I’ve started casting some small buckles out of bronze using the sand
casting method. I seem to be getting tiny “craters” in the surface.
I’m guessing these are gas bubbles of some sort. The bronze is a
silicon bronze (Oster D). Any ideas?
If it’s a water bond sand, it may be a bit too wet. If it’s an oil
bond, or delft “clay”, what may be happening is that loose sand is
getting knocked into the impression when you pour your material in.
You may simply need to pack your frame a little more robustly, and
use a tube to blow any loose bits from cutting your vents and gates
away.
It seams that your bronze is degassing after pouring. Try to ad
before you cast a small amount of aluminum in the smelt. And stir
this and extra gasses will burn out. You bronze will cast better.
Other problem can be your sand is to moist.
Greetings,
Martin Niemeijer
N design
Cultuurwerkplaats R10
Rieteweg 10
8041 AK Zwolle
The Netherlands
info@ndesign.nl ; www.ndesign.nl
What kind of sand are you using? What temperature is the bronze
when poured? Are you using a clean crucible? Are you venting your
wand work? Can you take a picture or the pits and send it to me?
Is the metal new or scrap or used?