i was thinking of melting aluminum and making aluminum plates but what would i use as a mold? could i use a cookie sheet(with sides lol)or would i have to make a mold?

For your safety, no cookie sheets. Molten metal can be a safety concern. I recommend sand-casting with a two-part upper and lower mold using foundry sand, and not taking any shortcuts on safety.

just wondering but y can u not use a cookie sheet? just wondering and i cant sand cast i don't have the sand or a 2 part mold

Molten metal is pretty dangerous. Spatter is a bad thing. Using a mold helps keep things contained and safe.

Hopefully, someone with more expertise on casting can explain it better.

You can get sand and make a two part mold it is harder to regrow tissues

so far i have been using a cupcake tin to make ingots wouldn't it be the same as that? oh and i always preheat it a bit over my forge before pouring

buddy, read your private messages

just asking to let u know not trying to argue but could you use one?

theres nothing new there?

Saftey aside, a cookie sheet wouldn't give you the best results. you would need a 2 part mold with a sprue and a runner to account for shrinkage which you would see alot of in the center of the plate if you just used a cookie sheet.

If you preheat the sheets there should be no problems with moisture or anything.
However, the sheet will most likely flex and deform and you won't be even close to a flat plate. Aluminum has too much surface tension to settle flat in an open mold as is evident by any ingots you have made being somewhat bubbled over. A big reason you use closed molds when making actual items.

Getting set up with green sand is fairly easy. Lost foam is a very cheap starter way to make items for the cost of a bag of sand. I don't think you will get the results you are looking for though without a little investment.

Believe it or not a hole in the ground can suffice as a mold, again most likely with unsatisfactory results. That's how pig iron got its name. The open molds cut in the sand at the base of the furnace resembled a mother pig and suckling piglets

When they say hole in the ground, it's not just a pit someone dug. More than likely an explosive splattering of molten aluminum would occur. Any moisture would cause an instant steam explosion. Those pig iron molds were done with very dry sand because of the heat of the giant furnaces being on well before the pour.

For safety and speed, just go to your local metal dealer and buy some aluminum plate. You will get exactly what you want in the size you want very easily and safely. You can usually get remnant pieces of aluminum for less than $2 pound. I've even gotten it on sale for < $1 pound.

I'm with azIRonSmith. It'd probably be better all round to buy some aluminum plate and save your Al scraps for other castings.

buddy, i recommend backyard metalcasting for these questions. you will find people that know a lot about these things there.