Bronze problems

Jeff_mack 2004-03-10 05:12:59 UTC #1

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?

Thanks!
Jeff

Ron_Charlotte1 2004-03-11 10:56:27 UTC #2

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.

Ron Charlotte – Gainesville, FL
@Ron_Charlotte1 OR afn03234@afn.org

martin_Niemeijer4 2004-03-11 11:30:46 UTC #3

Hello Jeff,

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

John4 2004-03-11 11:30:48 UTC #4

Jeff,

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?

Need this info to get started.
John Dach

Jeff_mack 2004-03-13 01:49:44 UTC #5

What kind of sand are you using?

It’s premixed casting sand. I think I bought it from Thunderbird
Jewelry Supply.

What temperature is the bronze when poured?

Not sure. I don’t have an immersion pyrometer. I waited until it
looked like a nice little lake of molten bronze, fluxed, then pored.

Are you using a clean crucible?

It’s nearly brand new, and has only ben used for bronze.

Are you venting your wand work?

I guess not. How do I do that?

Can you take a picture or the pits and send it to me?

I’ll try to cast something and take another pic this weekend. I
ground and polished the last piece.

Is the metal new or scrap or used?

New Oster Bronze D from Contenti.

Thanks!
Jeff