Here’s one that shows that you really can’t ever know it all…
I’m a fan of the “Practical Goldsmith” series of books out of
Germany. Those are the white ones that are half German, half English.
There are a bunch of them on various topics, and they show
step-by-step examples of various techniques. I find them useful
because they show the German/continental take on the techniques, as
opposed to the American and English procedures that I learned.
Always interesting to see another way of doing things. (Although it’d
be nice if they had an English speaking jeweler clean up the English
terminology. It’s very clear that their translator is a native German
speaker who doesn’t know English jewelry terms.)
Which leads to my question: in leafing through volume 13, the one on
granulation and niello, there’s a little throw-away reference to
’swirled casting channels, as their turned forms lead to a pore free
cast’. It shows a picture of a cast buckle with a pair of sprues
that look like they were made up out of rectangular wax wire,
(?4x1mm?) that was twisted into a shape resembling a candy-cane, or
spiral wire. (Top right picture on Pg 54, for those of you who have
the book.) The section’s on Niello, so there’s no amplification of
the comment, it’s just a little caption for one picture.
According to everything I know about casting, I’d think they’d both
add turbulence to the flow, as well as causing the sprues to cool
too quickly, since you’re bleeding heat into the walls as the metal
swirls past them. They’re not as thick as a round sprue either, so
they’ll freeze before a round sprue would have. I’d think that’d make
porosity worse, not better.
Anybody have any experience with spiraled sprues? Do they actually
I’m going to do a few, just to see what happens, but with a
centrifuge, you can get away with murder, at least at a small scale,
so it’ll be difficult to figure out if they’re making things better