The RESIN CASTING POLL and advice topic

my dad's made some moldings for columns on our house with the process. he cut the models from a rubber block, cast them, remade the models, recast, then sanded them to the right shape ( )

Hi,
This was actually the second resin casting article (that I know of). In my case the
high initial cost is what is keeping me away, then the fact that I have to mailorder
is another factor. I heard or read something about using Westland scenics latex
molding rubber and JB weld 2 part epoxie for simple casts, anyone done this?
Good Hunting,
G.W.

I've been creating masters and resin castings for many years - and it's not hard at all to do successfully. You just have to have a little patience and perserverance.
You also need to think about the item you're casting - remember, without prohibitively expensive vacuum chambers to evacuate air bubbles from the RTV or the resin, or resin injection molding machines for casting, the simpler you make the mold, the higher the likelihood of success for the average modeller.
You'll find that the tiniest surface details on the master will be reproduced perfectly in the mold - even dusty fingerprints or marks in the mold release will be replicated, so take care to mold as perfect and clean a part as you can - the better the master, the better the copy. A crap master produces crap copies.
It's unlikely that the RTV latex rubbers and polyurethane casting resins that you'll want will be available in your LHS or general hobby store. I get mine from a place called One Stop Plastics here in Melbourne - they supply resins, fibreglass, kevlar and other monomers to industry - and they sell to the public. They've got everything and anything you might need. They're able to give advice on the best product to use for a specific application. When in doubt, seek out the experts. The stuff is expensive, so mistakes and blunders are rather costly. Avoid them if you can by asking questions.
Remember, softer RTV is better for complex, detail filled masters like high detail cockpits, prop blades, engines and the like, while the harder stuff is better for simpler structures like drop tanks, missiles and simple symmetrical pieces.
The softer RTV will degrade and tear quite easily when you start pouring resin - so you might not get very many shots out of a very soft mold - the harder RTV lasts longer and you can get more shots out of a single mold.
I've used several different RTV latex types - some by Wacker, some by Rhone-Poulenc, some by 3M or DuPont (can't remember which) - some hard and some soft - they're all good for their intended purpose - you can also make an RTV a little softer by adding up to 10% by volume silicone oil - just mix it in.
Polyurethane resin tends to dry out the RTV molds after a while - so a good silicone spray as a mold release/conditioner will help make them last a little longer.
Resins come in many formulations - from soft to hard, brittle to tough - I've even used a resin designed to fill the holes in bowling balls when the fingerholes are moved - the stuff was that tough. They also can differ quite significantly in their pot life (the time you can play with it before it turns to gel) - some have a pot life of 90 seconds and a demold time of 10 minutes, some have a pot life of 10 minutes and a demold time of 4 hours.
Pick the one that best suits your needs.
Resin is incredibly hydroscopic - it absorbs water and humidity from the atmosphere like a sponge - and excess water in resin causes frothing and results in resin parts that have a interior texture filled with tiny air holes - not good - so you have to use the stuff as quickly as you can - once opened, the shelf life is very limited. Never pour resin on a rainy or humid day - it's a waste of money.
A spray can of inert gas (called a dry air blanket) can extend the shelf life of resin - it excludes the water vapour filled oxygen from the resin container - just spray it into the resin bottle and quickly replace the lid.
Any quesrtions? Just email me on the link below and I'll help in any way I can.

Thanks for your outstanding response, LeeTree,.....much appreciated.
Hopefully as I get further along in my modeling career, I will be able to afford expanding into the resin casting area!

Man! I just read this poll and I'm surprised it's not filled with beaucoupe' responses and hints! I've done some casting and have had mixed results, mostly with the product choices not the reproductions altogether.

I've had good results with casting ammo cans, radios, bed rolls and bags of every type, and Jerry cans with embossed features and resessed lettering all with good results. I've even tried a few crude "masters" made from Fimo with good results.
I have had some problems with multiple surface moulds such as handles and MG's but I'll try other methods such as the two mould method. If that dosen't work I don't know what I'll try.
I've had good results with a product called 36 xxx from Vagabond and a product they sell for RTV called Circle K contact them via www.vagabondcorpoation.com

What I'd like to find is a resin with a low viscosity and slower gell time so I can try finer detailed stuff like jerry can handles and MG's and small items like canteens. The biggest two problems I've encountered are rapid gell (begining to set up before all the mix is used) and medium to high viscosity preventing a good flow into small areas in the mould. Air pockets have been a minor nusiance but occur mostly when I try one too many "pulls" in a short span. I find I have to clean and dry and "rest" my moulds after five to ten pulls, depending on the moulds and complexity of the copy/master.
feel free to contact me via e-mail (see my profile ) if you want to share info and tips off the forum.
I'm hoping to see some articles from Fine Scale (hint hint) for intermidiate and advanced casting techniques in future articles.
till then keep trying and look on line for resources, that's how I found Vagabond.