Today I decided that for the fun of it I would smelt the jars of solder tailings that I have accumulated over the last 4 years. I have been very faithful in collecting the scraps and splatters as well as the solder collected from desoldering and salvaging circuit boards. Not only do I want to be environmentally conscious but I also want to avoid the damage that happens to the floors when solder and scraps of metal get embedded into the wheels of the shop chair.
I began the process by making a bunch of small trays out of aluminum foil by shaping them around a small bread board. After the bread board was removed the tray remained. Since aluminum has a lot higher melting point (660C) than the solder alloy (200C) the little trays, despite being very flimsy, would hold the molten solder until it cooled and then since there is no adhesion between solder and aluminum the foil tray could be easily peeled away.
I had a small propane torch and a small cast iron ladle. As I heated the collected solder the lead and alloy began to accumulate in the bottom of the ladle. I stirred the pot as I continued to heat the molten metal. The heavy metal sinks to the bottom and the oxides, lighter debris and carbons rise to the top. A heavy flat screw driver was used to whisk the slag on the top of the metal to the side and over the edge of the ladle. Once the remaining metal was all shiny and looked like mercury it was poured into one of the aluminum foil trays to cool.
This process was repeated until all the accumulated solder had been processed. I then prepossessed the slag that I had scraped off the top of each batch and was able to get another pour of the pretty silver metal.
Just to make sure I didn't burn my fingers in my haste I put each tray into a bucket of water to complete the cool down and then peeled the tray from each piece. My net haul was 9 rectangles and one small blob of solder alloy. As I sat with the result of my labors in my hand I decided to indulge my imagination and pretend that it was Gold and not Lead. After all there are only 3 very small protons of difference from one element to the other.
According to today' metal spot prices this Kilo of metal would be worth $38,000.00 if it was Gold. Unfortunately it is Lead and the $2.00 that it is worth will not even provide reimbursement for the propane that was spent to extract it.
In its present form it will be much easier to store and I often use pieces of lead like this to provide weight when needed in the base of some of my projects.
If you decide to try this yourself use caution as there are many opportunities to burn yourself and or start a fire. I went outside and worked on a large stainless steel table. The fumes that are created are copious and if done indoors you will need a ventilation hood and an extremely understanding spouse.