Home made sand mullers for casting

[BillKnighton]

I've been messing with petrobond blended sand for sandcasting parts and have run out of fresh sand. It gets charred and needs to be remixed. I can only do a small amount by hand and what I've read is that to go through a usable amount and especially to mix petrobond into new sand, a muller is required. Does anyone on here do this and have pics of their setup? There are some on youtube and links on Artmetal, but I'd like to see more before getting too far into making something.

[J.B. Castagnos]

I mixed some using a paint mixer in a drill, did a decent job. I don't remember the measurements, but when I added the liquid to the sand and started mixing it didn't appear to be near enough. After mixing a while it blended in. If you could find a paint shaker you could mix two gallon cans at a time, best to leave some space for mixing. I 've seen older ones at the automotive paint stores when they are updated.

[Benjamin Roth]

Stephen Chastain has a new book on building a muller:

http://stephenchastain.com/book8.html

To recondition your sand without a muller you can clean an area of concrete and spread out some of the petrobond. Add some 10 Weight Non-Detergent oil and use a trowel to mix and pack it together. There needs to be pressure created in order to completely coat all of the sand grains. It takes a lot of time and is very labor intensive so it works best will small amounts.

The burned sand alongside the casting should be discarded and not reused. I have been reusing some of it but the sand will work better for longer if you do not use it.

Yes you do have to use a muller in order to make a proper mix. If you do not the sand will not have a high enough strength and there will be molding problems, collapsing molds, or even deformed castings from the pressure of the metal. I have picked up my petrobond from foundries and for a small fee they may even mix it for you.

Benjamin

[Doug E.]

Bill,

I borrowed a small commercial muller when I was casting. I want to say it was a "speedy muller", but not sure that was the brand. I have photos somewhere. It was about 18" in dia by a foot high, but mulled sand quicker than I could ram the flasks up.

Benjamin,

I set the burned sand aside and added more binder (as well as oil) when I mulled it. Worked great.

Regards,

Doug.