I'd like to use something like this:
https://www.amazon.co.uk/Baby-Chromatic-Alginate-Moulding-Powder/dp/B071GPRGDF
To cold cast some body parts with metal powder.

What would be the best resin/epoxy etc to use?

Thanks!

Keep in mind that alginate is a water based product, and is actually only useable for a couple of hours while it is still very wet. Theres a lot of resins that wont like being poured into that, especially polyurethanes. Epoxies might cope, but depends on the specific epoxy, theres a good chance they will absorb water and come out very milky. 


The ideal solution is to use a skin safe silicone instead of the alginate, but this will be significantly more expensive, especially for a one off project.