Laser Mine model

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Lflank

Well-Known Member
I needed a prop for a laser security mine for a fan film (similar to the mines in AVPR), and was knocking around with a lump of clay just to see what proportions etc looked good, and here's what I came up with:

5558746699_d3cdaaeb7d.jpg


The more I look at it the more I like it--it doesn't have the straight edges that the AVPR model did, but I like the "organic" look that gives it. So I think I'll go ahead and paint it up.

But because it's just made of clay, it's very delicate and I don't want to break it, so I'd like to somehow make a cast of it. And alas the only experience I have with anything like casting was when I was a kid and used to make casts of animal footprints by building up a little paper dam around them and filling it in with melted candle wax.

So I'm looking for a cheap disposable method (preferably from commonly-available stuff--I don't want to go ordering professional-level stuff yet until I have half an idea what I'm doing with it) of making a couple casts of this. What I've brainstormed so far is using Home Depot silicone to make a mold and then using liquid latex to fill the mold, or maybe using plaster of paris to make a mold and filling that with Home Depot silicone.

Would any of those have any chance of working reasonably well, or am I just wandering totally off into the woods here?

I don't really need a sturdy permanent mold because I'm only going to make one or two casts of it.

Any help is appreciated--I'm utterly a rank amateur at this.
 

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MasterAnubis

New Member
The silicone method may work for you. I've used dollar store silicone adhesive for a lot of molds. None of them were caulking. The only issues I've had where when it actually adhered to some of the pieces I wanted to mold. Mainly I think it was a mechanical adhesion to the rougher castings in urethane. You may have the same problem with silicone adhesive or caulking. Is your clay air dry? If so you should test it but I don't think it will come out as well as you want.



This is how I do it:
Start with a thin beauty coat and let it cure fully overnight. I like using clear because it helps to see any air bubbles and flush them out. I use a homemade sculpting spatula for the application. If the first layer is rushed then the deeper spots will not be cured and you lose detail. Then you can lay on thicker coats but they need to cure fully too. This can take a while but I've had really good results for some prototyping parts that I didn't want to use my PlatSil on. My best molds were off of clay sculptures.

Examples:
1-6cast1.jpg


Quinnsmold-1.jpg


Looking at your model, I'd say you'd need to worry about the space between the tacks and the convoluted tubing because you may have a physical lock. You may consider filling it just a little so that you can get the mold off. I'd put it on something flat like plastic or corian so that you have a clear edge on it (like my bottom example). When your putting the last layers on take a look at it from the side and make sure your building it up the same and have the top about level. You'll be flipping it over and it will need to be level to hold the liquid your putting in it. This should be great for plaster(or better Hydrocal/ Ultracal). But will work great with urethane resins too.

If your using plaster, be sure to vibrate the mold to reduce air bubbles.
 

Lflank

Well-Known Member
The silicone method may work for you. I've used dollar store silicone adhesive for a lot of molds. None of them were . The only issues I've had where when it actually adhered to some of the pieces I wanted to mold. Mainly I think it was a mechanical adhesion to the rougher castings in urethane. You may have the same problem with silicone adhesive or caulking.

Looking at your model, I'd say you'd need to worry about the space between the tacks and the convoluted tubing because you may have a physical lock. You may consider filling it just a little so that you can get the mold off.
Ooh, I hadn't thought of that. The tacks are coming out (I can always poke tacks into the finished piece, and I can't use green anyway because I shoot against a greenscreen). But the corrugated tubes might be a problem, and, although it's not very easy to see in the photo, the whole piece has lots of little hole things poked in it to give it a kind of "skin" texture. So maybe the silicone thingie won't work for that after all . . . but the holes are at least wider on the outside than the inside, so maybe they'll come out OK anyway?


If your using plaster, be sure to vibrate the mold to reduce air bubbles.

I'm guessing I'll run into the same problem with plaster though too--it might be hard to get the mold off. But the plaster's not even flexible like the silicone would be, so it'd be even more difficult, no?

Maybe I need to rethink the shape I am using . . .

OK, I'll try adding a little more clay to seal up the gaps around the corrugated tubes and get a smoother joint between them and the clay. This whole "sculpting" thingie is entirely new to me, too. I never considered myself all that artistic.

(head in hands) Ohhhh, what have I gotten myself into . . .? ;)

Well, if I give the silicone a shot, it won't physically bond with the clay, will it? The worst that'll happen is that the mold will rip as I'm taking it off, and I'll have to pick little pieces of silicone out of my clay piece, right?

Sorry for all the (what may be completely dumb) questions. This is all completely new to me. But I'm eager to learn. :)
 

Lflank

Well-Known Member
Oh, hang on, I think I am confusing myself here---I think you are referring to using plaster as the casting agent, inside the silicone mold---and I think I misinterpreted that as referring to using plaster as the mold. If so, I think I am unconfused now.

How would making a silicone mold and then using liquid latex as the casting agent work out? I'm afraid that if I make the cast itself out of plaster it'll still be more fragile and undroppable than I'd like.
 

MasterAnubis

New Member
Oh, hang on, I think I am confusing myself here---I think you are referring to using plaster as the casting agent, inside the silicone mold---and I think I misinterpreted that as referring to using plaster as the mold. If so, I think I am unconfused now. ;)
Yes. :devil:

How would making a silicone mold and then using liquid latex as the casting agent work out? I'm afraid that if I make the cast itself out of plaster it'll still be more fragile and undroppable than I'd like.
Is your clay still soft, what kind is it?




I'm not saying a mold can't be done the with the tacks in place, it just wont be what I'd recommend for your first cheap mold.

The tubing would only be an issue at the ends if it's not sealed. The silcone would go into it and you'd have a lock and my have issues with taking it apart. I'm just going off of the photo and can't tell for sure if the ends are closed up. The caulking is pretty thick and won't act like the silicones we use for molding and this may not even be an issue. I may just be over thinking it.

With the shape of your sculpture you may not have a problem with making a plaster mold of it to make a latex version(provided your clay is soft). But long story short... silicone is not a suitable mold for latex.

I've found that the deep texturing is only an issue on harder object or if your impatient with the beauty coat.
example:
This head I cast with a silicone adhesive mold. I was impatient with the beauty coat and got incomplete details(see the eyes):
head3.jpg


example:
This head(on the left) I did patiently and got perfect detail transfer:
damaged1.jpg


I'm trying not to repost all my pics :) but I think they're good visuals. Keep in mind that the originals are done in a non sulfure oil based clay.

We may be making this more complicated than it needs to be too.
 

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Elkman

New Member
Here's what I suggest: Get a pourable silicone starter kit from Smooth-On. You can find one at a well-supplied art store, or you can buy one online. It costs about $50, and it'll contain everything you need to make a mold of your mines. The kit contains a two-part pourable silicone where you mix part A and part B, then pour the silicone over your sculpture. After you've made the mold, you can make the plastic casts by mixing part A and part B of the plastic. It's reasonably easy to do, and when you're done you'll have a new skill.

The pourable silicone is flexible enough that small undercuts won't cause a problem -- the rubber will flex when you remove your original sculpture or your newly-cast piece. It'll also create a very accurate replica of your original. I don't know if the silicone caulk method works quite the same way. In theory, it should, but I don't know if the individual beads of caulk will unite together and lay flat against the original.

As far as casting latex into silicone goes, the usual rule is that if you're making a solid cast, you need a flexible mold. If you're making a flexible cast (like a latex mask), you need a solid mold (like Ultracal 30). Flexible against flexible wouldn't be as much of a problem as rigid against rigid, but I'm not sure if the latex would cure with the kind of skin that you'd get with a hard mold.
 

Lflank

Well-Known Member
Is your clay still soft, what kind is it?

Sorry I didn't answer that before: it's some "self-hardening clay" that I got in a craft store. It is completely air dry--no longer even cool to the touch. I didn't think much about the clay because when I first began shaping it, I wasn't actually planning on making a cast from it. So if I messed that part up I'll chalk it up to experience and make another model from a different clay. Is there a particular clay that I should look for?


I'm not saying a mold can't be done the with the tacks in place, it just wont be what I'd recommend for your first cheap mold.

The tubing would only be an issue at the ends if it's not sealed. The silcone would go into it and you'd have a lock and my have issues with taking it apart. I'm just going off of the photo and can't tell for sure if the ends are closed up. The caulking is pretty thick and won't act like the silicones we use for molding and this may not even be an issue. I may just be over thinking it.
There was a little bit of gap at the ends of the tubes, but now I've sealed them up with more clay, and also run a little bit of clay along the bottom edges of the tubes and blended it in so there's not so much of an overhang there.



With the shape of your sculpture you may not have a problem with making a plaster mold of it to make a latex version(provided your clay is soft). But long story short... silicone is not a suitable mold for latex.
Roger that on the latex.

Sounds like if I want a latex casting I'll need to make a new clay model from a non-drying clay, yes?

So for now I'll try a silicone mold and then cast the piece with plaster. Is plain ole plaster of paris OK, or is there something else I should look for?



I've found that the deep texturing is only an issue on harder object or if your impatient with the beauty coat.
OK, so I want to take my time and make sure I work the first coat into all the nooks and crannies really really well.

I'm trying not to repost all my pics :devil: but I think they're good visuals.
They are extremely helpful. And I'm extremely grateful for the help. :)


We may be making this more complicated than it needs to be too.


I'd not know, since I haven't the faintest idea what I'm doing, so it ALL sounds complicated to me. ;) But I'm reasonably bright and I usually pick things up pretty quickly.

Many many thanks.
 

Lflank

Well-Known Member
Here's what I suggest: Get a pourable silicone starter kit from Smooth-On. You can find one at a well-supplied art store, or you can buy one online. It costs about $50, and it'll contain everything you need to make a mold of your mines. The kit contains a two-part pourable silicone where you mix part A and part B, then pour the silicone over your sculpture. After you've made the mold, you can make the plastic casts by mixing part A and part B of the plastic. It's reasonably easy to do, and when you're done you'll have a new skill.


Yep, maybe the "Beginner's Box" is my best option--then I can just concentrate on learning how the process is done and not have to worry about what materials work with what.

My model is made of air-dry craft clay that I got at a craft store. Is that going to be OK for this process, or do I need to resculpt it in a different clay?



As far as casting latex into silicone goes, the usual rule is that if you're making a solid cast, you need a flexible mold. If you're making a flexible cast (like a latex mask), you need a solid mold (like Ultracal 30). Flexible against flexible wouldn't be as much of a problem as rigid against rigid, but I'm not sure if the latex would cure with the kind of skin that you'd get with a hard mold.

Got it. Makes sense now that I hear it.

Many many thanks. One day when I win an Academy Award for best makeup effects, y'all can brag that you gave me my start. Well, OK, maybe that's a tad unlikely. But many thanks anyway.
 

Elkman

New Member
Yep, maybe the "Beginner's Box" is my best option--then I can just concentrate on learning how the process is done and not have to worry about what materials work with what.

My model is made of air-dry craft clay that I got at a craft store. Is that going to be OK for this process, or do I need to resculpt it in a different clay?
That shouldn't be a problem. You'll just want to seal it before you start pouring silicone. I think they include the sealer with the starter kit, though, so you should be good to go.

Good luck, and let us know how it goes!
 

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Lflank

Well-Known Member
OK, got my molding kit from Smooth-On today. I'll try it out this weekend and post whatever happens.

 

Lflank

Well-Known Member
OK, finished making the mold. The process was actually pretty painless--just mix equal amounts of two liquids, stir thoroughly, and pour without making any bubbles. Here's a photo of the clay model and the finished mold:

5596641160_a48642a08b.jpg



The foam rubber captured every tiny detail of the model, right down to the fingerprint that I inadvertently left in the clay. Impressive.

Next step is to mix the resin and pour the casting . . .
 

Lflank

Well-Known Member
Next step is to mix the resin and pour the casting . . .

Woo hoo, success!!!!! It turned out great. :D

5596229625_de6dd977bd.jpg


Next step is to paint it up and glue my pushpins back on.

My sculpting skills are, uh, less than ideal, so it's not exactly Hollywood quality, but it'll do just fine for my fan film. I'm happy with it. :p

It's turning out to be quite a pricey piece for me, though. The kit costs $50, and I only made one mold and one cast. I got enough casting resin for probably 15 more casts, but only enough molding rubber for one more mold the same size. If I were going to be making lots of casts from each mold (to sell them or something), that'd be OK, but doing just one or two casts from each mold makes each cast piece frightfully expensive.

Since I still have the original clay model, I'm going to try making a mold from it using Home Depot silicone caulk, and then cast another resin piece from it. If that works out, then I can use cheap silicone molds for my one-offs, and just replenish the supply of casting resin whenever I need to. Seems a cheaper way to go if I'm only doing one or two casts of each mold.

Mostly, though, I just wanted to learn how to do the casting process, and it turned out to be a LOT simpler and less complicated than I thought it would be. If only my sculpting skills were better than they are. Perhaps they'll improve with practice.

So I think next I'll cast a set of teeth for my modified Rubies mask. :)


Thanks to all for the help everyone offered, and sorry for all the dumb questions I asked. It wasn't near as difficult as I was afraid it was gonna be. ;)
 

Lflank

Well-Known Member
I did have one difficulty that I had to work around. If you look closely at the casting, you'll see a narrow little "lip" around the edge that isn't there in the clay model. That's because when I made the model I didn't make it flat on the bottom--there was a wee bit of wavy edge all the way around it. So, since I didn't want any of the rubber mix to get underneath there when I made the mold, I had to add a little rim of clay all the way around, and mash it down tight against the bottom of the mold box.

Worked. :D
 

Elkman

New Member
:D I'm glad to see everything worked out well for you. Welcome to the world of moldmaking and casting. (Wait, doesn't the Smooth-On box already say that?) I told you it wouldn't be all that difficult. Unfortunately, as you've figured out, silicone is pretty expensive stuff, so you'll probably need to decide what works best for each individual project you're doing.

Oh, and tell us how the silicone caulk method works out, as compared to the pourable silicone method. I'm kind of curious to hear about it.
 

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Lflank

Well-Known Member
:p I'm glad to see everything worked out well for you. Welcome to the world of moldmaking and casting. (Wait, doesn't the Smooth-On box already say that?) I told you it wouldn't be all that difficult. Unfortunately, as you've figured out, silicone is pretty expensive stuff, so you'll probably need to decide what works best for each individual project you're doing.
The difficulty is that I'm only making one or two casts per mold, so the price per cast is a lot higher than it would be if I were doing lots of casts from each mold. I'm hoping the cheap silicone caulk molds will at least hold up long enough for one or two casts. That's all I need.

Oh, and tell us how the silicone caulk method works out, as compared to the pourable silicone method. I'm kind of curious to hear about it.

I'll post the results, for better or worse. :D

The level of detail with the pourable silicone rubber is fantastic, so I doubt that the caulk method will be able to match it. But since I'm just using it to make props for fan films, I can live with a bit less detail.

We'll see what happens with it.
 

Lflank

Well-Known Member
Pulled a cast from the silicone caulk mold today.

The way I made the mold was to put a thin layer of caulk over the model and using my finger (coated with liquid soap to prevent the caulk from sticking) to push the silicone into all the nooks and crannies in the mold. After that layer dried, I added several more layers (allowing each layer to dry) until the caulk was about half an inch thick all the way round, then let it dry overnight. I didn't use any releaser or sealer on the model, but since I had already cast a rubber mold from it two days before there may have still been some sealer and releaser adhering from that. In any case, the mold peeled away from the model pretty easily:

5601766870_55503df4fc.jpg


The next difficulty I ran into was how to make the mold sit properly so it would be level. I solved that problem by placing the mold into a dish filled partly with uncooked couscous (pasta made into very small balls), then filled the mold with water and adjusted its position by moving it around in the dish until the water sat level with the top of the mold:

5601182569_266b50a683.jpg


Once everything was set up nicely, I used some paper towels to sponge out the water and let the mold dry completely before mixing and pouring the casting resin.

Here are the results:

5601767574_b8e2de8ba0.jpg


The cast piece on the left was made with the pourable silicone mold; the cast on the right was made with the homemade silicone caulk mold.

The piece that was cast from the caulk mold is a little narrower because I didn't make the little clay dam around the edges that I used with the pourable silicone mold.

The caulk mold was not damaged or torn during demolding, and it looks like it could certainly be used again.

Looking at the two casts side by side, one can see that the silicone caulk mold, while not as sharp or crisp as the pourable rubber mold, still did a pretty good job of capturing detail.

Some flaws are apparent, though. The edges are noticeably rough--that is because as I noted before the edges of my model were not flat, and I did not make the temporary clay dam with this mold that I did with the pourable mold (I assumed that the caulk would be so thick that it wouldn't flow very far into this gap.) There are also a number of long thin raised lines in the caulk-cast piece--they look like they are the result of "seams" between the beads of caulk that I didn't get when I used my fingers to smush the caulk smooth against the model. Those would presumably not appear if I practiced a bit and got better at smoothing out the caulk.

So my conclusion is: while not Hollywood level and not as good as the pourable silicone mold, the homemade caulk mold worked pretty well and did a pretty good job at capturing detail. Not good enough for pieces that one wants to sell, perhaps, but good enough quality for use as a fan film prop. The only flaws I see in the finished piece are apparently just the result of my inexperience, and should disappear with more care and practice.

I think it's a quite viable option for people who want to make just one or two fairly-detailed casts from a cheap disposable mold.
 

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