How to make a Simple Two Part Mold

Hi Folks,

Jimmi here, hope everyone’s A-OK! Today I’m going to show you how to make a simple two part mold. You’d use this to cast complete 3D objects, such as a gun. This obviously makes this far more useful than the single part mold technique, which limits you to just casting one side of an object.

That said, make sure that you’re up to speed with casting a single part mold before you begin, my tutorial last week takes you over the details so I strongly recommend that you start there and go over the basics (such as the materials, and making a Lego box etc) before you read on. Go on, I can wait whilst you read that first and then come back!

You’re back already? Great. First thing to say is that this method isn’t perfect, and you’ll struggle to cast complicated things with heavy under hanging detail, for example, if you tried to cast a full soldier holding a two handed rifle across his body, you’d probably find that the space between his weapon and chest (see below) became one solid lump of material. But for relatively simple 3D shapes you should be rocking, so guns, limbs, heads, torsos, backpacks… all should be OK if you’re prepared to put the effort in.

You wouldn't be able to cast something like this

You wouldn’t be able to cast something like this very well

Making the Mold

  1. Prepare your Oyumaru in the same fashion as you did for the single part mold, leave half of it in the hot water.
  2. Place your malleable Oyumaru in your Lego mold box

    Lego Box

    Lego Box

  3. Press your piece to be cast into the Oyumaru, you need to roughly push it in so far as the halfway point
  4. Take a small paintbrush, turn it upside down and press the non bristled end into  your Oyumaru surrounding your model. Make about 4 or five impressions. You’ll see why this is important later.

    Making the keys

    Making the keys

  5. Let this cool – run it under a cold tap for a minute or so
  6. Take the other half of your Oyumaru out of the hot water and press it over the the first half. Be careful to ensure that you capture as much detail as possible by using your back end of that paintbrush again to push into the Oyumaru, forcing it into all the nooks and cranny’s.

    Closing the mold

    Closing the mold

  7. Let this cool again- run it under a cold tap for a minute or so
  8. Remove your Oyumaru mold from the Lego box, and peal the two pieces apart. You shouldn’t have any issue with it sticking together as long as you allowed it to cool each time. Not that the two halves can easily be placed back together using those brush holes you made, which act as a sort of key.

    The completed mold

    The completed mold

  9. Remove your master from the mold


  1. The first challenge here is judging how much ‘stuff’ you need. I use Milliput, but you can use Greenstuff or other ‘Stuff‘ of your own choice.
  2. Press your ‘stuff’ into each side of the mold, trying to be as neat as possible and removing as much of the excess as you can do

    Filling the mold

    Filling the mold

  3. Close the mold together using your keys to ensure it closes perfectly. Set it down somewhere with something on top of it to keep mild pressure. Then leave it alone until tomorrow.
  4. Wake up, make a cup of tea. Drink your tea and think about your day. Consider doing some Yoga. Reconsider doing the Yoga – it’s just not for you.
  5. Carefully peel open your mold, it should be set and have captured most of the details. You might need to do a spot of cleaning though – this is easy or difficult depending on how well you judged the quantity required and what ‘stuff’ you used. This is why I like Milliput as it’s easy to work with once it’s cured!
    It's like opening a treasure chest

    It’s like opening a treasure chest

    Some cleaning will be required

    Some cleaning will be required

  6. Congratulations, you should have a fairly decent replicated bit. I’m going to stick this pistol/knife combination to my Ork Warbikers!
Not perfect, but not bad

Not perfect, but not bad

Let me know how your attempts went in the comments below. Plus, if you’ve got advice on how to improve this technique, I’m always happy to learn more, so let me know!

If you want to read more content (And frankly, why wouldn’t you!) you should check out John’s guide to making wires and hideous sanity defying monstrosities.





When you cast copies of some company’s bits, you’re generally not allowed to sell them on. That’s a breach of copyright. Here in the UK, you can take casts of things as long as it’s for personal use only.

Check your local laws if you’re in any doubt, I’m washing my hands of any responsibility!!!

2 thoughts on “How to make a Simple Two Part Mold

  1. Pingback: Wot I Think – Shadow War Zone | Jimmi Waz 'Ere

  2. Pingback: How to make a Simple Single Part Mold | Jimmi Waz 'Ere

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