chemistry of spackling powder

Greetings,

I'm putting this post here, as I don't see a specific "support material" section. This should be a simple question to answer, but both memory and Google fail me: is spackling compound reusable? Or, to put it in more precise words, does spackling compound (Polyfiller for some, Polyfilla for others) undergo any non-reversible chemical changes with the addition of water?

What I'm trying to do here is determine whether such a material could be used as a support material (which I've read it can), washed out of a printed part, and then through simply collecting the wash water, evaporation, and possibly grinding, have the same material you started with? A plastic analogy would be a simple thermoplastic - shape it, collect it, melt it, re-shape it.

Thanks.

I'm putting this post here, as I don't see a specific "support material" section.

About 80% of the chatter here should go in:
http://reprap.org/pipermail/reprap-dev/
our official friendly-but-technical mailing list for all you officially frendly-but-technical people out there.
(You have to join, Nether10, it's compulsory. )

The other 20% should go into mediawiki talk pages. (We should never have installed forum software if we were going to use a mediawiki.)

btw, we're probably going to swap in something new for the mediawiki soon:
http://lists.reprap.org/mailman/listinfo/library-gnomes
If you're curious, hop in. If you know perl or django, especially hop in.

This should be a simple question to answer, but both memory and Google fail me: is spackling compound reusable? Or, to put it in more precise words, does spackling compound (Polyfiller for some, Polyfilla for others) undergo any non-reversible chemical changes with the addition of water?

Yes. It is probably plaster of paris plus additives:
http://en.wikipedia.org/wiki/Plaster

"When the dry plaster powder is mixed with water, it re-forms into gypsum." You'd have to heat it to 300C to drive the water out and turn the gypsum back into dry plaster.

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-Sebastien, RepRap.org library gnome.

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