F. George McDuffee wrote:
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.



Petrobond has resin within for fine smooth edges. It flows and
fills in the sides as the metal flows and fills the design.

Martin