Plaster as mother mold?

[FinnishSpartan]

Okay guys,

I was just wondering if you could use plaster as a mother mold instead of Plasti-paste? (either plaster or plaster cloth)
It would save me about 80 dollars in moldmaking supplies.

I'm using smooth-on rebound 25 as the silicone mold.

-Finish

 

[Ral Partha]

In a word, yes. A lot of people use plaster for mother molds.

 

[FinnishSpartan]

In a word, yes. A lot of people use plaster for mother molds.

Thanks,
This will save me alot of money, wich will allow me to buy more casting materials.

-Finish

 

[SGT V]

It will make slushing the resin a little harder but it would work. Get some burlap to embed in the plaster to give it some extra strength because the pulling apart when you take the piece out will cause a lot of stress on the plster. If you can get Ultracal 30, it is a good plaster for mold making and with burlap reinforcement embedded in the mold will give you a really strong mother mold.

SSG V

 

[AoBfrost]

People use it all the time for stormtrooper armor and other armor/props, just be sure like silicon to brush on a few layers before you pour it all on, you want to capture as much detail as possible.

 

[FinnishSpartan]

People use it all the time for stormtrooper armor and other armor/props, just be sure like silicon to brush on a few layers before you pour it all on, you want to capture as much detail as possible.

These materials are all i need right?:
33221-1007
PRIMA PLASTILINA, 2LB

In stock and reserved!
$7.29

$7.29
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To Wishlist
33524-2009
SMOOTH ON, 2/PK 32OZ CAST 300

In stock and reserved!
$18.67

$112.02
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33586-1009
SMOOTH ON RUBBER, REBOUND 25 PINT KIT

Item is backordered.
$27.30

$81.90
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To Wishlist

+plaster

 

[AoBfrost]

Not too sure about smooth on products with plaster, all I know from my own experimenting, all I used was plaster of paris (all my hardware stores sell) vaseline as a release agent, and whatever you are going to use as the main cast.

 

[izzysenyrc]

I have a helm (obvious) and have been wondering the same thing,

if I mix up some plaster of paris and coat my helmet with it how would I remove it and what not?

I only use pep never used anything else. oh... and I have an 8lb jar of p of p

 

[Nicktendo]

I have a helm (obvious) and have been wondering the same thing,

if I mix up some plaster of paris and coat my helmet with it how would I remove it and what not?

I only use pep never used anything else. oh... and I have an 8lb jar of p of p

He's talking about using the plaster for a mother mold, not the mold itself. Don't coat your helm in plaster. It won't work unless it has zero details as well as no undercuts.

 

[FinnishSpartan]

He's talking about using the plaster for a mother mold, not the mold itself. Don't coat your helm in plaster. It won't work unless it has zero details as well as no undercuts.

Yeah, the helmet is way too detailed for that, i would use the plaster as a mother mold (and frost i'm not going to buy smoothon plaster, i'm just getting it from my local store)
You would have to make a multi part mold... 5 parts or something...

And it would actually be possible to cast Ar's using plaster. (they dont have any undercuts). I have been thinking about that.

-Finish

 

[AoBfrost]

Actually plaster can capture lots of detail:

This here was molded from plaster, and is made of solid plaster

 

[FinnishSpartan]

Actually plaster can capture lots of detail:

This here was molded from plaster, and is made of solid plaster

I do know that, it's just that if you have undercuts it wont work...

-Finish

 

[Deadguy]

I do know that, it's just that if you have undercuts it wont work... without using a multipart mother mold

-Finish

Fixed that for you..

There's no reason you can't make a rubber surface mold that's backed-up by a plaster mother mold, just be sure to make the surface mold thick to allow for compression in-order to get pieces out of mother mold area if there's anything that "projects"(causes undercuts).

The easier way is to ensure that the rubber area has no undercuts/projections, so it's easily separated from the mother mold BEFORE actually coming off the part, then there's no need for multipart molds or allowance for potential compression issues

Best of luck!

 

[FinnishSpartan]

Fixed that for you..

There's no reason you can't make a rubber surface mold that's backed-up by a plaster mother mold, just be sure to make the surface mold thick to allow for compression in-order to get pieces out of mother mold area if there's anything that "projects"(causes undercuts).

The easier way is to ensure that the rubber area has no undercuts/projections, so it's easily separated from the mother mold BEFORE actually coming off the part, then there's no need for multipart molds or allowance for potential compression issues

Best of luck!

... sorry, but i said that earlier:

Yeah, the helmet is way too detailed for that, i would use the plaster as a mother mold (and frost i'm not going to buy smoothon plaster, i'm just getting it from my local store)
You would have to make a multi part mold... 5 parts or something...

And it would actually be possible to cast Ar's using plaster. (they dont have any undercuts). I have been thinking about that.

-Finish

 

[Deadguy]

... sorry, but i said that earlier:

No need to be sorry.

In the statement I quoted, you didn't mention it, so I was just pointing it out.

I saw your other post, but since it didn't mention the compression thing, I figured I'd bring it up.

 

[izzysenyrc]

He's talking about using the plaster for a mother mold, not the mold itself. Don't coat your helm in plaster. It won't work unless it has zero details as well as no undercuts.

This is my hel from when halo first came out. it has 0 detail. no plans or anything just some flat pieces of crap

 

[gamerguy55]

This really doesn't have anything to do with plaster but I didn't want to start another thread for it.

Can you make a mold after you paint the original, or will it ruin the paint?

Sorry for the OT but I've been working on some things that I don't want to finish until I know if it will be worth it. Thanks!

 

[AoBfrost]

If you mold using silicon, I'm pretty sure it doesnt ruin the paintjob, but you may have imperfections from the paintjob, like a small glob of paint will show up in the silicon.

If you mold with plaster, you will probably ruin the helmet, because it'll have white specs and release agent on it for a long time.

 

[Walter Spase]

If you mold using silicon, I'm pretty sure it doesnt ruin the paintjob, but you may have imperfections from the paintjob, like a small glob of paint will show up in the silicon.

If you mold with plaster, you will probably ruin the helmet, because it'll have white specs and release agent on it for a long time.

Silicone may not ruin your paint job....
but it can pick up and remove any loose paint from the surface...
i.e. around edges and spots that had surface oils under the paint causing it not to stick properly...
But if you are molding, I assume you intended to use the pulls as your actual helmet, in which case why paint the original, just shoot it in primer and mold it....
Any paint that comes off and sticks to your mold will isn't a big deal either... just cast a helmet, your first cast will clean out that mold pretty well.

 

[gamerguy55]

If you mold using silicon, I'm pretty sure it doesnt ruin the paintjob, but you may have imperfections from the paintjob, like a small glob of paint will show up in the silicon.

If you mold with plaster, you will probably ruin the helmet, because it'll have white specs and release agent on it for a long time.

Silicone may not ruin your paint job....
but it can pick up and remove any loose paint from the surface...
i.e. around edges and spots that had surface oils under the paint causing it not to stick properly...
But if you are molding, I assume you intended to use the pulls as your actual helmet, in which case why paint the original, just shoot it in primer and mold it....
Any paint that comes off and sticks to your mold will isn't a big deal either... just cast a helmet, your first cast will clean out that mold pretty well.

I don't plan on using plaster, I'm gonna go with the stuff that most other people use, just because I don't want to risk screwing something up just because tried something new.

I guess I didn't really think the whole mold thing over very much. lol I was thinking that I would be using the original for things other than making casts.

Thanks for your help!!