Resin properties???

[Arannz]

For those who haven't seen it I'm sculpting the King of the Dead (from the Lord of the Rings Return of the King movie) as a bust:

http://img208.imageshack.us/img208/2332/kotd14a3ru.jpg

I have found a place that can make the rubber molds for me, but I need to do the resin casting myself. I've been looking all over the place at different resins, but I'm still pretty unsure about what things like shore hardness, tensile strength and viscosity mean in practical terms.

It would be great if those of you who have casting experience could relate to us newbies what your recommended qualities are in a resin for casting a detailed bust or statue such as the King of the Dead (above)! :D

i.e.

Shore hardness (D) - presumably this determines how hard the plastic is if you were to try pressing an object into it or scoring/carving the surface, but how much is too soft and how much is too hard? Does a harder resin mean it is more brittle and fine parts are therefore likely to snap?

Tensile strength (PSI) - how is this different to shore hardness? Does it determine the flexibility of the resin, i.e. a higher tensile strength means a more flexible/less brittle casting?

Viscosity - a lower viscosity can help reduce air bubbles by making it easier for them to rise to the surface of the poured resin, but how low does it need to be, especially if you don't use pressure or vacuum casting?

If anyone can post their favourite values (or value ranges) for things like shore hardness, tensile strength, and viscosity it would be much appreciated! Alternatively post your favourite resins by name, so others can look them up.

Thanks heaps!

Aran

[Sniper]

hot!!!!!!!!!

[RickDTM]

Arannz - Post this over at the Sculptor's Forum in the Clubhouse as well. There are a TON of folks over there VERY familiar w/ the various properties of resin.

[Arannz]

I posted it there first Rick! Thanks for the reminder though.

So far I'm leaning towards a product called smooth-on. There is even a distributor in Auckland, just down the road from where I live! :buttrock:

I don't know if they deal with the public yet or what the prices are like....

[enemyilaf]

Smooth-on makes a really good resin. I have used the smooth-cast 300. It makes a very solid part. Something you can drop on the floor and not worry about denting or breaking. That is shore 70.

Tensile strength is how much you have to pull on the plastic for it to break. Not sure it makes much difference in your casting though.

The SmoothCast 300 is water thin, but can you still get bubbles... Yes. I assume others have different ideas on how to get rid of the bubbles. But with no vacuum machine, there are a couple of things you can do.
1) is to fill the mold about 1/3 to 1/2 full and slowly rotate the material around the inside of the mold.
2) is to make sure the mold has plenty of air vents to prevent air bubbles.
3) is to fill the mold and then tilt and tap on the mold. Basically jar the air bubbles out.

I am not sure I would use SmoothCast 300, since it has a 3 minute pot life... SmoothCast 305 has a 7 minute pot life. Basically consider this as the amount of mixing time and time for beating out air bubbles.

All the molds I make are fairly small, so a 3 minute pot life is more than fine. I can not tell how large you sculpt is, but it looks rather large.

By the way this is a very nice piece you have made.

ilaf