On Sat, 01 Nov 2008 11:07:44 -0500, Tim Wescott
wrote:

Do you know of any references on how to do it right? I've got a project
in mind (that probably needs to wait 10 years) that could be done quite
well with plaster cast aluminum, I think.
=================
One of the slickest things I have see for low volume use is lost
foam with "plaster" investment. Make the model out of styrafoam,
cost with plaster, possibly support the plaster mold in a flask
with sand, and pour. Styrafoam will flash off [don't breath the
very thick black smoke that will be generated -- will make a mess
if you do this indoors as the soot will coat whatever the smoke
comes in contact with]

As other posters have noted this is not "patching plaster" but
investment or refactory plaster. Any water or even dampness is a
NONO. FWIW -- you can make a concrete floor "explode" if you
dump a ladel/crucible of hot metal on it.

do a google search on "investment casting" or "plaster casting"
Several home/hobby news groups and websites active.

also google on "home metal foundry"

You can "paint" the styrafoam to seal the pores for even finer
finish.

http://www.theworkshop.ca/casting/fo...oamcasting.htm
http://www.metalcastingzone.com/lost...asting-videos/
http://www.prlog.org/10078409-castin...-released.html
http://www.prlog.org/10074778-metal-...ting-zone.html

If you use sand I suggest oil sand and not green [water damp]
sand. Petrobond is the buzzword for oil molding sand.

take a look at the casting books from Lindsay's books.
http://lindsaybks.com/prod/sub/foundry.html
Be reminded that Lindsey specalizes in reprints, so while the
information you get will be valid, it may not be up todate.
Chastain's books are all very good.