I could use sterling silver sheet that has a thin layer of
silver solder on one side.
Does anyone know if such a product exist and where one might purchase
it in modest quantities?
Some suppliers, like IJS and RGA used to sell such a sheet under the
name of “solder-flushed sheet”, but no longer carry it. Perhaps some
other supplier still carries it.
Another way to accomplish having just a thin layer of solder is to
use powdered solder. Make a slug of solder large enough to hold onto
easily, or use sheet solder. Scrape the solder across the slug or
sheet until you have a small pile of powder. I do this onto a paper
plate because it’s easy to fold into a funnel. You have to use a file
rather than sandpaper or cutting disks. The reason why is you can’t
remove the contaminants from the powder. After you have a pile of
solder powder, take a very strong magnet and draw it through the
powder thoroughly. This will remove any metal filings which will
contaminate your solder.
Next dip the piece you want to sweat into flux, preferably a thinned
out paste or liquid type. Let the excess run off, and dip the piece
into the powdered solder. Tap the piece gently against an edge, and
the excess will fall off. Place it onto your metal you want to sweat
it to, and heat, preferably from underneath. It will suck down like
magic, perfectly and with no leftover residue.
I kick myself everytime I try to sweat solder something without doing
this, because I will either have too much, not enough, or air pockets.
Powdering the solder is worth the extra trouble. K.P. in WY