This section is from the "Henley's Twentieth Century Formulas Recipes Processes" encyclopedia, by Norman W. Henley and others.
To solder aluminum it is necessary previously to tin the parts to be soldered. This tinning is done with the iron, using a composition of aluminum and tin. Replace the ordinary soldering iron by an iron of pure aluminum. Preparation of aluminum solder: Commence by fusing the copper; then add the aluminum in several installments, stir the mixture well with a piece of iron; next add the zinc and a little tallow or benzine at the same time. Once the zinc is added do not heat too strongly, to avoid the volatilization of the zinc.
Take 5 parts of tin and 1 part of aluminum. Solder with the iron or with the blowpipe, according to the article in question.
The pieces to be soldered are to be tinned, but instead of using pure tin, alloys of tin with other metals are employed, preferably those of tin and aluminum. For articles to be worked after soldering, 45 parts of tin and 10
parts of aluminum afford a good alloy, malleable enough to be hammered, cut, or turned. If they are not to be worked, the alloy requires less aluminum and may be applied in the usual manner as in soldering iron.
Strong solder: Gold, 89 parts; fine silver, 5 parts; copper, 6 parts.
Medium solder: Gold, 54 parts; fine silver, 27 parts; copper, 19 parts.
Weak solder: Gold, 14 parts; silver, 57 parts; copper, 15 parts; brass, 14 parts.