Newbie q: simplified casting process?

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PrimoOptimoso

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OK, this is going to sound stupid, but since all my costuming thus far has just been literally scratch building the worn pieces, it's totally different to me.

Let's say I wanted to make an armored chestplate - I dunno, use Halo or something in your mind as the example. So I have either me, or a duct tape dummy or lifecast of me, to work on. I build up the chestplate using all manner of foams, clays, cardboard, whatever and get that looking the way I want it.

Normally, in my world I would then paint it and wear it that way. But if I wanted it to be sturdier, maybe lighter weight, etc, I get the distinct feeling here that I'd want to mold and cast it. This is where I need just a rough explanation. I've seen the detailed tutes before, but I get distracted by all the detail.

Can you guys tell me in stupid-simple terms what the process is? I gather the following:
- build the above as a positive model
- jam that into a liquid (like silicone or plaster I suppose) and let that set, for a negative
- pour the final medium into the negative to make the finished positive.

Yes?

If that is correct, how would the finished positive get the back-end contours of my body? Can the dummy be pushed into the final medium that the positive is made of, while that sets?

Side question: What about pieces that you don't want to be solid between your skin and the outer surface (so you have airspace in between)? Different methodology altogether?

Sorry if this sounds stupid - it's just different than what I've done before and I'd love to make more sturdy and wearable pieces.

Thanks much
 

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I suggest reading up on learning how to lay fiberglass. You can do pretty much anything you want at that point. With regards to airspace between you and the armor - think about the inside of a football helmet...foam attached to the inside of the armor to act as spacers and allow air to flow through.

If you do use fiberglass, be sure to seal and finish the interior as well. Raw fiberglass on the skin isn't fun....and don't ask me how I know this... :)

J
 

PrimoOptimoso

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RPF PREMIUM MEMBER
I suggest reading up on learning how to lay fiberglass. You can do pretty much anything you want at that point. With regards to airspace between you and the armor - think about the inside of a football helmet...foam attached to the inside of the armor to act as spacers and allow air to flow through.

If you do use fiberglass, be sure to seal and finish the interior as well. Raw fiberglass on the skin isn't fun....and don't ask me how I know this... :)

J

Thanks, Jeff - actually with regard to the airspace thing, I was referring to the fact that casting something between a negative mold and a body cast would fill the entire space (you on the inside and solid material all the way to the outside surface), and am wondering how to cast something you want to only be a shell of the outer surface, hollow behind.

As for fiberglass - I'll look into it, but I highly doubt I have the facilities for such. I already have to do everything at the dining room table as it is now; the table on my deck is too fragile and small, as is pretty much the rest of the townhouse... Not to mention I have to do everything on the cheap.
 
Ah, gotcha....

Fiberglass can be done on the cheap - at least compared to casting resin and making rubber molds, but you'll still have to fabricate a set of masters.

J
 

Wesman

Member
I can see two ways. The aforementioned fiberglass is something you can do without any specialty tools, really. I do a lot of it. If I had access to a vacuumformer, I would always prefer that, and have made many armor pieces using ABS. Both still require sculpting a master pattern, the two processes are similar in that respect, but would be done slightly differently. Vacuumformed is cleaner, but fiberglass gives you a lot more flexibility in the process.
 

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PrimoOptimoso

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But again this is far more detail than the simplified process I was asking about. I just need to know all the parts of the process - to deal with materials and the minutiae once I have a handle on the process itself.
 
There really is no simplified process. If there were, everyone would be doing it and fiberglass and vacuforming and resin casting would be obsolete.

I've done fiberglass in my garage, before I had a shop. If you've got a drop cloth and a VERY understanding spouse, you could do it in your living room if you had to.

Your other option is build a vacuum-forming machine and with heavy styrene or ABS sheet. But...you only get one try per part...

J
 

PrimoOptimoso

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RPF PREMIUM MEMBER
There really is no simplified process. If there were, everyone would be doing it and fiberglass and vacuforming and resin casting would be obsolete.

I've done fiberglass in my garage, before I had a shop. If you've got a drop cloth and a VERY understanding spouse, you could do it in your living room if you had to.

Your other option is build a vacuum-forming machine and with heavy styrene or ABS sheet. But...you only get one try per part...

J

Guess I didn't mean a simplified process itself, but a simiplified explanation of the molding and casting process, as I'd tried to guess at enumerating in my post.

I do have an understanding soon-to-be spouse, but I also have a pair of big dogs and a daughter, so no space is undisturbed for long. :unsure
 

robn1

Master Member
Guess I didn't mean a simplified process itself, but a simiplified explanation of the molding and casting process...

Well in it's simplest form, for fiberglass it would be like this:

1. Make your master part.
2. Make a mold of the part. For fiberglass, the negative outer mold is all you need.
3. Lay up fiberglass in the mold. Done.

Now the details are what materials and methods to use, but that should simplify the overall process for you. Fiberglass is probably the fastest and cheapest way to go, and will have excellent results. But it's also messy.

Steve Neill is using fiberglass for his Enterprise built, look at his thread for details on the molding and casting. Of course you don't need silicone for the molds, armor can be done cheaply with plaster molds. But it's a good step by step on the general process.
 

PrimoOptimoso

Well-Known Member
RPF PREMIUM MEMBER
Ok, good deal for 'glass... Does fiberglass work for intricate detail like siicone apparently does?

And then the reverse of one of my above questions: since fiberglass lays up as a shell, what do you do if you *do* want a piece to be a solid thickness of material between your body and the mold? (like for instance 'armor' plates that conform to a lycra suit but have shaped thicknesses and ridges and such).

What I am trying to do is learn some new techniques, and have an idea beforehand of which methods will be more successful for any given costume, so I dont waste time and money as much as i tend to with unsuccessful attempts.
 

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Nwerke

Master Member
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It depends on what your final piece is cast in. If you're making rubber final items, then yes, as long as there aren't any major undercuts. If you want rigid final pieces with detail then no, don't make your mould of fibreglass.

If you want your final piece to be a two-sided item you will need to make two moulds, one for each half, and cast the front and back separately. You would then join them together and clean up the seams with putty and sanding.

Or, you could make a single mould (probably two-part, however) and cast the pieces in either foam latex or expanding urethane foam, or, rotocast them with urethane resin.
 

PrimoOptimoso

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It depends on what your final piece is cast in. If you're making rubber final items, then yes, as long as there aren't any major undercuts. If you want rigid final pieces with detail then no, don't make your mould of fibreglass.

If you want your final piece to be a two-sided item you will need to make two moulds, one for each half, and cast the front and back separately. You would then join them together and clean up the seams with putty and sanding.

Or, you could make a single mould (probably two-part, however) and cast the pieces in either foam latex or expanding urethane foam, or, rotocast them with urethane resin.

Heh - now you might see why I have been so confused with the details all these years: Your statement above was regarding making the mold itself out of fiberglass, while the post from robn1 was talking about making the finished item out of fiberglass laid into a mold.

It sounds like thus far it would be prudent to make smooth hard things like armor out of fiberglass and softer things like skin or muscles out of foam latex, which makes sense, but I guess I still wonder what to make intricately-detailed hard things out of.
 

PrimoOptimoso

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RPF PREMIUM MEMBER
Wait - Here's an even more basic line of questioning:

1. If I only plan to make 1 of whatever it is, is it even worth it to make a mold and cast something?

2. Then again, it sounds like for some pieces, that would really be the only way to make something light and strong enough to be wearable. No?
 

Gus76

Well-Known Member
RPF PREMIUM MEMBER
I believe you need two-part mold casting. It can't be called simple but it is definitely what you are looking for.

Ok, good deal for 'glass... Does fiberglass work for intricate detail like siicone apparently does?

And then the reverse of one of my above questions: since fiberglass lays up as a shell, what do you do if you *do* want a piece to be a solid thickness of material between your body and the mold? (like for instance 'armor' plates that conform to a lycra suit but have shaped thicknesses and ridges and such).

What I am trying to do is learn some new techniques, and have an idea beforehand of which methods will be more successful for any given costume, so I dont waste time and money as much as i tend to with unsuccessful attempts.
 

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Nwerke

Master Member
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Heh - now you might see why I have been so confused with the details all these years: Your statement above was regarding making the mold itself out of fiberglass, while the post from robn1 was talking about making the finished item out of fiberglass laid into a mold.

It can go either way. Some friends and I have been pulling fibreglass pieces from fibreglass moulds every weekend for the past several months. Doable if low-detail/no undercuts.

It sounds like thus far it would be prudent to make smooth hard things like armor out of fiberglass and softer things like skin or muscles out of foam latex, which makes sense, but I guess I still wonder what to make intricately-detailed hard things out of.

If your intricately-detailed things are model-like or jewellery-like solid objects, urethane casting resin using silicone moulds is your best bet. If they are more like detailed armour pieces, but there are no major undercuts and the mould can be basically 'open', you may be able to use fibreglass.

This is a total generalisation but the more detail on the piece, the more flex you may want in the mould. That said, bear in mind that a flexible mould may require backing with, wait for it, fibreglass, or plaster. :) (A 'blocky' sort of poured silicone mould will often be rigid enough on its own, but for larger shapes where you paint the silicone on in layers, you will need to give it a rigid jacket in order for it to keep its shape.)

1. If I only plan to make 1 of whatever it is, is it even worth it to make a mold and cast something?

Not if your original is durable enough for use.

2. Then again, it sounds like for some pieces, that would really be the only way to make something light and strong enough to be wearable. No?

Don't see why. You can always fibreglass the outside of something, then putty and sand it smooth.
 

stormtrooperguy

Sr Member
RPF PREMIUM MEMBER
I think you are looking for more simplicity than is reasonable ;)

There are tons of ways to make molds and then to make castings from those molds. All of them have pros and cons, so you need to learn them all and figure out what's right for you.

Here's what I would do. Well, not really... I'd make the positive and vacuum form the copies out of sheets of plastic. But, going on the "dining room" theory I'm going to skip that notion ;)

I'd take the positive, and paint on a bunch of layers of brush on silicone like smooth-on rebound 25. For a big piece like a chest I'm guessing you'd use a couple of gallons, so probably $375ish worth of rubber. When laying the silicone make sure to put in some keys for the shell.

I'd then build a rigid shell around the outside of the silicone. I use plasti-paste, also by smooth-on. Again, I'll assume a couple of gallons, so say $200 to be safe.

When you are done, you pull the rigid shell off and set it down somewhere. Then you peel the silicone off and put it back in the rigid shell, where it will key in nicely.

Then for castings, I'd use fiberglass. Paint in a layer of resin, then carefully lay in your fiberglass cloth. Make sure not to have bumps since those will just come back to stab you. I'd build up around 1/8" thick or so, otherwise it will weigh a ton.

If fiberglass is too smelly / messy (which, in a dining room, it would be) you could go with a brushable resin like Smooth-on shell shock slow, or 65D if you are more patient.

So, it's a lot of time and a lot of money. Totally doable, but is it worth it? That all depends on how many of them you plan to make.
 

PrimoOptimoso

Well-Known Member
RPF PREMIUM MEMBER
I think you are looking for more simplicity than is reasonable ;)

Only in the explanation. I fully expect the actual doing of it to be less simple.
Here's what I would do. Well, not really... I'd make the positive and vacuum form the copies out of sheets of plastic. But, going on the "dining room" theory I'm going to skip that notion ;)
Assuming a clay (or whatever else) positive would make for a strong enough buck, I *might* be able to get vacforming done by a friend of mine.
I'd take the positive, and paint on a bunch of layers of brush on silicone like smooth-on rebound 25. For a big piece like a chest I'm guessing you'd use a couple of gallons, so probably $375ish worth of rubber. When laying the silicone make sure to put in some keys for the shell.
And here's where the truck hits the wall and bursts into flames. $375 is already very near, and in many cases beyond, my entire budget for the costumeS, plural (mine and my girl's), for a given event.

(snipped the rest of your helpful process post)
So, it's a lot of time and a lot of money. Totally doable, but is it worth it? That all depends on how many of them you plan to make.

I'd say 10 times out of 10 I am only going to make one, wear it once - OK, maybe twice, and then move on to the next. But I want that one to be as good as it can be while still being made by my own hands.

Guess I know much better what I'm up against now - but it saddens me to be reduced to foamies and hot glue when there's so much better out there.
 

PrimoOptimoso

Well-Known Member
RPF PREMIUM MEMBER

aron42486

Well-Known Member
I'm learning about the mold/cast process as well. It seems that you want to be able to cast high detail in armor pieces that you will only need to make 1 cast of.

Silicone rubber is an excellent material to create a mold with. It offers high level of detail and is strong enough for multiple pulls (say if you were trying to create a run of items to sell in the JY). The downside is that liquid silicone rubber is very expensive for this reason.

If you are wanting to only cast one piece, then you would want a cheaper, less durable material. Materials like plaster and resin are far cheaper alternatives. If your piece is highly detailed with lots of little shapes, grooves, etc then you will have a difficult time removing the mold from the master without destroying something. The silicone rubber would simply peel off, something you cant do with a hard mold material. This might mean that you would have to carefully destroy your master in order to remove it.

For casting materials the more expensive stuff seems faster and easier to use. Smooth-Cast 65D is around $70 by the gallon. Its strong and easy to mix but gets pricey. Fiberglass and resin are cheaper but messier and more time consuming. There are numerous materials that are different in price and result. Just keep researching.

BTW, I am still learning about this so if any of the info that I have said is wrong I appologize.
 

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