I see everyone seems to use solid pouring cups and then melt out before casting. If hollow ones would be better they are simple to make.. I came up with this idea because I wanted a small bowel for a sterling brandy snifter. It amounts to filling a balloon with enough water to get the shape you want.. Pop it in the fridge to chill it down, a light spray with silicone before dipping... I've never had one break, but I did double balloon the big one. If you keep chilling and dipping you can get 1/8 walls. Just pop the balloon to get it out
I recently started 3D printing mine in PLA and then sealing the open end over with a thin wax cover, before I started the investment process. The wax melts out very quickly or you can melt it out with plumber's torch. and then the PLA pouring cup is very thin so it burns out very quickly. The advantage I see is you can superglue the PLA 3D printed cup to your PLA pattern. Guess its not a lot of help for the wax only pattern makers. BUT! I made a 2 piece PLA mold for my sprues and pouring cups that I can fill with wax, let cool and then separate. With the wax sprue pour cup I melt it with a flame and attach it to my wax patterns before investing.
I've used Styrofoam cups, capped with cardboard and coated with wax. Its an idea that I picked up from LunarBurn videos.
I'm an analog man adrift in a digital world.. Although I do admire the use of tools that can be told exactly what to do.. They give a determined craftsman a way to compete and excel. My career was with mostly hand tools, and a tiny torch. . 50 years ago, to tool at the top of my list was a two sided hydraulic rolling mill.. Here's a few things in sterling that I did 30 years ago, using an alcohol lamp and a couple dental tools. And a Fordom to do the knife handle.. There's an emerald in the knife handle, and a ruby in the horse eye. I cut and polished the Lapis, then built the ring to fit it.. I still have hundreds of vulcanized rubber molds that I've made over the years. Sometimes used as a starting point as a base for the new piece... The elephants are the originals for molds for links in a linked bracelet. The cut link is where the box catch is built into after casting