questions on resin casting

[Fortescue-Smythe]

To make some headway with my Space:1889 project (which went into hiatus just after conception), I'd like to cast some of the smaller Martian hull types in resin.
I plan to do Styrodur masters of the hulls in 1/300th, which makes them something between 2" and 4" in length. Just the basic hull shapes, adornments will be added to the individual ships after casting.
Now, I've seen this site http://www.tabletop-terrain.com/archives/2006/08/26/656/ on mold making, which looks just like what I had in mind. Which brings me to my questions:
(1) Could you use RTV molds such as these for casting in resin?
(2) What kind of vinyl is RTV, exactly, and where would you get it in Germany, or Europe?
(3) What sort of resin should I use for casting and, again: where could I get that?

Can anyone help me with that?
Claes

[Hammers]

Alumilite is not whagt I have been using but it is one of the larger hobby resin brands in the US. It is apparently available in the UK. They also sell mold material:

http://www.nigellawton009.com/PayPalCasting.html

I think I have seen a Dutch csupplier to but I have no address.

RTV rubber means Room Temperature Vulcanization rubber which is exactly why you should use it on styrene plastic masters since it doesn't generate a lot of heat when setting.

[Fortescue-Smythe]

Thanks for confirming the 'compatibility of materials', and...
...yikes, that's expensive.    I guess I'll google around a bit to see if there's a cheaper supplier somewhere. So the work on the masters can start, at any rate.

[Westfalia Chris]

You can get good-quality RTV silicone, of the Glorex Brand, at the "Idee Creativmarkt" hobby store chain. Other hobby stores, if well-stocked, might carry such stuff as well.

You must be prepared, though, to pay between 20 and 35 Euros for half a kilogram of the stuff; larger pots come slightly discounted, but you need a lot of the stuff, so it´s best to keep the masters small and devise the mold size economically, ie with maximum widths of RTV of about 5mm. If mixed correctly, this is perfectly suitable and durable.

[Fortescue-Smythe]

Thanks, Chris, I've found some sort of online supplier for 'Glorex' on german ebay.

[Hammers]

You must be prepared, though, to pay between 20 and 35 Euros for half a kilogram of the stuff; larger pots come slightly discounted, but you need a lot of the stuff, so it´s best to keep the masters small and devise the mold size economically, ie with maximum widths of RTV of about 5mm. If mixed correctly, this is perfectly suitable and durable.

Aye. No one said resin is cheap.

[Westfalia Chris]

I didn´t talk about the resin. That´s the RTV alone. Resin is even more expensive here in Germany.

[Hammers]

Sorry, Chris. That's what I meant.

Anyway it is a shame and I wonder why. Is it the limited pot life?

[ChukTuttle]

I don't know their policy about shipping overseas, but...

http://www.smoothonsecure.com/store/

[Westfalia Chris]

Anyway it is a shame and I wonder why. Is it the limited pot life?

Maybe that, but I strongly suspect that since it is a specialist article, compared to, say, coloured paper and furs for teddy bears, they charge a premium. However, my local store is well-stocked for casting needs, so if you´re prepared to pay the price, you get good stuff.

I mainly use syntheticeramics for casting, which are cheap (5 Euro per kilogram) and, for the price, acceptably durable. Resin is some 20 Euros for 250 grams.

[WitchfinderGeneral]

In Germany I ordered my resin and silicone from www.marronnier.de
I compared prices for some weeks and I found that Marronnier was the cheapest (let's say: the least expensive). They shiped fast, no problems at all and their productes were all very good.

I'd like to give you advice at 3 points:
1.) When you buy chemicals (resin, silicone,... what ever) that come in 2 components (filler and hardener), look that you get only those you have to mix 1:1 or 1:2. You won't want to mix everything (a whole liter or even more) at once. And when the stuff is 1:200 you'd have to mix a cup of filler with 1 drop of hardener, which is very difficult.
2.) You don't have to use pure resin. There are filling powders (silica or aluminium or something) you can mix in the resin. You can mix up to 3 parts filling powder to 1 part of resin. When you use the filling powder, the resin gets thicker, so it won't take details of the mould well any more. But when you only want to do big, rough parts it shouldn't be a problem.
3.) Think before you cast the mould. I often used too much silicone because there was too much "blank" space around the master, that I could have filled with modelling clay or wood before I poured the silicone over it. Also try to calculate how much silicone you'll need for the mould, before mixing the components together.

[Hammers]

...I mainly use syntheticeramics for casting, which are cheap and...durable. ...

Is that the same as dental plaster?

[Hammers]

In Germany I ordered my resin and silicone from www.marronnier.de

I will have to look at them up to.

I'd like to give you advice at 3 points:

I'd like to add two points:
4) For precision_always measure the ingredients by weight and to the gram on an electronic paper scale. The need for this may vary between products but since the material is fairly expensive and sensitive it is very annoying to make one of the following mistakes: too much hardener makes the result brittle, too much resin base and it will set sticky or won't harden at all.
5) Keep the mold rubber, resin base and hardeners in the freezer and their shelf lives will last much longer. Especially the rubber.

[Westfalia Chris]

...I mainly use syntheticeramics for casting, which are cheap and...durable. ...

Is that the same as dental plaster?

It could be. Basically, it is a water-soluble powder laced with synthetics that make for a much harder and denser surface than usual plaster. I don´t know, but dental plaster is reputed to be of similar hardness. I use "Stewalin" by Glorex of Switzerland almost exclusively.

[Fortescue-Smythe]

Thanks for all the input, everybody. That should get me well on the way. Right, so all I have to do is whip up some masters....
... he said, vanishing for two months.  :roll:
I'll post the masters eventually, if only to check that the shapes are castable.