However, I did do a bit of a web search and found that Otto Frei
has a pink/rose gold high copper content hard solder which they say
is cadmium free.
Do you know anything about this solder. Does it flow well and does
it maintain its pink colour?
I haven't specifically used Otto's rose gold solder. But they are
not direct producers of solders, and carry that of various
manufacturers, so I'd bet theirs is similar to the rose gold solder
I'm familiar with, which is also "hard" grade, and cadmium free. As I
noted, the color match is decent, not perfect, but probably about as
good as you'll get. And it's a higher melting point solder so needs
some care/skill. The stuff I have tends to be a bit sludgy, not
flowing so easily, but it's important to note that this property of
how well a solder flows in a joint has a lot to do with the metal
you're soldering, not just the solder, so slight differences in the
rose alloy of the metal you're working with can affect those
behaviors a lot. Specifically, if you add a little of the parent
metal to a little of the solder alloy, would the result have a
higher or lower melting point than the beginning alloys. Solders tend
to flow better when the resulting alloy melts slightly easier, but
not much so, or the volume of melted metal would increase. If the
result of adding the solder alloy to the parent would raise the
melting point, that will tend to inhibit the solder flow a little.
That is still better than if the solder causes the parent metal to
slump into the molten pool. But anyway. With these high copper
alloys, and given the copper is one of the metals who's percentage is
varied to create solders, slight differences in the amount of copper,
or silver, can have dramatic effects on the performance. However,
with skill, a good flux, and careful control of the heat, remembering
that solder will flow towards the heat in addition to along a
capillary seam, you can get almost any solders to work with
Hope that's of use.