Re: [NOOB] How much is needed make a mold and cast two copies of a Stormtrooper helme
Well you can do everything with materials from smooth on, which is a great company to buy from when you're just starting out as they have a ton of videos about using their products.
For the mould, you can expect to use 5 of their trial size kits of silicone, rebound 25 is a good one at about $30 per kit. Look at their videos of making a brushable mould. You'll need a mother mould to keep it rigid while you're casting, I use fibreglass but they do something called plasti-paste that will work. Probably a couple of the trial kits at $35 each. Once the mould is done, you need casting materials, I don't remember which of their resins are best for slush casting, you can call them and ask. Probably 3 of their trial kits ($30 each) to make two helmets? You might be able to do one kit per helmet if you don't make any mistakes.
You'll need a dremel or something similar to trim and sand the helmet when it comes out of the mould, and then all the parts to actually finish the helmet, not to mention paint.
So assuming you don't need to buy a dremel, then like I said, figure about $300 to make two helmets minimum, not including the cost of the donor helmet that may or may not survive the moulding process completely unscathed. I just looked up the helmets, they're $75 each on amazon. If you were planning to mod the helmet to a much higher degree of accuracy then it might be a fun project, otherwise I'd say just buy 3 helmets from the start.
Of course there are other materials out there, but me being in the UK I don't know if anything I recommend beyond the Smooth On stuff will actually be available. Fibreglass is always cheap but not something to recommend to a novice.
So there you go, I don't mean to pour cold water over your ambitions but if your plan is to get an extra couple of helmets cheaper than just buying them outright, then you're in for a shock when you total everything up.
And finally like others have said, this doesn't even get into the ethics of whether it's the right thing to do. I've listed everything here that you would need to do it mainly so you can see that sometimes it's easier just to buy something. What you go on and do with this info is down to you.