Casting issues!

[Blissful Brushes]

+++

A disclaimer here - I'm not going to be using this to cast any FW/GW products, this would be for the bits that I create myself.

+++

 

My issue is that I've been sculpting in a modelling clay called plastiline (http://plastiline.fr from here) and it never cures and doesn't bake - 30 degrees + and it starts to melt - which means that I need to create a mould for the stuff I'm sculpting and cast the models/bits to actually paint them.

 

Because the clay will never cure on its own and is relatively delicate, I think I need to be able to create a mould with a silicone/rubber (or something) that is liquid, and then work out how to pour liquid resin into the newfound mould.

 

If anyone knows of any products that meet this description I will be eternally grateful!

[Bung]

There is something called mould silicone and epoxy resin for miniatures.

There are some modelling shops for this stuff in germany . You just need to look a bit if you find something in your area.

[Subtle Discord]

How serious are you?

 

There's a world of products out there that can do exactly what you want, but it comes down to how much you want to put in (labour, materials, and money), how much learning you're willing to do (and how much trial-and-error you want to undertake), what kind of results you want to produce, and how many copies you want to make. Elaborate a little on just what you want to replicate, how much you're willing to invest, and what results you're striving for.

[Blissful Brushes]

There is something called mould silicone and epoxy resin for miniatures.

There are some modelling shops for this stuff in germany . You just need to look a bit if you find something in your area.

 

Thanks for that - I'll give it a look now. A material name is something I can work with to narrow down what I need!

 

How serious are you?

 

There's a world of products out there that can do exactly what you want, but it comes down to how much you want to put in (labour, materials, and money), how much learning you're willing to do (and how much trial-and-error you want to undertake), what kind of results you want to produce, and how many copies you want to make. Elaborate a little on just what you want to replicate, how much you're willing to invest, and what results you're striving for.

 

Thanks for the quick responses.

 

Below are the things that I want to be able to reproduce at the moment, though I do have a Primarch sized sculpt of the Emperor in progress and the beginnings of Thunder Warriors that I do want to be able to cast.

 

The issue with the material that I'm using at the moment is that as it doesn't cure and is relatively sensitive to pressure I need to create a mould quite 'gently' to not ruin details.

As far as the plastiline that I'm currently using this is what was recommended to me by Simon Egan of FW fame, of course we both didn't take the fact that he's got a professional casting team behind the glories that he produces.

 

They're roughly scaled to Terminator/truescale marine size

Torso

 

Shoulder pad

 

Helmet

 

Before I spend hours finishing these I need to work out this casting/mold creation lark

[Bung]

Personly i would have gone with an oven hardening putty like Super Sculpy or Bees Putty for sculpting. That way it would be easier to have a duarable prototype to remake the moulds if necessary.

[Kinstryfe]

Yes, there's a product I've used in the US called Alumilite (brand name). They make a liquid 2 part silicon mold material that dries hard, and a 2 part liquid resin that does the same. This kind of thing is likely the best for that job.

 

HOWEVER

 

It can be fiddly, like any casting material, and there is almost a 100% chance that your sculpt would be destroyed by the mold making process. Sadly I can't think of a single molding technique that wouldn't do the same. If you're going to be serious about casting, you may really want to expand into other materials. Something that never cures and can melt isn't going to play well with most molding agents.

[Arkhanist]

I think for plastiline you need a room temperature (RTV) silicone to make the master mold. The curing agent will determine stiffness and setting time, but I believe it's more likely to work with a liquid version into a casting box, and a slowish time to vulcanise at room temperature (up to several hours) You'll want to use a usual two part mold process using some modelling clay - example of that process here:

 

https://youtu.be/FQ1A7ZjTsx8

 

You'll probably need to buffer the model from the temporary modelling clay (so it doesn't stick together) with some release agent - the modelling clay only needs a solid join at the silicone/clay line, the rest of the master can be in a void; I've also seen clingfilm used to protect a delicate master from the temporary clay, and putting it in the fridge will harden the plastiline somewhat before casting.

 

Given it's cast at room temperature and a fairly soft silicone, it shouldn't destroy the plastiline master. I believe RTV silicone is more expensive than cheaper tin based silicone though, and not as robust for bulk casting.

 

Once you have the RTV silicone mold, you can then cast directly with two part resin for smaller runs. Or you can create a resin master from the RTV silicone mold and create a more robust high temp tin silicone mold from that for higher quantity runs and/or metal casting.

 

For the RTV silicone, I've heard of the mold star range - I'm sure there are others.

[Subtle Discord]

Sorry for the quick reply and then leaving you hanging. I've been juggling quite a few things the last little while.

 

Taken from another thread about casting that I responded to and edited to add more information:

 

For under $50 you can get all the materials you'll need to do press moulds for simpler replications; for roughly $100 you can get all the materials to do simple RTV rubber moulds and use 2-part urethane resin to create higher quality replications, and for roughly $250+ you can create a Pressure Chamber to push the quality even higher; beyond that price point you're looking at investing in a Vacuum Chamber which pushes the process even further. The largest return on the investment will be seen in the quality of the parts created and how much work will be required after casting to deal with defects like bubbles; basically, more money and labour equals cleaner casts that need less cleanup.

 

$50 = Press moulds or very simple RTV (Room Temperature Vulcanizing) rubber. These can produce surprisingly good replications but require lots of practice and effort to get the best resutls. Even at it's best you'll likely lose detail and sharpness.

 

$100+ = Here you can invest in good RTV rubber and get some two-part Urethane resin to produce parts that are tough and strong. Your largest obstcal at this point will be bubbles and much technique will be needed to avoid and eliminate them. If the casts are for personal use you can usually deal with bubbles and clean them up as you see fit. You'll know how much work you're willing to do.

 

$250+ = At this point you can get a Pressure Chamber up-and-running and will help deal with bubbles in a large way. You'll need a Vacuum Chamber to really reach near bubble-free casts without too much manual effort, but the results are really amazing at this point, with parts that reproduce everything down to the tiniest details (including flaws).

 

One key thing to remember is that casting materials do have a shelf life; RTV rubber compounds will thicken and the 'A' compound of casting polyurethane will turn to 'slush' as it slowly reacts to the moisture in the atmosphere. If you want to go this route just be aware that you don't want these materials sitting around for longer than 12 months or so. There are ways to extend the life of some products but it's best to aim to use them in a timely manner and buy quantities that make sense to a given situation.

 

Have a look at my Legion Rising WIP p'log to find my personal insights into the resin casting process. The content is a bit scattered within the thread but it documents my experience with casting from my very first mould all the way to what I'm up to today. I've been using SmoothOn products since the beginning and they're very good. They have a wide range of products for different purposes and lots of videos and tutorials to really let you understand how to use the products and what results to expect. Even if you can't get the SmoothOn brand in your area have a look at some of their videos to get a better idea what you'll be doing; additionally, have a look at any online source you can about resin casting, it doesn't matter what the subject/object of the tutorial is for, you want to see process and technique that you can adapt for your purposes.

 

SmoothOn's MoldStar 30 (50/50 mix ratio) is a very good RTV rubber to start with that mixes with low viscosity so with careful pouring you can make very good bubble free moulds; the moulds it makes will be a bit softer than other rubbers (trade-off for the low viscosity) so they won't make as many replications before they start to tear and wear out, but still plenty for most hobbyists. MoldMax 30 would be a good starting point if you have a Pressure and/or Vacuum chamber, but it's a 90/10 mix ratio so you also need accurate scales for proper mixing. For casting resin you can try SmoothCast 300, but it sets up very quickly so you must work fast; 3-minute pot life (mix and pour time) and 15-20 minute cure time means you can have parts in half-an-hour. SmoothCast 305 will be much more forgiving, with a 7-minute pot life, but it will take ~40 minutes to cure; the advantage here is that you can mix and pour slowly to avoid bubbles in your casts and you have more time to bump, tilt, and pinch the mould in an effort to knock stubborn bubbles free.

 

You are right that if you're using a sculpting 'clay' that is never fired so it won't ever be completely hardened, that it can potentially be an issue. You can still cast it, but as it's been mentioned, there are very good odds that you'll damage the original; once you get used to making moulds this might not even be a problem because if you can make the mould correctly you'll be able to get at least one nice clean cast out of it and that can be used as a future master. If the part is properly treated (or the right material) it will actually pull free of the moulds very easily once the rubber cures so there is hope that most things will survive the process, but any delicate details will be much more prone to damage and results are very contingent. I would suggest sealing the sculpts with something that can soak into the clay and dry/cure into a protective skin; spray with a good primer, paint on a layer of acrylic varnish, or some other treatment of some sort. All you need to do is create a barrier to prevent the RTV rubber from soaking into the part binding with the surface of the object; people use a special oil treatment to cast organic things like wood, masonite, rocks, and bark, so it is very possible to pull off.

 

Make sure your masters are as flawless as you can manage. Any details no matter how small they are (even fingerprints) will be replicated by the casting process. Once cast they're as easy to work with as any resin model, so cleanup is always an option, but try to avoid any issues before you make them permanent. Be ready to do quite a bit of reading and to watch several videos more than once; it will take a few tries to get the hang of it, but once you know what you're doing it's not hard, it just takes the time it takes to make the mould. Start with some small simple bits to get the hang of it and then try something more challenging.

 

Hope this helps, feel free to ask questions or for more clarification. mould making is a bit intimidating, but if you're willing to figure it out you'll have an amazingly powerful skill at your disposal in the future for all sorts of applications. Heck, in the right industry it even looks good on a resume, despite being a hobby related process in this case. :)