. I found a lot of references to this. Here is one.
http://www.fiskalloy.com/products/electroplating/

Hi
After a couple of attempts to say that the mixture silver-plated flatware (except knives), eg 10 kg gives about 400 - 450 grams of silver.
Knives have an average of 1,7 g Ag/pc

Large spoons and forks indication 90/45 include up to 5% by weight of Ag
Small pieces (spoons, forks, etc.) have more-to 6% by weight.

henos said:

Hi
After a couple of attempts to say that the mixture silver-plated flatware (except knives), eg 10 kg gives about 400 - 450 grams of silver.
Knives have an average of 1,7 g Ag/pc

Large spoons and forks indication 90/45 include up to 5% by weight of Ag
Small pieces (spoons, forks, etc.) have more-to 6% by weight.

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It seems to be different in different countries. In the US, the Fed Spec teaspoons run about 5.5% silver. However, I would think that most of what is made here is not Fed Spec. My guess is that most is probably closer to what is called Standard Plate. This would be about 2/9 of Fed Spec or 1.2%.