Personally, Steve, I disagree with you about that line of
blocks, which is not exclusive to Gesswein, of course.
The block is highly sintered, which results in nice durable
surface hardness, but it also makes it more brittle, and prone to
heat shock. If they marketed it just for gold and silver, it
would probably be OK. but they market those things for platinum
use too, and at those temps, though the block takes the heat
without undue melting, it often cracks from uneven heating from
one part of the block to another. Plus, the high degree of
sintering makes the things very good heat conductors for a
ceramic. Wanna guess what that does to those rubber feet you so
like? My personal opinion of those rubber feet is not
completely printable. And I’d guess the engineer or whomever
decided to put them on is not someone who has ever seriously used
a torch with one of those blocks. You don’t need to be heating
the corner. with a six by six inch block, withing an hours worth
of platinum work in the center of the block, the rubber feet had
completely melted, making a ghod-awful mess of the bench, which
of course was also now starting to scorch nicely. If you take
off the rubber feet, and use a suitible solvent to clean off the
remaining glue, you can then use these blocks on a piece of
transite board underneath to protect the benchtop. THAT, at
least works. Until the block cracks that is. After I broke the
second one in thirds with a platinum soldering job within six
months of buying the first one, i’ve not gone back to these
blocks.
What I use now is a bit unusual. I’d really like to be using
the blocks made by wesgo, makers of the platinum melting dishes
and crucibles. Similar to your soldering blocks listed above,
but less highly sintered, and therefor slightly better insulated,
and a LOT less brittle and prone to cracking. (A much better
product, IMHO) but at something like forty bucks each, they’re
way too expensive for my poor blood, especially when I can
scrounge something just as good for almost free…
Until a couple years ago, I worked for a firm that did a good
deal of platinum casting. They’d upgraded to an induction melt
machine, and no longer had a use for the large box of mostly
cracked and flawed wesgo casting crucibles in the back. Those
crucibles don’t last forever before cracking here or there, but
the cracks are usually in the top “cover” part of the form, not
the base. So I set up a couple of those crucibles on a lapidary
slab saw and sliced off the bottoms. Left me with a pad slightly
thinner than the one wesgo sells actually as a pad, and it’s got
a slight hollow in one side. But other than that, it makes a
great little solder pad. I cut off several of them this way,
and I’ve yet to break or crack even one of em. I do use them on
a surface I won’t be burning, such as the solder pad that comes
on my benchmate soldering station.
Also, if you use these for platinum, DONT use them also for
gold. The reason is not the possible contamination of the
platinum by the gold. THAT is easy to avoid if you’ve got eyes
that work OK. The problem is that working with gold or silver,
we use varius fluxes. And those fluxes, as well as boric acid,
will get on the solder pad. When that is then heated to the
melting temp of platinum or platinum solders, those fluxes will
attack the solder pad a bit, changing the surface composition to
a mix of the flux componants and the solder pad componants. The
result is a glass that melts a fair bit lower than the pad
itself, and will then stick to your platinum if you let it.
But, it won’t come off nicely in the pickle. quite a pain in the
rear to then clean off. So if you work platinum, either with a
wesgo pad, crucible, or the above mentioned solder pads, reserve
a CLEAN one for use exclusively with platinum, and don’t get flux
or boric acid on that pad.
Peter Rowe