Hi Dave et al,
I get them at a local brickyard. There, they're called
'silversmiths bricks'. They're 2 1/2" x 4 1/2" x 9" & weigh 1# 14
oz. They're soft enough that pins can be pushed in with your
fingers. While they're smooth, they have many holes that may be the
result of small air bubbles trapped when the bricks were cast.
I've been buying "magnesia" blocks from various suppliers for years
and over the years, the composition has changed so that they're no
longer as soft as they were at one time. For the kind of soldering I
do most often, I need to be able to push bezel cups into the block so
that I can solder from the back.
A few years ago, when I noticed that the (seemingly the same) blocks
had become too hard to push bezels into, I did a lot of research and
discovered that there is just one manufacturer of all the "magnesia"
blocks sold by jewelry equipment suppliers and that I was therefore
out of luck trying to order the older, softer ones.
Since then, I have tried every other soldering substance shown in
every catalog I can get my hands on, and some that are not even shown
in catalogs. I've found a few substances that come close but there's
something wrong with each one. If I hadn't casually thrown out
partially-used blocks many years ago, I'd probably have a life-time
supply but, as it is, I have only about 4 of the old blocks left and
eventually I'll have sanded the surfaces down so much that they'll
It sounds as if, perhaps (crossing all her fingers), you have found
something different, Dave, and I would love to try it. I'm out of
town at the moment and will check brickyards when I get back to LA
but I have a feeling this isn't a common item for brickyards to
stock. If you can give me any additional that may help
me locate these blocks or the manufacturer, I would be most grateful.
And if anyone else has another suggestion, I would love to hear it.
(I should note that using investment to stabilize parts is
impractical for my purposes.)
Beth (with only 2 days left in Australia before the 15 hour flight
back home )