[So many question have come up about this product and its use that it seems wise to give this piece an encore printing. I hope this gives you more knowledge to put in your stained glass toolbox.]
Sal ammoniac (ammonium chloride), briefly, is a flux used for iron and steel. This statement nearly tells the whole story of why a sal ammoniac block is used to tin (or re-tin) the working end of a soldering iron. Most soldering iron tips are iron or steel clad copper.
Generally, the action of any flux paired with its corresponding metal is to remove the build-up of scale, rust, and oxides (the dark crusts) that begin to form on the surface of metal when it is exposed to even a few seconds of air. Soldering iron tips are no different than copper foil when it comes to attracting and reacting to pollutants in the air. Heat speeds the build-up of oxides. (The fluxes used to clean copper foil and zinc in preparation for soldering are a suspension of zinc chloride. Historically, tallow and palm oil were used as a flux for lead soldering. Oleic acid has replaced tallow.)
So, how does it work? Placing the heated metal on the sal ammoniac bar melts and partially decomposes the layer of flux (remember, sal ammoniac is a flux) in contact with the hot metal (the soldering iron tip and a drop of solder). As the sal ammoniac “sublimes”(creating that nasty smelling white smoke), the hydrochloric acid part of the compound is liberated. The hydrochloric acid is what dissolves the oxides from the metal surface of the iron and enables tinning. More science than you wanted with your coffee today I bet!
A few warnings about using the sal ammoniac bar:
- Use adequate ventilation during this process.
- Sal ammoniac is abrasive and excessive use can wear away the iron cladding.
A few tips on tip care:
• Keep your tip clean with a wet sponge while working, but avoid constant wiping which will cause the temperature to rise and fall dramatically causing metal fatigue
• At the end of a soldering session wipe the tip clean, “flood” with solder, then wipe again and unplug the iron.
• Don’t allow the iron to “idle” at operating temperatures for extended periods.
With good care a good soldering iron and tip
should give years of service. However, there are
soldering irons out there that do not meet even
minimal standards of quality. So, buyer beware
– it’s a good rule of thumb.
Using the sal ammoniac bar requires some patience; it is not actually working until you see (and smell) the white smoke. When tinning your soldering iron tip with the aid of sal ammoniac, make sure the iron is very hot. Come in to Jones Creek Glassworks for a demonstration (my soldering iron tip can usually benefit from a good tinning).