I contacted Caldron Crafts about the copper colored solder they
carry and this is the response they gave me to post on line here.
They had it checked at a independent lab. For those who will be at
the BeadFest in Philadelphia in August, they will have some and will
be at booth 318, you will have to ask them for it since they may have
it in back of the counter.
Sample was given to the lab for assay and results showed it to be
our standard Silvaloy 0 alloy with 7.25% Phosphorus content.
Braze testing was conducted utilizing copper strips approximately
2.5" x …75" x.050" thick. The pieces were cleaned with scotchbrite
pads and overlapped approximately.5 inches. Joint was heated with an
oxy-acetylene torch and wire flowed into the lap joint. Some wire was
flowed on top of the copper strip to get a better view of the final
color of the braze.
Another joint was also prepared only this time the copper strips
were fluxed with WJT Ultraflux before brazing.
The two joints were allowed to cool then soaked in a 15% sulfuric
acid solution for 1 minute and rinsed under hot water and cleaned
with a scotchbrite pad to remove oxide and flux and make the joint
clean enough to view the color.
The joint made with no flux under normal procedures recommended for
this alloy showed a color match very close to the base copper
The joint brazed with the use of Ultraflux showed areas of silver
although the large pool of braze on the surface of the strip still
showed a copper colored match to the strip base metal.
It is recommended that flux not be used with 0 alloys as the high
phosphorus content provides the fluxing action during brazing. It
seems that the flux is reacting with the braze alloy pulling out the
Phosphorus and creating areas of silver color around the main braze
area. Note: An added test was done where the joint was brazed without
flux, however, it was grossly overheated. This produced a joint which
also matched in color to the copper base material.