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Anyone experienced with casting?

I'm trying to use Instant Mold & Milliput Superfine putty to make some Space Wolf backpacks (with wolf head exhausts).

Milliput sticks to the mold and the shape gets ruined when I try to separate it. Do I need to wait more than 4 hours? Maybe oil the mold?

P.S. I tried using Alumilite resin, but after adding Alumilite resin dye to Side A, the resin mix always bubbles up. It worked fine before I added the dye. So that's a whole bottle of Side A resin trashed.

I've heard Oil based putties stick to molds, don't know more than that. Stir the resin thoroughly before adding it to the moulde, the bubbles will form and you can stir them out.

If you wet the mould with water before adding the putty it should be fine. That's what I do and have not had any problems with it sticking.

For fine details you will want to let the putty cure fully before attempting removal. How long that takes is dependant on the ratio of the mixture of the two halves of the milliput. 1:1, properly mixed, should be pretty solid after a couple of hours.

Also, be careful with how the instant mold interacts with the details of the part. If it folds over an edge it will "grip" on more and that part will be more difficult to remove.

Consider cutting the instant mold away from the cast, as it can (if it's anything like the Oyumaru I have) be stuck back together to make a new mould.

shauni55 wrote:
I've heard Oil based putties stick to molds, don't know more than that. Stir the resin thoroughly before adding it to the moulde, the bubbles will form and you can stir them out.

By the time the bubbles form, the resin is too stiff to pour into the mold. I think I got a bad batch of dye, as I didn't have this problem before mixing it in. I know I'm using the right mix of A:B since I have two separate syringes I use to dispense exact amounts into the mixing cup.

What does get ruined? The mold? The Result? Ive done a few pressmolds myself and I never had problems with separating. (But that's probably due to me letting them cure overnight. )

This is what I normally do with pressmolding:

1) Build a cage with lego and put the heated instant mold inside. This helps to avoid distending the mould.
2) Press the part inside with the goal to form a decent mold line. This often needs adustments to get a tight fit around the copied parts sides. Don't forget to add a few pokes with the backside of a brush or something. Those holes/bumps will help aling parts later.
3) Next add the other side of the mould with a lot of pressure, but try to keep it even. (Using a square shaped object helps in force distribution)
4) Most of the time the second side has the better detail coverage, so I simply redo the first side.

The resulting mould should be easy to remove and thanks to the bumps also easy to align. And the Instant mould is flexible enough to even allow some overhanging details. Its just hard to get putty into those areas. And better wait for the sape to fully cure or those details may still warp during removal.

If you fill in the mould don't fill it up completely. Too much putty results in massive mold lines, and often misalignments too. And fill both sides individually. Press the putty into each detail by hand to help coverage. Also pull it over the edges slighly, otherwise you might have holes along the sides. Only then press both parts together. You'll end with thin mold lines and additional putty will mostly be pushed inside the shape. Your result will probably be a bit hollow inside. But who cares as long as the surface is okay.

Another advice on milliput. Superfine is a bit tougher to work with. And due to its claylike consistancy will quickly stain your instant mould(All milliput types will probably do that). Standard milliput is cheaper and works better for Pressmolding in my experience. But the best results I had was with a mix of GS and Milliput standard. Alternatively you could try and let the putty cure for a bit before adding it into the mould.


But despite all this, don't expect perfect results. With Instant mould press moulding you'll seldom get all the details propperly. But the results should at least be decent enough that it will look mostly fine once painted.

And I can't help you with resin dyeing. But are you supposed to add it to one side or during mixing of both sides? I always thoughs you add it during the mixing process and not before ...

Using Insta-mold you want to give the mold a very thin coat of Vaseline or oilive oil, the greenstuff which will help prevent the green stuff from sticking.

Wait are you using the instamold to recreate the backpacks with millputty or recreating the backpack sclupted with mill putty using instamold?

if its the first try to let the putty cure over night or a day and fully harden before demolding.

I find using a little lip balm in the model works. so did water.

If the resin is bubbling it's likely due to water or moisture in the mold, make sure the mold is 100% dry as most brand of resin react with water and it causes it to boil and turn into a foam like state rather than turning solid as it cures.

 paulson games wrote:
If the resin is bubbling it's likely due to water or moisture in the mold, make sure the mold is 100% dry as most brand of resin react with water and it causes it to boil and turn into a foam like state rather than turning solid as it cures.

This^

Also...depending on how many you need, just buy them from ebay - might be a better use of your time and money.

Molding work is an art - it takes a lot get used to the nuances and techniques, for resin, press molds or what ever you are using.

Also, check out youtube, there are tons of threads on there for various casting methods.

Best of luck!