Recommended casting material?

[RedbirdXlll]

Hello, I'm an amateur prop builder just starting out my (hopefully) long career with some replica commissions.

I'd like to make a mold and cast the replica I'm currently working on (Fili's twin swords) so that I only have to fabricate one of them and can also offer other people casts to help offset the initial costs. But these swords are pretty solid (27" long and at least 4" thick in places) and I'm worried that something like resin will be too heavy to carry around at a con (which is what these swords are for).

I'm not sure what other materials would be a good option for this project, so I'm asking you guys: do you have any preferred, light weight casting material for large props? Or do you think fabricating two swords by hand is the better option at this point?

Any advice you can offer would be great!

This is what the sword looks like, for those of you who don't know:

 

[robn1]

I've never made anything like that, but a light weight resin or foam is probably best. I'd go with rigid foam.
http://www.reynoldsam.com/product/foam/

http://www.reynoldsam.com/product/feather-lite/

 

[Darksyde13]

What kind of mold are you planning to make? As for casting the only lighter weight material that springs to mind is expanding foam as mentioned. I recommend a 'self skinning' foam product to save you some on finishing work/prep work. You can also try your hand at 'slush' casting a hollow blade with resin and then either leaving it hollow or mixing in the expanding foam to finish off the inside. This will require some more work/planning for your actual mold though.

PS: These guys have some grate tutorial videos and were the first people I came across that used some pre-painting techniqes that look to cut down on painting time considerably. https://www.youtube.com/watch?v=1PIsKtu9R08

 

[robstyle]

the most basic and cheapest route is going to be fiberglass. Its tried and true. Rubber or rubber/plastic hybrid materials are well out of the price range and for well advanced users.

 

[cavx]

I agree 100%. Fibre-glass (even when you buy a kit off a home hardware store) is still "affordable" and will have the highest strength to weight ratio of any building materials for this project.

 

[swgeek]

Fiberglass is good. You could also use a skin of urethane resin and back it with 2 part foam. Pour enough resin in to give your prop a thin skin, tumble the mold around until the whole thing is coated (it might take a couple pours). Then once the resin sets up, pour in A/B foam, let that set, then demold.

 

[RedbirdXlll]

[UPDATE]

I finished these swords! Thank you so much for all of your suggestions - I will definitely keep them in mind for future projects!

You can check out my whole build process here: http://www.therpf.com/showthread.php?t=247989