What resin do you use to cast and casting questions

[Hidden Jitsu]

So the time has come and my first custom sculpt is almost ready.
So i'm getting prepared to cast these up.

I know how to make moulds and what not but it is the resin that
i need more info on.

I was thinking Polyurethene casting resin , but what is polyurethene
liquid plastic?
Also what are fillers for and how are they used.
Do i need to spray the inside of the mould with mould release stuff?

Is it possible you get good results without using a de-gas chamber?

Info would be great as i can't afford to waste materials and want my customers to get the best quality cast.

 

[Alastair]

Hi Hidden Jitsu,

Mouldlife in the UK carries a whole range of casting supplies, I use their silicones here in Australia. Here is a link to thier polyurethane page. https://www.mouldlife.net/polyurethane-fast-casting-sytems-31-c.asp

 

[robbiethepainter]

Here in the US a lot if us use material from the company Smooth-On. They have a really extensive website with how toos.

WWW.smooth-on.com

 

[Fangs of Death]

Polyurethane resin is as you say, just liquid plastic. Tougher than polyester, no breakage, better shrinkage properties. Mould release using RTV silicone moulds not required. I don't use degas, just have to be careful, and try to get most of the bubbles out beforehand by rolling it gently around the potsides a few times. Can also use the "bombing" pouring method--pour in a thin stream from altitude, makes the bubbles burst before the stuff hits the mould.

Filler is for reducing shrinkage, heat and saving resin. Special fillers for various finish effects (metal powders, etc)

I use resin and fillers from CFS (UK). Cheaper than eBay, even.

 

[Hidden Jitsu]

Polyurethane resin is as you say, just liquid plastic. Tougher than polyester, no breakage, better shrinkage properties. Mould release using RTV silicone moulds not required. I don't use degas, just have to be careful, and try to get most of the bubbles out beforehand by rolling it gently around the potsides a few times. Can also use the "bombing" pouring method--pour in a thin stream from altitude, makes the bubbles burst before the stuff hits the mould.

Filler is for reducing shrinkage, heat and saving resin. Special fillers for various finish effects (metal powders, etc)

I use resin and fillers from CFS (UK). Cheaper than eBay, even.

Ok that sounds like all great advice and thanks.
Yeah i got some medium RTV silicone.
Also doe the powder not make the resin thicker and less pourable?
Well i don't have a clue how the resin works as it is in 1kg lot's 500g of resin and 500g or hardener.
I don't know how much resin 1 head would use , but i guess if i pour water into the mould and then into a cup it would give me a rough idea.
Also when making the mould do i need to paint the face with the RTV first or just pour it on?

 

[Hidden Jitsu]

This seems like a good site and they are pretty cheap too

 

[Fangs of Death]

If you stick to no more than 50% filler, the resin pours almost normally.
You may not have room to paint the silicone on the head, I know I haven't--I just run it in the side, thin stream to about a third mould full, then lean the mould this way and that to get the stuff under the undercuts, using a piece of wire to get the bubbles out of the ears, nostrils etc. Then top up, maybe doing it again before the top.

With RTV you have plenty of time to do a careful pour. More care, less chance of an inconvenient bubble in your mould.

Heads take about 20ml of mixed resin. I've made a little plastic stick for poking the hair and features, to get the little air bubbles out. The stick has a curved end for poking ears and nostrils. Ears trap bubbles! And eyesockets. Have fun!

 

[Hidden Jitsu]

If you stick to no more than 50% filler, the resin pours almost normally.
You may not have room to paint the silicone on the head, I know I haven't--I just run it in the side, thin stream to about a third mould full, then lean the mould this way and that to get the stuff under the undercuts, using a piece of wire to get the bubbles out of the ears, nostrils etc. Then top up, maybe doing it again before the top.

With RTV you have plenty of time to do a careful pour. More care, less chance of an inconvenient bubble in your mould.

Heads take about 20ml of mixed resin. I've made a little plastic stick for poking the hair and features, to get the little air bubbles out. The stick has a curved end for poking ears and nostrils. Ears trap bubbles! And eyesockets. Have fun!

Splendid thanks for the info buddy , also regarding the RTV latex
how much of the blue stuff i think it is called catalyst in the RTV?
As i have no scales to weigh the stuff.
Is there a certain amount per ml i need to use?

 

[Fangs of Death]

Should have a leaflet with it. If it's an indusrty standard, I'd say it's the same ratio as mine, it'll be 10:1.
Whichever, the catalyst supplied will be enough to do the entire tub of RTV, so just split your components equally for small batches.

 

[Hidden Jitsu]

Should have a leaflet with it. If it's an indusrty standard, I'd say it's the same ratio as mine, it'll be 10:1.
Whichever, the catalyst supplied will be enough to do the entire tub of RTV, so just split your components equally for small batches.

Yeah i got a leaflet but it just waffles about weighing the silicone.
But yeah the catalyst does the full 1kg silicone and then half does obviously half of the silicone.
I guess not enough will stop it from curing?

 

[Fangs of Death]

Just slows it down, unless you get it horribly wrong. If your proportions look right by eye, you're good to go. I mark my catalyst bottle with graduations--that's easily accurate enough.

 

[sinag55]

Hi, guys. I'm going to start recasting a head that I sculpted. Someone told me that I should buy RTV 585 for more detail. When I looked at the website of a local store. It says that Use "RTV 585 for originals with little undercuts and RTV 524 for more complicated molding."

Thanks in advance for any advice on this.

 

[Hidden Jitsu]

Heads take about 20ml of mixed resin. I've made a little plastic stick for poking the hair and features, to get the little air bubbles out. The stick has a curved end for poking ears and nostrils. Ears trap bubbles! And eyesockets. Have fun!

So resin wise it says do it by weight but is it not usually
exactly half of each but as 1 is thicker than the other would one be heavier?

 

[Fangs of Death]

Can't help with that, my resins' parts are both the same viscosity.
Made a mistake with the 20ml, it's more like 30ml for a necked head, I think.

 

[Hidden Jitsu]

Can't help with that, my resins' parts are both the same viscosity.
Made a mistake with the 20ml, it's more like 30ml for a necked head, I think.

I borrowed some scales and done as it said but to be honest it was equal amounts of resin i had to use.

Right my first custom head arrived today nothing special just a generic sort of robot waste lands head for a custom i'm doing.

BUT! It is neckless , have you any advice on moulding it so i get the inside of the head.
Or will i have to fill the hole and then dremel the resin out which i really don't want to do as i hate resin dust.

 

[Fangs of Death]

I've never done a neckless cast. What I would do (I expect) would be to use a core of some kind, that just pulls out after curing, leaving you with a hole to shape. Would need to be slightly tapered...a straight plastic one (in my experience) will come out--if it isn't stuck--but needs some force. I used a thin screwdriver as a tommy bar.

Might be worth making a "neckless casting" thread to draw in some assistance--could be there's a popular way of doing it.