nothing i'll say below is 100% sure, it's just my guesses. I personally had great success using basic plaster for casting my last and then just dying some more plaster with food colouring for building on my cast, it's quite useful to differenciate your actual foot fro the additionnal matter you add to create the last shape, espacially when you dont want to sand off too much. So i guess thats what he does in the video. For the final cast, he said in an other comment it's an orthopedic expanding resin, but he can't give any ling because it's from a profesionnal shop. Usually, othopedic supply shops sell some rigid expanding polyurthane resin/foam with a very high density (about 400kg/m³). Unfotunately those shops sell only to licenced professionnals, so you'll have to find a friend that is willing to buy that for you. If you can't, you can look for rigid high density PU foam with similac caracteristics, but not labeled for this purpose. It's hard to find gigid foams with a density of 400kg/m, but you can find some with about 300kg/m density (for reference, you can start sticking nails and screws starting from 200km/m3 density, so i wouldn't go lower.) from france, here some websites (profesionnal and retail) if found selling those products. Pro : www.neut.fr/fr/materiaux-podo-orthese/product/mousse-polyurethane-expansee-composant-a.html www.e-podiatech.com/fr/accessoires-ateliers/199-632-podiarigide-expansee-pu-element-a.html#/202-bidon-1_kg Retail : feroca.com/fr/mousses-de-polyurethane/617-1352-easyfoam-300-mousse-rigide-de-polyurethane.html#/217-capacite_kits-kit_de_2_kg I dived into this subject a lot the past week, and i ordered the foam on the last link i put above (the feroca website). In about one to three weeks from now, i'll report to you if my attempt with the product was successful. For the black sealant, i'm less sure about what it is it but it's probably the release agent for the PU foam, so it's not really important which it is. It' could be some liquid release wax (which often comes in black), or a spray realease, that is found easily in crafts supply stores.