Thread: Molding and casting polyurethane foam bones

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I'm currently in the process of making an severed hand/arm prop so thought i would post a couple of tutorials on how i do it. This tutorial shows how to make polyurethane bones which stick out of the hand.

You will need:
rigid polyurethane foam (500g is more than enough)
http://cgi.ebay.co.uk/LD40-Rigid-Pol...c#ht_656wt_905
300g RTV silicone ( may need more depending on size of mold box)
stir/lollipop sticks
clay, water or oil based should both be fine
mold straps (elastic bands)
mold box (yogurt pot)
super glue
scalpel or sharp knife

Step 1
you first need to decide on how big you want your bones to be, then you can make these from clay. Remember, the bigger the bone, the bigger the mold box, the more silicone is needed.


step 2
Using super glue, secure your bone to the bottom of the mold box, this stops it from falling over and rising to the top when the silicone is poured in.


Step 3
Pour the silicone over the clay bone, make sure it goes above the bone. Wait until the silicone has fully set and cut the mold box apart, you must cut the mold box because we super glued the clay bone to it before. Using the scalpel cut the mold in half and remove the clay bone, It helps if you cut the silicone in a wavy line as it allows the two pieces to rejoin later on.


Step 4
Using elastic bands or proper mold straps, put the two silicone pieces back together. Prior to this you will need to apply a mold release such as baby oil or talc.


Step 5
Measure out equal parts of A and B, for a casting this size half a bottle cap of each is a good amount. Mix A and B together for a maximum of 10 seconds and pour it into the mold. The foam will begin to expand immediately,after about 5 minutes the foam should be hard enough for you to remove the straps and carefully pull the 2 piece mold apart. You can now remove your foam bone.


So that's it....
It's fairly cheap and very easy to do, also the amount of bones you can make from just 500g of foam is rather alot. The silicone is the most expensive part of this process, but it should last for years.
Of course if your not wanting to make bones for a severed hand, you could just
use the same technique but on a larger scale to make bones for a homemade skeleton.
I will update this post at a later date to show how you can paint and seal the bones.

For better quality bones you could use Easyflo 60 casting resin, this would remove the amount of air bubbles seen in the foam.

Please feel free to ask any questions or make comments
Thanks for looking
Phil

Nice! Can't wait for updates.

That's a really good tutorial! Thanks very much for posting it. I just might try this this year!

Thanks for the kind comments Mordessa and Crunch,
I'm gonna try casting some Easyflo 60 bones, i don't know why i didn't think of doing that in the first place, but the foam is alot cheaper than Easyflo 60.
Thanks
Phil

Great tutorial! Does anyone know of a GOOD 2-part polyurethane foam that's more dense?

Sorry Eyegore this is the only type of PU foam I've used, and I'm not aware of a denser PU foam. Also I'm very sorry about the delay with the painting update, I've decided to skip this step because the silicone i use is slow setting and it hard to keep the foam bones in place, so im scrapping the bones altogether , perhaps i will do one in the future when i can afford some better, faster setting silicone such as Platsil Gel-10. Watch Out for an update on painting the silicone hand.
Thanks
Phil

Ok guys I'm gonna try and explain how i painted the silicone hand, it was real simple but i'm happy with the results. Unfortunately, it's rather hard to take photographs of what your doing whilst covered in silicone, so this will be a written explanation.

Coloured pigments used :
GREEN
BLUE
RED

Firstly i mixed some red silicone up and using my finger rubbed it into the folds of the skin and in between each finger/thumb.

To give that kind of dead look i rubbed in some blue silicone at the center of each finger/thumb. I also did this on the nails. I recommend you use black for the nails, but i didn't have any on hand, HAHAHAHAHA! get it didn't have any on hand! (shut the hell up Phil :@)

If your still reading, then we can do the veins. I mixed up some blue/green silicone to get a veiny colour. Using a small paint brush i brushed small amounts of silicone over where the veins came through in the casting.

That's pretty much it, if you do come to try this then you will notice that you can't just slab a load of silicone on and expect it to look good, you must play around with it and look at your own hand for colour reference. If your looking for a dead look then use blues and darker colour's, if your looking for a healthy look then the flesh coloured pigment base as well as different shades of red silicone will give a great realistic effect.

Helpful Tips
Use black/blue on nails for a dead look
Use white on nails for a healthy look
Be creative
Wipe off some silicone, it shouldn't be dripping down the hand/prop unless your adding blood.
When you add wet silicone it will be very glossy, this should die down a little as it dries.



I also made a severed finger, i used a cut down PU bone with this. Firstly i cut a 4mm hole into the silicone, I inserted the bone and secured it with lots of red silicone. By mixing the red/blue silicone I achieved different shades of blood. Then i just let it drip down the sides of the finger.


ANOTHER TIP! If you place the painted hand/finger/prop under a bright and hot lamp then you will notice it dries in about 10-20 minutes!

Please ask any questions you want answering.

Thanks for looking
Phil

Hey Phil. Very interesting stuff here. The hand looks quite realistic! Very nicely done.
I'm not at all familiar with working in silicone yet, but it's so realistic I've got to give it a try sometime down the line. Good going! Thanks for sharing the info!

Thanks for those very kind words Chop Shop, they mean alot coming from you!
I highly recommend you try something with silicone, it's great fun to work with, although very sticky :P
Thanks Again
Phil

awsome job ....... i dont think it could look any more realistic then that ........all the detail and colors is just .....WOW!!!!!!!!!!