So we all endeavor to make our models as hollow as possible to reduce to cost of 3D printing. But when you get your model in your hand, it is usually light as a feather and has no 'substance' to it. So I have ben pondering filling the void inside the model with something to make it a solid mass: (Theory: Drill a little hole in an inconspicuous spot, fill, and seal.) I'm posting this to get some ideas from the masses as I am sure I am not the first to think about this. Some ideas I've come up with are: Epoxy: Mixing enough of it could be a little pricey and I am not sure if there would be a chemical reaction with the model's medium. 5 minute epoxy would add some serious strength to the model. Sand: Ya, regular old sand. Where I live I have access to the ocean and a seemingly inexhaustable supply of sand. I like the idea of how much weight this would add to the model, but think it might be near impossible to fill all the void inside. Big con here is that the Sand does not add any strength to the model. Plaster of Paris: Major concern here is that I know POP can get pretty hot when it cures, so the melting point of the model's medium wold be a concern. Otherwise, a decent choice. Wax: I'm sure the melting point of wax is far lower than the Model's medium, but since heat is involved here, it bears consideration. Resin: Dozens of choices here, but all of them extremely sticky potential mess. Curing time would also be a concern. Glue: Chemical reactions with the Model's medium would be a concern with many types of glues. And the curing time might make others a bad solution. But I'm sure there is a glue out there that might fit the bill. I'm looking for feedback, other ideas, advice, words of wisdom, experience, etc, etc. anyone out there already done something like this?