What if you double stacked the cups nesting doll style so the negative space was slightly larger for flow, and or maybe leave them to soaked instead of pouring the acetone in?

* 2 small vent columns next to sprue * cook out the foam residue * preheat the mold Ps: you can dribble sand on mold after each layer (after first few layers) to make mold stronger for above 2 steps

You have a couple of issues with the aluminum pour. Fluidity is one. Use a better alloy helps a lot. I don't remember is you said what kind of aluminum you used. It matters for thin casting. Another thing that helps fluidity is a higher pour temperature. The other issue was panic. Your start, stop, and restart in the pour made things worse. You used the word porosity but that wasn't porosity, more like cold shunts and early solidification. As far as your pouring technique. Stop dribbling aluminum into your mold. You need a nice continuous stream.

I'm commenting in the middle of the video, but you had to know that waiting 10 seconds before pouring again means you're not going to get fusion and have a bunch of cold shuts. Remember black sooty smoke is a mold release for a reason.. and your first pour is covered with it. The way you did the acetone didn't get rid of the styrofoam. I'd say probably 90% of it is still IN the mold. You just turned it from expanded foam, into solid hard plastic at the lowest level or underhang by the sprue. Solid, dense plastic that will happily burn and outgas for a long time, because of low surface area:mass ratio (as a solid). Had you poured this without the acetone, it probably would have worked just fine! I've done lost foam casting a few times, and yea.. acetone method is the worst way to go about it. You get solid chunks of styrene in random places, coat the internal surfaces in a thin layer of plastic, etc. Either just pour the metal HOT right into the styrofoam, or burn it out before hand. I'm sure there's a way to make it work, with a vent/drain at the bottom, and large quantities of acetone, so the styrene has a way to flow out of the mold completely. Or just pour hot without interruptions straight onto the foam. Solid styrene (from acetone on styrofoam) turns into a hard, brittle, glass-like plastic that's fairly dense.

Hm I wonder if having cup point upwards and pour on outside route, turning around into bottom of air to fill cup, cop top having air holes so metal can rise. Not too sure how well that would work.

This is what I was going to suggest. When you melted the styrofoam, you created solid plastic in areas. You could see that in the casting attempt. If you were to burn out all of the styrofoam, not only would it all vaporize as a gas, but it would preheat the mold for when you pour into it.

The problem is, he used Drywall Compound, which is gypsum dust mixed with water. It doesn't do well in extreme heat, so burning it or heating it in a oven, would reduce it back to gypsum

I was likewise thinking that heating the moulds to burn out the foam would work well, even more so if you used plaster built in layers very thin mix at first then gradually thicker coats in layers. Add in increasing amounts of silica sand then when estimated about three to five millimeters thick. Just heat in the casting furnace to burn em out. Then do not let them cool before the pour. Pour the aluminum while the moulds are still glowing hot. The heat of the moulds will help the metal to stay flowable until the temperature drops to freeze it in shape. After that it's just dunk in water to cool even more and get the moulds to crack from the temp swing shock.

@@KrazyMitchAdventures hence why I said plaster, as shortened for plaster of Paris. Gypsum while it does contain some likeness to plaster of Paris, it is not the same as. I know how to cast using plaster embedded with silica dust and sand at very high temps, that when quenched the plaster crumbles into a slurry in the quench water. It's a fantastically interesting process and very dangerous to do if you are not wearing protection, since the risk of splash burns is quite high when the just off incandescent mould and metal hits even rolling boil quench water there is quite a bit of stream and lots of popping taking place. So if you do it, be extremely careful and don't stand right on the quench. Long grippers are a very handy tool for that kind of stuff.

@@KrazyMitchAdventures That's true. He would need to use the suspendaslurry stuff.

And there is no gas vent so all the gas is trying to go up,from which you pour metal .And thats why it had so much porosity . Pouring basin and sprue are a joke.

kilning them would get rid of any residual styrofoam/acetone slurry as well

This is something companies actually do.

I was actually thinking that he could do as u mentioned. This would help to take out the poli styrene from the mould but again you would possibly need to be careful about the mould cracking in the heat cycle but it could help to stop the water from the joint compound from boiling so quickly with the water then also causing problems with the mould filling up easily because of the small thickness of the cups same thing really as lost pla if you don't get rid of the pla you have a lot of issues with the mould filling even

It does look like cold lap, something that I have experience of when the metal is too cold when poured, however if the metal is too hot, it's so runny it runs into the sand an you get a sandy casting ( like a casting, but with a metal/sand skin )- not good when zirconia sand is used, it blunts carbide tools like you wouldn't believe.

lean cup

Good Idea, I was thinking that he might do that.

A bottom fed casting would be even better, allowing the gases to exit through the riser instead of flowing against the flow of metal. On some small castings, spikes are poked through the sand to touch the pattern to give a path for gasses to vent out, and the resulting metal that enters the vent can be easily snapped off.

@@joejoejoejoejoejoe4391 I cast bronze coins and thats the method. I use a flat two-part sand mold. Metal goes in one edge of the coin, and I have 2 small air vents at 1/3 and 2/3 position going up. That way, the metal can flow in and push any gases up and out the vents as it flows. It also helps when you're casting things like animals, flat, that have four legs and a tail. Put an air vent at each extremity or it won't fill completely. Those extra small "sprues" are easy enough to cut off.

Lol Thank you!

Might sound weird, but Id like to see that process.

They are!

Probably. The sand etc is what handles most of the heat.