[Burningkrome]

I do some precious metal casting as a hobby. I was looking into ways to make more resilient temporary molds with more thermal conductivity and stumbled across a paper where 12-20% aluminum powder was added to plaster. However, upon further googling, I also came up with youtube vids of people mixing aluminum powder and plaster to make thermite.

These seem extraordinarily out of sync with each other So, which is it? Does the 'thermite' have to be in powder form in order to be explosive...and once its been cast into a solid plaster (like a mold) it is no longer flammable?

[Arkcon]

The simplest answer is no.  Thermite isn't made of aluminum powder and plaster.   Recheck your sources, and see what you need to work with.

[Burningkrome]

Well, I don't think it was actually "thermite". Just a flammable substance that behaved like a poor mans thermite (hot, bright, extended burn). As I understand it, it has to do with the endothermic reaction between CaSO4 and Al (or AlO2).

[billnotgatez]

...
I was looking into ways to make more resilient temporary molds with more thermal conductivity and stumbled across a paper where 12-20% aluminum powder was added to plaster.
...

I have not looked this up to make sure but
I think you mean
alumina powder which is aluminium(III) oxide powder
and not
aluminum powder.

Alumina is used in ceramics as a refractory.
See
https://en.wikipedia.org/wiki/Aluminium_oxide

Although, I work mostly in ceramics,
I have done precious metal clay as well and would like the link to the paper you mention.

[billnotgatez]

...  (or AlO2).

Not sure what you meant.