Resin Which Type Is Best

[big F]

Firstly I hope this is in the right section. Well the time has come for me to start making a few casts of model parts in need duplicates of. In the distant past I worked for a company that made stuff like jewllery when we wanted a duplicates for making casting molds we used RTV silicone for making the low temp molds for our destroyable duplicates. when it can to the actual resin we used one particular brand, I can t remember what, i suspect that this was what our suppliers had. No I never paid attention to the type brand and cost as at the time these were unimportant to me, If I ran out I just went to the stock room and got more etc.

Now I want to do stuff for myself I need help on deciding which type of resin to get. I already have some RTV for the molds. which type of resin works well for making resin model parts ?

on eBay I found this resin

Is it any good also what sort of release agent works best, again this was a subject I never cared to remember at the time.

On a side note after I have made my molds Is there someting I can use to test them rather than waste resin, (in the old days this also was not a problem) I was thinking of using wax or something like plaster of paris.

Any info from someone who has tried it would be most appreciated.

Edited December 20, 2005 by big F

[fernarias]

The stuff you found on ebay is the same stuff that they use for Thai cast kits (worst stuff in the world). It's brittle and doesn't give you any detail. What you need is called polyurethane resin. Here some good stuff at a cheap price:

http://www.smooth-on.com/plastics.asp#320

Oh, and forget about RTV Silicon for molds, that's old school. The new thing is Urethane Rubbers. They offer the same amount of detail and shore hardness as RTV Silicon but will last longer than 30 molds. They are also here:

http://www.smooth-on.com/urethanes.asp

F.

[big F]

The stuff you found on ebay is the same stuff that they use for Thai cast kits (worst stuff in the world).  It's brittle and doesn't give you any detail.  What you need is called polyurethane resin.  Here some good stuff at a cheap price:

http://www.smooth-on.com/plastics.asp#320

Oh, and forget about RTV Silicon for molds, that's old school.  The new thing is Urethane Rubbers.  They offer the same amount of detail and shore hardness as RTV Silicon but will last longer than 30 molds.  They are also here:

http://www.smooth-on.com/urethanes.asp

F.

354409[/snapback]

Thanks for the info. I think I have found a company in the U.K that supplies the "proper" Urethane based resin. When Ive run out my current large tin of RTV I will look at the newer urethane based alt.

Edited December 22, 2005 by big F

[MechTech]

Thanks Fernarius, I hadn't thought of using urethane rubber for some reason. I'm going with that my next run. No degassing! Awesome! Even turning my molds so the bubbles won't show up doesn't always help. Now if they could just get the bubbles out of the resin without degassing.

Big F, if you find a good place in England, please shoot me a PM. Having to order from across the pond is, well, ponderous! That type of resin you mentioned first was what I first used. It stinks to high heaven and so do the parts. My wife loved that! Another good source where I normally get my stuff is Micromark.com. They have ALL the accessories you need and they even have metal molding supplies! I am a big fan of tinting my resin. It saves paint and adds a proffesional touch to production runs. Just a little drop and you have your part molded in color! - MT

[kanata67]

smooth-on without a doubt. The stuff that can be made with their products. The resin plinth on a plinth at trafagar square for instance . They have a starter pack you can buy once at a discounted price. I have one but haven't gotten around to any of the numerois projects I want to tackle yet. Heck, been in this house over a year and my stereo still isn't hooked up .

anyhow... nimba creations in england uses smooth-on so perhaps they might sell it as well? www.nimbacreations.com nimbacreations@hotmail.com tel [44] 01271 343264

maybe that will help?

[big F]

kanata

You are a mine of information as usual, gonna check them out.

Mechtech I am waiting for a reply from a posible supplier who`s based in Cornwall, so when I do I will let you know, they supply many many different types of resins and RTV etc

[Ryuji]

Another option:

http://www.axson.com/

Axson UK

15 Studlands Park Ind. Est

Newmarket CB8 7 AU Suffolk

UK

Tel: (**44) 01638 660062

Fax:(**44) 01638 665078

e-mail: sales@axson.co.uk

I used smooth-on resin,but I didn't like - sometimes happened a strange reaction with silicon rubber...

I tested Axson resin and I liked the result - I will cast Komillia with this.

Edited December 24, 2005 by Ryuji

[big F]

Another option: 

  http://www.axson.com/

  Axson UK

  15 Studlands Park Ind. Est

  Newmarket CB8 7 AU Suffolk

  UK

  Tel: (**44) 01638 660062

  Fax:(**44) 01638 665078

  e-mail: sales@axson.co.uk

  I used smooth-on resin,but I didn't like - sometimes happened a strange reaction with silicon rubber...

  I tested Axson resin and I liked the result - I will cast Komillia with this. 

354759[/snapback]

Just looked at the site. Which resin are you using as there a quite a few, some of them need vacuform to work. most of the work i want to do is eaither two piece casting or open casting.

[Ryuji]

I tested Fast cast F-18 (pot life - 3'30")

http://www.axson.com/Axson/fiches/anglais/f18-gb.pdf

There is F-16 (pot life 2'30") , F-19 (7') , F-31 (1'50"), F-33 (2') and F-50 (40')

[captain america]

For what it's worth, I advise extreme caution using urethane rubbers to make molds with. The stuff is easy to use and cheap, but if your master isn't PERFECTLY sealed with mold-release, the rubber will stick to it. With silicone molds, you get better detail capture and no release agent is necessary.

Then there are the castings. Without an effective release agent, your casting will essentially fuse itself to the mold, so you *MUST* apply a release agent every time, and on *every* nook & cranny of the mold. What's more, urethane-to-urethane release agents (or at least none that I've ever seen) weren't designed with post-cast painting in mind. So while you may end up with good looking castings, you may also find that no paint will stick to them no matter how much you scrub or clean them. This is why, to my knowledge, all the big GK manufacturers use silicone molds.

[big F]

Well I did a test cast using my RTV using some plastic pipe for mold wall and the cast up side dowm method using some molding clay as a negative for the pouring funnel.

It cast up o.k apart for a few voids which didnt go off. I can asume that these voids are due to fixing problems with the activator it was very hard to get it to stay mixed.

The docs with the silicone said it had a pot life of 30 mins and a curing time of 3-4 hours at 60-70 F . Well that was bull as it started to go off in the pot while I was still mixing in the activator. I was working in my outside workshop in about 6 c so I thought I should have had longer. Well anyway this method my not have been the best but as I only needed one cast from this mold so if it fails after that then no worries. Yesterday afternoon was spent kneeding moldling clay and rolling it all into a paving slab sized block. I have now made new molds which are shuttered in and sealed. I am going to cast the first sides tomorrow and then using the same shuttering the other sides as soon as it is ready.

I think the two part molds are the best as they allow you to fully cover the casting area with release agent whereas the tube type, where the mold is not fully cut in half it is always the risk you have missed a bit.

It certainly is a lot more costly when you have to pay for your own casting supplies and get more inventive casting non regular shapes. I love the smell of latex gloves and disposable plastic cups NOT!

[captain america]

Hi Big F.

The science of molding/casting isn't quite as difficult as some might believe, but it does, however, require a lot of preparation and precision when mixing components.

The air bubbles you speak of are created upon mixing of the silicone/catalyst; happens even with a mechanical mixer. This issue is rectified by de-gassing the silicone in an appropriate vacuum chamber. This takes about 15 minutes. I do this, and my molds are pretty much flawless.

Short pot life: generally, the specs in the product data sheet are pretty good. However, this depends primarily on the amount of material mixed, as well as the exactitude of the catalyst added; too much can cause the material to cure too quicky, etc. The best thing would be to check the PDS and if possible, cross-reference that info with a technician from the manufacturer.

[MechTech]

Thanks guys for the tips, and I might hold off on Urethane solely for simplicity sakes. All the stuff I'm using is 1-1 so it's a piece of cake. I am seriously considering getting a pressure chamber. I even purchased an air compressor to de-gas my resin in a chamber someday. New drill press comes first!

Resin set-up times vary like the tides! I've had the same resin set at varying times! It's all in the temperature, age of resin (older sets up fast for my stuff) even mold temperature. I heard of a guy puting resin in a fridge to slow the cure time. It worked, the resin never fully "cooked inside." Screwed up my mold with uncured goo too! Even after a couple of days, no catalyst affect.

I need to get a face mask respirator too. I've been modeling way too long long now and would like to keep my hobby and health!

[big F]

Thanks for the info Captian. Well i ws thinking that the catalyst may be the key to it all.

I was mixing in 100g ammounts ( I didnt want to make too much in one go ) and the instructions said that it should be mixed at 2 - 4% well according to the info sheet that was 80 drops of catalyst. That ammount turned it into a lake. So I figured that next time I would use less say 60 drops. If it dosent start to go stringy in a few mins then hopefully I will be o.k.

The manufactures web site is partially down at the moment so I cant get to talk to them.

Looking at the whole release agent area what is best. I have heard it all from Dont bother to use cooking oil from a spray can to go out and get silicone relese spray.

As there are several Professional casters here at M.W I think I would trust you guys more as firstly you do it for a living and secondly you have had experience casting the sort of stuff Im gonna cast, not like all the other info I have got from people casting model trains and Dungeons and Dragons figures

[MechTech]

As far as release agents go, I haven't messed with any "home remedies," but I usually use Vaseline for the two part silicone molds. Can't beat the cost. I actually did break down and buy the proper stuff, guess what, no difference. All of the resin I use is self releasing so I have no problems with mold release agents. For heavy undercuts and fine detail, the mold release agent is great to adding life to the mold in my case.