I am not sold on retipping with laser welding, any one haveing
good luck doing it Rick
In white golds, with argon, or with platinum, you can retip white to
near white diamonds with the laser. use the lowest power settings
that will let you build up the metal, and try to aim the laser at the
metal, not the stone, being aware of where the beam will reflect from
the metal, as well as where it will directly hit. I use a filler
wire, either platinum or white golds, of about .25mm for retipping.
The key is that diamond, if clean, will transmit most of the energy
that hits it, rather than absorbing it at the surface, and with the
thermal conductivity of diamond, the whole stone heats up, again
absorbing the energy instead of burning. But this isn't completely
risk free. Avoid working on highly included stones, and know that an
inclusion right where the laser energy hits or reflects, will
increase the chance of damage. At higher powers, you CAN very
certainly burn or shatter a diamond. The girdle, too, if
unpolished, will be affected if you hit it. As with torch retipping,
the stones should be clean before you work on it, though it's a
little less critical. If you're building metal out over the stone,
rather than just increasing the thickness of what's there, lay the
wire against the stone, up against what's there, and try to "shoot"
the metal of the wire, at the junction, up into the existing metal.
The idea is to find a setting where the penetration acheieved in
this is almost to the stone, but not quite. Sometimes it's best to
remove the existing tip, lay a piece of flattened wire the dimensions
of a prong tip down, and weld it to the stub of the remaining prong
just above the girdle, in much the same way you might put a new tip
on with solder. Advantages of laser retipping, especially when
building up a merely worn tip that one might otherwise be tempted to
do with just solder, is that the work hardening effect of the laser
means your new tips will be really wear resistant, over and above
just the fact that this isn't solder, but is solid good metal. If
these are diamonds that can in any case take torch heating, then I
sometimes lightly anneal the tips after building them up with the
laser, since sometimes laser welds are a bit too brittle for safety.
Of course the normal cleaning and coating with boric acid is needed
for this, but then I only heat the tips briefly to just barely
glowing for a moment, or sometimes just enough to glaze over the
boric acid. not a full annealing process, just enough to stress
relieve them. This process is also useful in those cases where the
welding has left a bit of black "smoke" on the piece, since the boric
acid coating will take it off more effectively than even the steamer
or ultrasonic, from recessed areas.
Try it with some broken/chipped diamonds for practice, first.
As to retipping on anything other than diamond, well, sometimes you
can get away with it, especially on lighter colored stones, but in
general, most of the colored stones will be damaged if the laser
energy hits the stone, either directly or by reflection. If you
really hit a colored stone directly, you'll usually shatter it.
Slight amounts of reflected energy cause the more common canage, a
small melted/glazed over area, with or without a bit of crazing of
the surface there. When this happens, sometimes the stones can be
saved with a bit or repolishing or minor recutting. The darker the
color, the riskier it is. I usually agree to try it only when the
owner takes the responsibility for damage, and understands there's a
good chance of that occuring.
Sometimes, with a prong, you can bend the prong away from the stone,
build up the tip, and then return it to the stone, with the stone
being protected during this process with either a layer of fimo clay
(we use a dark blue, but I'd imagine any opaque color should work) or
with a heavy coating of white out. White out isn't as reliable, but
it can help a lot in at least partially protecting a stone you're
welding near to, if the distance isn't enough for a bit of fimo to be
packed into the gap.
Hope that helps.