Sunday, August 21, 2011

How To: Simple Resin Casting.

Recently, I've fallen into home casting.  Its simple and fun and brings the hobby around 360 degrees for me.  I make, paint and play with my own stuff.  I like making my own bases for my armies or my own vehicle doors or whatever else is interesting to spice up the army.  I really want to share my experiences so far on how I cast things like bases and vehicle doors.  

Recon at MI40k asked me back at adepticon if I could sculpt him some doors for his DYI marines.  I told I would and proceeded to just not do it...for a long time.  Finally, I came to terms with the fact that I agreed to do something and have been super lazy about keeping my word so now I'm going above and beyond for him to make rhino doors for all his stuff.  
Making your Door

Here is the door I did for Recon.  I have another in the opposite direction for the other side of the tank, so that both lions are facing forward.  The way I made the lion is really simple.  I used some thick plasticard, maybe 1/16 of a inch, and printed out a sheet of the lions on mailing address labels.  I cut out the tail, two unattached arms and body from separate stickers so I didn't have to worry about the fragile pieces being broken or have to work in very difficult tight areas on the design.

After the lion is all cut out and cleaned up, I just glued it in place on the rhino door.  If you're planning on doing this, a tip I have is to be sure not to use tons of glue because it'll squeeze out from around your design and leave a bead around it that makes it look....well...glued on.  Another tip is to get a pair of fine hobby tweezers.  If you look back to the loose chain tutorial I did you'll see the type of tweezers I use.  Getting it perfect is crucial because any mistake you make is going to be multiplied through you're entire line of doors as you cast.  Use a spare sticker to make sure the design ends up straight and centered on your door.  Take you time!

Once the master door was made, I glued it down to a piece of scrap plasticard and glued walls around it to make a little box for it.  It doesn't need to hold water, but does need to be reasonably tight.  Make it as small as you can, but leave at least 1/8" to give your self an area to pour the rubber on, but still small enough not to waste rubber just filling extra space.  The first one I made was the back rhino door on my night lords rhino and I made it in a circular lid that used maybe 8 times the amount of mold material it actually needed.

Pouring the Mold

The kit I use for casting is the oomoo smooth pour kit.  Its not super cheap, but its not really that expensive for what it might allow you to do.  The kit comes with everything you need and is pretty quick shipping, arriving in about 4 business days.  You can buy the resin set and the mold making sets separately, but to buy both at the same time is a few dollars more than the kit and you don't get an mold release.

The pouring material comes in two jugs, the rubber and the activator.  The pink is super thick, where as the blue is pretty runny.  It says to shake the pink well before use, but good luck, I've tried and never really gotten it to move in the bottle but at the same time, haven't had any problems from not shaking it.  I do give the blue a good shake just because it is watery.

The instructions for the mold material is a 1:1 ratio, meaning however much pink you use, use just as much blue.  The way I do this (the instructions recommend weighing it) is I use paper bathroom cups.  I picked up a box of 500 for around $5, the best mixing cup deal I could find.  I also like the paper cups because unlike plastic cups which require a sharpe to mark on, I can mark on them with a fine tipped pen or sharp pencil to make sure my levels are precise and accurate.

The way I do this is mark on cup a little higher than I actually want.  I marked this cup way way way too high just for demonstration purposes.

Then stack the marked cup into an unmarked cup and hold it up to a light so that you can see your mark.

Mark your cup, then repeat with the second cup.

And you'll have two perfectly marked cups.  After that just pour the pink in one cup and the blue in another.

 Pouring your molds for the first time will show you how bad you are at estimating volume.  For this mold, I filled each cup to the top of that shadow line on the bottom of the cup and still had a little more than I needed.  My philosophy with it is the same as working with Green Stuff; However much you think you're going to use, even if its a conservative guess, use just a little bit less.  I wasted so much rubber from my first kit because I way over shot how much I needed.

Now that you have your two cups poured and ready to mix, grab out your mold release and give the sculpt two quick sprays.  After that, take an old brush you don't care about and brush around the sprayed release agent.  This takes about 5-10 minutes to dry or more depending on how soaked you made your sculpt. You could obviously do this even before you mark and pour, but its generally at this step that I remember to spray my sculpt so this is naturally when I do it in my own process.

When I mix the rubber I pour the blue into the pink.  I do this because the blue is way more runny and easy to get out of its cup and into the pink cup.  When doing very small amounts like this I usually pour just a smidgen more blue to account for what gets left on the walls of the cup, even after a good scraping.

After you get the two into the same cup its time to mix.  For this, I use kabob skewers.  I had a ton of them in my kitchen and I like them more than popsicle sticks for mixing.  I just cut them in half and go to work.  When mixing, you want to make sure to get a nice even purple color.  The instruction book has a pro tip that once you think you're done mixing, mix for 3 or 4 more minutes.  That's been spot on for me in the past were I've mixed, thought I was done, remembered this tip and while I was mixing this big glob of blue shows up that was somehow protected in a corner.  The rubber has a working time of about 30 minutes, so usually I mix the rubber for about 5 or 6 minutes and then roll it around the edges of my cup for a few more minutes to get as many bubbles out as I can, like a cement mixer does with cement.

But, try as you might, there are still going to be bubbles.  So, after tapping the cup on my desk, cement mixer'ing and tapping some more the last line of defense against bubbles is the long pour.

When you pour, make sure you do a few things.  First being that you pour from a good 8 or more inches from your sculpt.  Second, make sure its super slow and you get this long string of rubber.  This makes the rubber so thin that the bubbles come to the surface, stretches the bubbles and breaks the tension on them, causing them to pop.  Lastly, make sure you pour into a flat, non-sculpt occupying area and allow the rubber to roll over what your casting, like lava flowing over stuff.  All these steps help to eliminate bubbles and makes sure the rubber settles into the cracks and crevasses without trapping air.
After its poured I tap it to try and free any bubbles as a last line of defense.  I'll tap it flat on the desk or rap on the sides, and bottom with a pencil just to try and knock as many bubbles loose as I can, and I usually see a couple dozen come up, despite all the effort and steps to prevent them.

Now, as a side not for the troll that might read this, yes, you can get a vacuum chamber for a few hundred dollars or make one at home (please don't, you might die) but to me, that a big investment and unless you're looking to cast a ton, a few bubbles aren't going to matter.  But, it is valid that there is a lot of extra equipment that can help with bubbles by either decreasing or increasing pressure.  These have a bigger impact on resin when bubbles can get tricky to eliminate in more complex molds.

So there, your mold is going to be ready in about 5-8 hours.  Its usually ready in 5, but not completely set until 8 or more.  Be patient, its a lot of work to make your molds.  Don't ruin them by casting in a soft mold because the resin can pull rubber off when you take it out of the mold.

After a trip to the in-laws and about 8 hours later, here is my mold.  This one was pretty simple and came out clean.  I just go around with my tweezers and pull off extra rubber like those two little spikes on the right side of the mold where the rubber went between the glued down door and the plasticard.

As you gain experience you'll recognize where air will trap when you're casting.  In this, I saw some rubber went under the finger tips and smaller details of the lion so I just tweezed out the rubber because air would definitely get trapped in there.  The only other thing that went wrong with the mold was when I glued the door down, some glue squeezed out by the hinge and I didn't notice it and is now part of the mold and will be reflected in the cast.  Its not a big deal, just means the casts will require more trimming and that is going to increase the risk of breaking something off since resin is so much more fragile than plastic.

 Pouring Resin

With pouring your resin you do basically the same steps.  Like the rubber, this is a two part epoxy that has a 1:1 ratio.  The difference is that the resin has a working window of about 4 minutes and sets in 10-15.  That means you really need to have all your supplies around and mold ready because once the epoxies hit, the timer starts!

The way I measure my resin is with syringes.  I used to work at a pharmacy so they don't look at me funny when I come in and say "Hey, Amanda, can I get like 25 of those syringes we give to parents to give their kids meds?" But, I'm confident that you can ask your pharmacy because they get boxes and boxes of thousand of them and shouldn't care to give you 10 or so.  Just make sure you point out you're looking for the needless ones and don't look/act like a strung out heroin junkie.

To help keep things straight, I marked off the syringes  using a blue and yellow rubber band so I don't accidentally mix them up.  Also, In my experience, if you're off by even just an ML in your ratio, it won't set up right and will ruin your mold.  I've lost a few when I was rushing myself and forgot how much of the blue I pulled up.  The resin will eventually after a day or so harden but it will stick like super glue to your mold.

If you do realize you've messed up the mix (a good sign is if it doesn't set up within 10-15 minutes) what I've gotten to work is to suck up as much as I can out of it and then mix up a new correct batch and pour it in the mold.  It'll set up and pull up some of the bad mixed resin.  Throw the cast away as its usually not usable and repeat.  It took me about 3 or 4 times but I was able to get all the bad mix out and save the mold.  The resin is not water soluble so you can't just wash it out, and when I did try it just made it harden almost instantly and destroyed the mold.

So, once you have the drawn up, mix them in another cup again with the skewer, suck up the mix and slowly pour into your mold again allowing the mix to slowly roll over your mold to prevent trapped air.

Your resin syringes can easily be reused as well.  First I carefully scrape the resin off the outside once its hardened.  Then I remove the plunger and use a needle clay working tool to push the resin plug back into the syringe body and out the open end.  After that it can be reused.

So finally, here is our finished product.  Pretty simple and really adds a uniqueness to your army.

Happy casting and as always, if you have any questions feel free to post; good questions and comments are always welcome!


  1. GReat post! been looking at getting into resin casting for some time now to save myself some cash and to make lots of copys of all those things boxes only come with 1 of. could you try to do a 3-d object like a melta gun as a quick tutorial
    would be most appreciative

  2. At the rate I paint at you had another 2 years before I came looking for the doors!

    Cant wait to get my hands on them, seriously they look awesome.

  3. Fantastic tutorial, thanks for the effort you put in as it makes the whole process look much less daunting. It has provoked my curiosity and I will have to look into this. Good work sir.

  4. I started resin casting making jewelry so switching to war hammer parts wasn't too hard. This guide is good and simple for new people. Also people always ask me to make things for them and it takes me FOREVER hahaha

  5. Yeah. I really don't mind doing for friends but it rides on a knifes edge. On one hand its great to have a variety of bits available but on the other it takes away from the majesty of a 'true' gw army and that persons, personally...i would say foolish, work in buying a ton of bits.

    I would also agree that people dont realize the amount of time and materials it can take to make a 3d mold. I'm still wavering about making a guide for that, but it takes a long time and when your hobby time is already budgeted (parenthood rocks!) its hard to devote that large of a percentage to someone that might think I'm more of a friend to them then I really am (looking at you OST, you SDMF).

  6. Parenthood is indeed pure awesome win!

    Sure does cut into your hobby time though. I figure you only cast those things which are going to save you time in the long run. I usually stick to bases, markers and doors. They're all quite straightforward. I've tried some 3d bits like a custom turret for my razorbacks but it was more time and effort than I had hoped.

    Projects like this one are ideal though.

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