Well, the results of the latex were by far superior for about a day and half, after that it begins to shrink unmercifully, my rather large fat mans arm kinda turned into a 12 year old anorexic arm.
So here’s the processes i tried,
Firstly alginate is definitely the way to go for the mould, accept no substitutes,
What to do with the mould after that is a bit controversial, the recommended route would be to use a certain grade of silicone that needs a second chemical to set it, can;t remember the names right now, but they are very expensive and i could only find them on the internet, I personally didn’t go down that route to try to keep costs down.
so i tried the cheap route, builders silicone, works fantastically but there was two major flaws with it,
1, its not fluid enough to get into the nooks and crannies of the mould, namely the fingers, level of detail was great on the texture of the skin though,
2, It stinks to high heaven, Jesus make sure you wear a protective mask when building and and when handling it for the rest of your life.
Next route was the liquid latex,
this is the one i ended up going with, but remember the scale issue.
Firstly make your mould, and pour the liquid latex in and swish it about into all the nooks and crannies, leave it set, this will be a micro thin layer and not very usable, you can use a hairdryer to set the latex faster takes about 15min to set.
Then repeat the process until you build up a layer about 2mm thick. you can add a compound to the latex after this which makes it thicker but takes longer to set mix up your latex and pour into the mould nice n thick about another 2 mm thick. leave it set for a few days just to be sure.
So what you should have now is a hollowed out arm stuck in a mould, recommendation, mix up another batch of alginate and fill the hole in, takes about 5 mins to set. break the original casing mould and your left with a floppy arm that you can smack someone across the face with!
Looks great for a day or two but starts to shrink after that, gets smaller and browner the more the latex fully dries out.
hope this helps, ill stick a foto of the arm up online in the next day or so, but remember the shrinkage.