Press Moulding Questions

[Primarch]

I have recently found myself in need of duplicate parts that come 1 to a box, so I figured I'd have a shot at press moilding some bits and pieces. I bought some oyumaru from Daiso and have some old green stuff and milliput lying around. (And some vallejo liquid putty, but I'm not sure how useful that will be).
Since I know some people (Konrad) are experts on all things green and stuffy, I'd like to ask a few questions before I begin.

1. Is green stuff/milliput strong enough to make the shaft of a weapon like an axe/spear?
2. Which type of putty holds detail better?
3. Can you file mould lines off green stuff?
4. Do I need to put a vent into the mould to let excess putty out?
5. How thick does the mould need to be?
6. How do I avoid getting air gaps in the mould?

[me_in_japan]

I work more with resin moulds than green stuff, but I do have some experience with it. I’m sure Konrad will be along with more detailed/accurate advice, but for now:

1. Probably, but a far easier option is buying a pack of wire from a garden/diy shop and using that. Just cast the spear head and drill a hole for the shaft to go into.

2. My “stuff” of choice is definitely grey stuff (ProCreate) mixed about 50/50 with milliput, and I believe Konrad uses the same. It has an excellent mix of stretchiness and malleability, and after it cures you can sand it.

3. No. But you can if you mix it 50/50 with milliput.

4. Not for green stuff press moulds. For resin, 100%yes. The difference is that resin fills the mould purely under the influence of gravity, so air bubbles that can’t escape are immovable obstacles to the resin. Press moulds fill the space due to you squeezing the shit out of them, so you can squidge em around and make sure they are full of putty. Because it’s a 2 part mould, there will always be small gaps between the mould halves for air to escape from. If it’s wee cavities down in the depths, just squish the Stuff in with your fingers before joining the two mould halves together.

5. Thick enough to survive a good hard press without deforming. So pretty thick. Maybe an inch or more? Depends on what you’re moulding.

6. Make sure the oyumaru is very hot. Use boiling water to make it almost semi-liquid then press your mini into it. You’ll probably have to press the edges of the mould up against the mini while it sets. Fiddling with the temp of the mini itself is also a factor. You can set the whole shebang by plonking it into a container of cold water. Then repeat with the top half of the mould.

[Primarch]

Well, I had a crack at making some oyumaru moulds, if they don't work out I can always try again.
I mixed up a bit of green stuff with some milliput and jammed it into the oyumaru. I guess I just need to wait and see how it all turns out. Worst case scenario, I'm down a few grams of putty.

[me_in_japan]

That’s the beauty of oyumaru. Good luck

[Primarch]

My first experiments have yielded their results.

Two Volkite weapons (30K death rays).

The detail isn't too bad, I think I may have overfilled the mould as the mould lines were a bit thick. There was also an air bubble on the back of the hand attached to the pistol. This should be fixable with a little liquid putty though.
They are a little bit bendy, I may try drilling a hole and inserting a metal rod?

[me_in_japan]

honestly, those look within acceptable limits to me. Not exactly boutique resin minature standard, but hey ho, once theyre painted up and on your minis, really, who's going to notice?

As for bendy, how solid do you need em to be? I've found green stuff (and its equivalents) to be fairly solid-ish. I dont know the specific yellow one youve got there, but maybe you mixed the two parts in a funky ratio? Or maybe its just a softer epoxy. I dunno *shrug*

Still, anyway, I'd call that a success. Job's a good un

[Primarch]

It's a mix of green stuff and milliput. As you say, once they are painted they should look ok.
I don't need them to be rock solid, I was just surprised that they remained a little bendy, it's my first time using putty for anything except gap filling.

[Konrad]

Mij's advice is all spot on. I'll just add if you need support , you can add the wire (brass rod if you need it real strong) before you press the two halves together. Cut a little channel in your mold for the rod if you need some rod sticking out the back to pin into your figure later or as a handle for painting. Or drill and pin it into your master part before making the mold.
Then fill and press one half of the mold with a damp tool. Lay your rod down the middle. Then fill and press the other half and then press the two halves together.
Another trick is build a mold box/frame. I use Legos. I build some wall with the Legos. Press my hot oyumaru in there with a plunger? made out of more Legos made to fit the box, to get it flat. Then I press my master bit in. Stick it in the freezer to speed up the setting. Then repeat with the top half of the mold. The walls keep the oyumaru from stretching around as you press, keeping it tighter around the master. It will help keep your mold halves square with each other when you press your parts, too.

Oh, and to add, Procreate is great for almost everything, But for press molding you probably want a Milliput/Procreate or MIlliput/Greenstuff mix like you did. Procreate does sand a bit better than Greenstuff when it cures, but Greenstuff is softer and stretchier and I suspect casts better. I have to do some more experimenting to check on that myself. So anyhow, mix in at least 50/50, or even favor the Milliput is the part is fairly solid and compact.

[Primarch]

Does anyone have any thoughts on the local putties?
My local store stocks Tamiya Smooth Surface putty for 300-400 yen and Wave (and Wave Grey) for 800-900 yen. Are they worth picking up?

[Konrad]

I've never used the Wave grey that I can recall, I just use the standard. It's identical to Milliput, I think there is even a ミリプット written on the box somewhere. I will have to pick up a couple different varieties next time. My current pack is about gone.

That Tamiya putty in a tube is dangerous stuff! Messy. Really useful only as a gap filler and even then, I'd only use it if I needed to inject a bunch of putty into a hole caulking-gun style. There are better alternatives for toy soldiers.
That being said, squeezing a big messy blob of that into a mold though.....let me know how it turns out! Might be a way to make that work!

Tamiya does make a range of two-part putties that behave something like green-stuff, but I've found to be stickier and generally harder to work with. They will do in a pinch, and for press molding, might not be a bad replacement for grey or greenstuff.