Re: Lost Foam casting inquiry


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Posted by Sander Rosenberg on October 28, 1999 at 21:20:20:

In Reply to: Re: Lost Foam casting inquiry posted by bruce paul fink on October 27, 1999 at 19:52:25:

Re: Lost foam inquiry

Bruce Paul,

Well, I've spent the last period of days quite obsessing over this lost foam business. We did a pour on Sunday, so I prepared a test of sorts.

I used the same torso form as before, cast in urethane foam with a loose sand core. I had found a American Foundrymen's Assn. workbook about gating systems, so I made a system which incorporated some of those recommended features but, unfortunately, I accidentally "choked" the flow right where the gates entered the form, which was only partially cast. The gating system came out superbly though! I minimized venting

since I wanted to isolate the experiment. I DO think that venting in loose sand is a redundancy with syrofoam, as far as gases are concerned. Other justifications FOR venting might include the channeling of smoke away from the pouring cup for visibility, as well as a signal of the mold being filled, though.

Call it a learning experience, but one important thing was that the one part of the gating system that wasn't (low-med. density) styrofoam was a cast urethane resevoir well (at the bottom of the sprue) which exhibited the same sort of surface defects that I encountered before (and which I sent you a jpg of on the torso). I have heard that urethane is not an ideal material for lost foam, so now I am thinking that I should see if I can find a lower density urethane to see if that helps. I don't believe there is a way to cast styrene foam (itself); it doesn't seem to

be available as a two-part or propellant-charged can as is urethane,

only as styrene beads which must be steamed to expand (which would wreck any rubber mold I might be using). So far I think that styrofoam is pretty easy to direct cast to metal, but I really want to find a foam which I can cast into a form while it is still liquid/soft.

Today I found some latex foam that I will play with. I've even considered meringue! Hell, they use jello in casting, don't they?

Well, in a coupla weeks we're gonna pour bronze, so I'll see what I can do with that. I've cast small figures in that using stryrofoam with no problem...

I really appreciated all your comments (and humour!). I don't think you're an old fart at all! (Except in the honorific sense, of course).

And I'm very impressed with what I've seen of your work on your page. I love nature, and birds in particular, but I find that much art which tries to represent that some appears corny, but you've managed to circumvent that. Some of it has what I might describe as an Art Nouveau feel which is very lovely indeed!

Anyway, I'm going to try to stop obessing about this foam stuff for a week or so, and tend to some OTHER projects I've been neglecting!

Take care!

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