Suggestion for model making starter kit

[firespiter]

I've been looking at many of the prop replicas being crafted on these boards and have purchased two replica (resin) kits that I absolutely adore. And I have been watching "how to" videos on the staging and process. And now am inspired to try my own hand at modeling and looking to see what others might suggest to a potential beginner for a starter kit.

Initially, my thought is to try making a mold of a small part that is missing from an action figure (I have 2 action figures, but one is missing the accesory gun - someone cut it out of the pack at the store), and figure this would be a great first project, to try to make a replacement 1" x .75" gun (in resin??). Then move up to making a larger mold for another (clay model) project I have in mind and then work my way to slush cast a 10" x 10" x 10" project.

My question for the hive mind here is, can anyone recommend a place for a beginner kit. Or a list of suggested items for a beginner? I see smooth-on has all sorts of casting products, but I'm not sure what items I would purchase as a beginner. One of their "Kits" looks optimal for making hand-casts in plaster, but I *think* (and please correct my stupidity here if you can, I'm looking to make a plastic or resin replica...and that would be a different kit or purchase seperate items?

So far, I've looked at Smooth-On (as I mentioned above), and I think what I would buy would be:
Mold Star 15 (extra-long pot life for a newbie??)
Smooth cast 300 (to cast the actual new item <-probably start with the trial size)
Ease release 200 spray
Gloves
Stirrers
Mixing/measure cup
Craft wood for mold container construction (For the first item - tiny gun, I can probably use a cut-down plastic cup?).
Rags/papertowels, plastic for the work area

Do I need a respirator mask for these items? Any other needed items I'm missing/forgetting like cleaning solvents? Is there another brand/manufacturer or better product you would recommend for a potential new person?
Is the fact that I am asking these questions make me to too stoopid to try this at all?
-Terry

 

[mikoyan99]

If you're looking at starting off, can I suggest for mould making:
RTV silicone putty. It's a two part putty you mix together, 50/50, then squidge around your master copy like plasticine. It's easy to use, and gives good, detailed results. I find it very useful for casting small objects, where I don't want to have to make a mould box. In your case, I suggest you do make a small box (plasticard is the best for this) and make a two part mould with a pouring hole for your resin.

Casting wise, i've found 3 compounds are quite handy for small jobs:
Jesmonite - acrylic resin, basically PVA glue and plaster. Non toxic and water soluble, but it is prone to air bubbles. Can be brittle in thin sections as well.
Milliput - not a proper casting material, but i've found you can get quite good results with RTV putty moulds. It's a two part epoxy packing putty, again like plasticine when "wet". Makes a nice hard copy of the orginal, but can't be poured. Will take a little practice to get right, you have to guess how much you need in the mould and then "squidge" it in, closing the mould halves around it.
Polyurethane resin - two part casting resin; it's not as nasty as polyester, but still very smelly. I'd get a respirator, or cast outside if you're using very small volumes. Has the consistency of milk. Gives very good detail, and fairly strong when fully cured. I've found it very easy to use.

I don't know exactly what smooth on is, but I assume it's a type of polyurethane resin. Most of the names above are generic, except milliput. I think the closest you can get overseas (outside the UK) is plumbers epoxy filler.

Good call on the stirrers/gloves/cups etc. Will make life easier if you're using liquids. Craft wood should be find for mould construction. I use plasticard personally. Make it so you can dis-assemble the mould box, it'll make your life easier later on. I tend to re-assmble the mould box around the mould when casting to support it.

-Matt

 

[Gattaca]

Smmoth on's OOmOO is an easy way to go for silicone rubbers, you don't need to weigh it for mixing, it's a 1 to 1 mixture, and bubbles are not usually a problem. Just pour in into your mold slowely in a thin pour, not just a big glob, gives air time to be pushed out of the way. Buy small amounts to start, it has a shelf life once opened.
Good call on the smooth cast 300, great stuff. For mold release I would recommend MANNs mold release, especially for two part molds, I've had better results with it. Your mold containers need to be non-pourous or the rubber will stick to it, I usually use foam core held together with hot glue or wood that has been covered with packing tape, this gives it a nice smooth finish that the rubber won't stick to. I've been going to my local wholesale grocery store for mixing cups, stir stick and gloves, much cheaper. Our store cateres to restauraunts so lots of take out food containers from small 1 oz sauce to milk shake cups.

 

[firespiter]

This is some great advice! (This will literallyy save me a lot of money over trial and error).
I simply assumed wood would be an okay rigid form. It didn't even occur to me that the silicone would adhere to it. (slapping forehead) I do have a lot of packing tape, but I like the idea of a hot glue gun and the foam core board (I think it might be what they call plasticard in the UK).
I've seen videos (I think it was someone using a blue smooth-on brand molding material) where the person was doing a high-pour, in a very tiny stream from a good height (about 18" above the mold) to minimize air bubbles.
In the above mentioned video, the person didn't use a spray mold release. They used baby powder. Is there a reason for using one over the other? The model he was molding was a tiny mold of a head with a lot of detail.
I've used epoxy putty before, and I have a large quantity unused that I could probably try the "squidge" technique as you say. But it's expensive to use in large volumes. Might be okay for making a master of something that I'm molding.
I'm really excited about the shopping list and potential models and greebley objects I could create.
I really appreciate the advice!

I've already read on this forum multiple times about pre-stirring (shaking?) A & B parts individually before measuring them out, as being absolutely crucial. It's a step I could have completely seen myself overlooking if I hadn't read about it here first. This is all great stuff!
-Terry

 

[mikoyan99]

Foamcore is distinct from plasticard; it's handy stuff for large builds though. Plasticard is literally solid sheet plastic, usually from around 0.25mm thick to ~5mm. It's an indespensible scratch building tool.

The mould release compound depends on the material you're casting in - for example, when I cast in pewter, I use graphite. Baby powder should work, although you may want to double check in case it reacts with your resin. The grain texture may leave a very very slightly rough surface as well; if you're aiming for a mirror finish, i'd stay clear.
-Matt

 

[Gattaca]

I've never used baby powder for mold release. The spray works fine for me but don't use too much, just follow the instructions on the can. I agree with Matt, about the powder reacting with the rubber, do a test first. Also, Plasticine is useful for some applications, especially two part molds, where you press your model into it to mold one half, then the other. (see the PM I sent you). But make sure it's compatible with your silicone by doing a small test. Some Plasticine's can react with the silicone because of chemicals in it.

 

[NormanF]

Rubber:
For SmoothOn, Mold Star 15 is probably the way to go. I went to a seminar their local distributor held and they really pushed that over Oomoo. That is good for block molds. When you get to doing whatever it is you plan to rotocast you will probably want to use Rebound instead. Heck, you can use Rebound for block molds too. I almost always buy trial size of everything I get from them. I do so little it sometimes goes bad before I use it all.

I have no experience with other brands of rubber.

Whatever brand of rubber you use, one way to avoid bubbles is to use a brush to apply a thin coat of rubber to the item you are making a mold of before you pour the rubber on.

If you go the SmoothOn route be careful if you use their So-Strong tints for coloring the resin. Some of the dark ones should be called Too-Strong, at least for coloring clear parts. Also, if you use too much it will make your parts less rigid.

Gloves:
Use nitrile gloves. Some latex gloves can inhibit rubber curing. Save the latex for fiberglassing.

Mixing containers:
Another source of small mixing containers is Moe's (Welcome to Moe's!) at the salsa station if you have one in your area.

Mold walls:
Sometimes if I am in a hurry for a single piece block mold I will just use clay. I have also used cut down paper cups.

Mold releases FOR CASTING:
1 - With something like Mann spray on release you will need to wash the casting off before you paint it.
2 - Baby power can almost act like a primer and helps prevent bubbles.
3 - Technically if you are casting urethane resin you do not actually need a mold release, but it will help your molds last longer. If you cast epoxy, like I am right now for some small parts, you need to use it because epoxy is an adhesive.