Richard Allen

   Make your own Silver Solder

The advantage in using silver alloys for brazing instead of inexpensive brass is that a much lower temperature is required, which makes for an easier job, and the resulting joint is usually much stronger. About ten years ago I needed some silver solder for general shop use, and when I went to the welding supply place to get some I left without buying any. The stuff is insanely overpriced, it cost many, many times more than 999 fine silver itself! I researched several popular formulas for non-cadmium silver solder alloys and have made my own ever since for 5% to 10% of what it sells for in welding supply stores. The major drawback is that turning it into wire is not practical for most people, wire drawing equipment is necessary. However, making it into a sheet then cutting into strips with shears is easy. For those of you not in the United States, making the alloys will be more difficult because the method of alloying I use depends on the use of OLD U.S. coins for raw material!
The dimes and quarters mentioned are all pre 1965 dated, 1964 being the last year that the U.S. used 90% silver 10% copper alloy for coinage. The cents used are pre and post 1982, don't use 1982 itself because in that year the coinage was mixed with both copper based and zinc based coins issued. I buy my silver coins from a local broker who charges the going rate for U.S. coin bullion. Canadian silver coinage used to be 80% silver 20% copper, and U.K. has been all over the charts. All the really valuable coins have been picked out so that the ones sold have no esthetic or historical value. The coins can be melted in a jeweler's or graphite crucible, I have used both over the years. Usually a large propane or MAPP torch is hot enough to make the melt, but it is much faster with an oxy-acetylene torch. Just be careful not to boil and burn out the alloy. It is absolutely essential that the coins be melted in the order of silver, pre 1982 cents, tin, then post 1982 cents last.!
 It is also necessary to add borax to the coins as they melt. Regular laundry borax is fine, but it fluffs up enormously before melting. Add borax copiously while only the silver coins are in the crucible, then continue adding it during the melt. The post 1982 cents (zinc) will burn violently unless they are rapidly and completely submerged in the molten metal. Even then a lot of the zinc will boil away unless the melt is stirred and allowed to cool somewhat as the melting point of the alloy adjusts as the zinc dissolves into it. A #2 graphite pencil makes a good stirrer, the wood will burn back but enough usually remains as a heat insulator for the fingers. As a quality control, weigh all the coins and tin before melting, then re-weigh after melting. If it is not within 95% of the pre-melted weight, it will have to be melted again and have more post 1982 cents added until the final weight is correct. Any lack in weight will be due almost exclusively to loss of zinc. Silver do!
es not oxidize at all, and the copper and tin WILL NOT oxidize or burn out in the presence of zinc, the zinc ALWAYS goes first! When you are sure the alloy is finished, pour it out onto an OVEN DRIED very smooth non-porous clay masonry brick. It will spread out into a thin sheet if you help it by squashing the puddle with another dry very smooth non-porous clay masonry brick. After it is cooled it can be cut with sheet metal snips into strips and paillons, or granulated with a clean and sharp fine file. Plain laundry borax will work as brazing flux IF the parts being silver brazed are heated hot enough to completely melt the borax so as to completely cover the area to be brazed. It is actually much easier to use regular silver solder flux, but unfortunately, silver solder flux is very poisonous and makes very poisonous fumes due to its high fluoride content (yes, same stuff needed for strong teeth is very poisonous unless in small quantities!). It can be used safely only with !
good ventilation and cleanup afterwards. Borax is extremely safe, and has an excellent track record of several thousand years!

These alloys are safe to use for food handling items, and are also standard alloys for temperature step brazing in silversmithing.

51.5% silver easy braze: Melting point ?
Silver 51.5%
Copper 25.5%
Zinc   17%
Tin     6%
Made from: 1 quarter, 1 dime, 1 pre 1982 cent, 1 post 1982 cent, 15 grains (0.97 gram) tin

56% silver easy braze: Melting point solidus 1145 to liquidus 1205 F
Silver 56.152%
Copper 22.085%
Zinc   16.471%
Tin     5.292%
Made from: 5 quarters, 7 dimes, 4 pre 1982 cents, 5 post 1982 cents, 67.5 grains (4.4 grams) tin

65% silver braze: Melting point solidus 1240 to liquidus 1325 F
Silver 65%
Copper 20%
Zinc   15%
Tin     0.0%
Made from: 4 quarters, 11.5 dimes, 3 pre 1982 cents, 4.5 post 1982 cents, no tin

70% silver braze: Melting point solidus 1275 to liquidus 1360 F
Silver 70%
Copper 20%
Zinc   10%
Tin     0.0%
Made from: 9 quarters, 1 dime, 3 pre 1982 cents, 3 post 1982 cents, no tin

75% silver braze: Melting point solidus 1365 to liquidus 1450 F
Silver 75%
Copper 22%
Zinc   3%
Tin     0.0%
Made from: 14 quarters, 1 dime, 5 pre 1982 cents, 1 post 1982 cent, no tin

90% silver braze, industrial use only. Melting point 1640 F
Silver 90%
Copper 10%
Any pre 1965 U.S. silver coin

Work and play safely,-------Richard Allen