Hi Kara. i have never used the hydro flux system so i can not tell
you if this is the case with this system as new developments are
made all the time but here is my understanding of the no flux
platinum is a material that gets contaminated very easy. it tends to
soak up contaminants like a sponge. the carbon from a gas rich flame
and high temperature fluxes get into the metal and between the
joining areas and create pockets of porosity and coring. on the
outside it might look fine but just under the surface lurks an
incomplete weld that will be brittle unstable.
The melting temperature of platinum alloys and the solders used to
weld them together are so high that most fluxes with burn away and
turn into unwanted residue before soldering temperature is reached.
i am often fixing platinum jewellery that has been improperly
altered using white gold solder and flux. these areas not only split
apart at inopportune moments but more material must be cut away from
the repair area to insure all traces of gold solder is removed
before re-welding. in the case of gold and silver solders used on
platinum they flow at a temperature that is to low to be affective
and act more like glue than a weld.
Platinum is soldered with no flux and using only platinum and
platinum group solders. an oxidizing flame is used not only to get
the heat focused on just the area to be worked but to keep carbon
from to much gas out of the equation.
the material gets very hot and radiates light when soldering
temperatures are reached so dark glasses are a must. you might think
that you are about to melt the metal before the solder starts to do
the job and just at the point you are going to say “oh no this whole
is going to turn into a puddle” the solder will flow wonderfully.
let air cool and do not pickle. clean up is a treat.