Tuesday, August 17, 2010

Tutorial: Casting Resin Bases

A couple of weeks ago Drathmere posted some photos when he was casting his own resin bases for his Death Korps of Krieg army. I've been toying with the idea of trying this myself for some time, so I decided to take the plunge, and to go ahead and try to write a thorough tutorial while I do it.

The first set of bases I wanted to get out of the way were for my Ork army. I decided I wanted to go with an "urban wasteland" style, with lots of cracked concrete, debris, and rubble. The first step was to gather my materials:

...some bases with the slots filled with Green Stuff, my various basing materials, and a bag o' bitz that I bought at a convention a couple of years ago.

The bitz are just a bunch of odds n' ends - mostly marine parts and weapons. I dumped them out and started digging through them:

These are the pieces I settled on:

(Bonus: I found enough bike parts to finish a few Space Marine bikers I inherited from a friend! W00t!)

For the basic structure of the bases, I used a container of "concrete rubble" from Gale Force Nine.

To be honest, I generally don't use much Gale Force Nine stuff (I find it to be WAY overpriced), but I picked this up a couple of years ago at a convention and forgot about it until digging through some boxes in the closet last week. I have a friend who makes this himself by filling an old cookie sheet with plaster of paris, waiting for it to dry, and dropping the whole thing on the patio - that'll give you enough to last a dozen gamers a lifetime, for about 1/3 of the price of the tiny container pictured above.

Basically, I just started picking out pieces that roughly lined up, and started gluing them down with superglue. You don't want them to extend too far beyond the edge of the base, or you'll have problems with your mold later. After that, I glued down the debris where I felt it needed something:

To close up some of the larger gaps (when we make the mold, we don't want the rubber to be able to flow inside the base), I filled them with gel superglue and dunked the bases in my bag of sand:

After the glue had dried, I dripped some scenic cement from Woodland Scenics on the sand to "lock it down" permanently:

(I really like the scenic cement from Woodland Scenics - a lot of people claim that a homemade PVA/water mix does the exact same thing, but I swear that the scenic cement seems to "wick" exactly where you want it).

After everything had dried, I started inspecting the bases for areas that I thought would give me problems during casting. Here's one - there's a gap underneath this crest that was broken off from a standard bearer's pole:

To fix this, I mixed up a 50/50 mix of sand & PVA:

...then I used it like spackle, filling in the gaps:

With a little bit of paint, it will look like the crest is laying in some mud.

I have also been working on test models for my Death Korps of Krieg army and was pretty pumped about that, so I decided to make up some bases for them as well. I started by cutting up some wooden craft sticks and gluing them down to some spare bases - since I plan to theme the Krieg army to work with the Trench Outpost Box I just got from Armorcast, these will simulate the duckboards found in the bottom of WWI-type trenches:

After that, I added some sparse sand & rocks:

...then I clipped some tiny pieces of brass wire, to simulate shell casings:

These bases also got the Scenic Cement treatment:

After everything was dry, both sets of bases got a coat of black primer:

Get to the casting, already!

Okay, okay. For the casting, I purchased the Super Casting Kit from Alumilite:

The MSRP of this kit is $69.99. Now, if you start reading the DIY blogs & web forums, you'll find a lot of people saying that you can order the individual supplies in quantity, and it'll be much cheaper - and they're right. However, I recommend getting the kit the first time out for several reasons:

-It's complete. I know there have been several times that I've tried to start a project I've never tried before, only to realize I don't have something I need, and I have to run to the store, or worse, have to order something online and wait a week for it to arrive before I can start. It's INCREDIBLY frustrating. You know you'll have everything you need if you get the kit.

-You know everything is compatible. If you try to buy a lot of these chemicals online, they are sold through industrial supply houses that do not have consumer-friendly web sites - often the description is just a cryptic product code. We are working with some potentially nasty chemicals here, and the last thing you want is to blow up your house of get overcome by toxic fumes because you bought the wrong item.

-It has clear, concise instructions. The kit is really geared towards the rank amateur, and, in addition to the basic tiny pamphlet, it contains a full-sized booklet with six or seven pages of tips for getting the best results possible.

-It's readily available. This kit is available at many larger craft stores & hobby shops (I got mine at Hobby Lobby; it may also be available at stores like Michael's and HobbyTown. And, as all dedicated cheapskate hobbyists know, if you subscribe to Hobby Lobby & Michael's email list, they send out a "40% off one item" coupon every couple of weeks, knocking the price of the kit down to around $40. The kit is also available through Hobby Lobby's online store (you can use their coupons there, too) which offers flat $4.95 shipping, so you should never have to pay more than fifty bucks for the kit, if you're willing to wait until you get a good coupon.
So here's everything that comes in the kit:

Before we can cast anything, the mold has to be created first. The first step is to make a box that will contain the originals. I used some scrap pieces of foamcore I had laying around my studio. Cut out what will be the "bottom" of the box, leaving at least 1/2" between your pieces and around the perimeter. Glue down the originals with super glue:

Next the sides are added to the box. The box has to hold the rubber when it's in it's liquid state without leaking - the casting kit includes clay to seal all the edges, but I used hot glue, inside and out, to seal the box:

Seriously, you do not want this box to leak. You will have a mess of epic proportions on your hands if it does.

I then wrapped the whole box with duct tape, to add strength, since hot glue isn't the strongest bond:

Okay, now we're finally ready to mix some chemicals. But first:


Seriously, guys, we are working with some potentially nasty chemicals here, that work by means of a chemical reaction. Follow all safety precautions - eye protection, at least a mask (a respirator is better), gloves, and work in a well-ventilated area. Don't touch your eyes or your mouth when you're working with the chemicals, and wash your hands thoroughly when you're done. In addition, resin is exothermic, meaning it generates heat as it cures - while it doesn't get extremely hot, if you are pouring it at your painting desk where there are lots of flammable paints, thinners, etc., it is something to keep in mind.


Okay then. We start with the RTV silicone:

You'll notice that one of the first steps in the instructions for the silicone is to "stir well". The problem is, when you open it you get something like this:

(Actually, the above image is after about five minutes of vigorous stirring). I can almost guarantee that when you open the jar you'll think "I must have got a bad batch - this will never work!" It looks like dried-out plaster with a tiny bit of liquid floating on top. Nevertheless, grab something and start stirring. The flimsy little popsicle sticks they give you with the kit aren't gonna cut it - I used a stout-handled paintbrush, but seriously considered sacrificing an old screwdriver. Mash it up against the sides, poke it, do whatever you need to do to break up all the chunks and get it as smooth as possible. Stir it until your arm hurts, then give it to your buddy and let him stir it for a while, then take it back and stir it some more.

After it's as smooth as you can get it, add the catalyst:

Stir it rapidly until the color is uniform. You have about 30 minutes of "open" time until the rubber sets, so you don't need to rush. The catalyst will also "smooth out" the silicone a bit. After it's thoroughly mixed, pour it into the box containing your original bases:

Set the box on a level surface to dry for at least four hours.

After four hours have passed, you should be ready to "de-mold" your originals. I ran my hobby knife around the edges, then cut the box apart:

Get all the paper/glue/etc. off of the rubber, then CAREFULLY start to pry the rubber off the bottom of the box:

I was having some trouble getting the mold to pull smoothly away - I decided to bend the foamcore and break the bond of the super glue, to allow me more room to work:

This allowed me to work from the top down. The problem was that some of my "urban wasteland" bases hung over the edge a bit too much, making them difficult to take out of the mold. This actually didn't cause a problem with casting - I just made some small relief cuts around the edge of the mold. (These will tear and ruin the mold if you bend it too much, though). The two particular bases that were giving me trouble were also the ones that I was concerned were too tall - I might just cast a few of those for my HQ, and skip casting them in the future.

Most of my trench bases left their materials behind - no big deal though: I picked most of the pieces out by hand, and used my decal tweezers for the stubborn bits:

I then used a old, soft toothbrush I keep with my paintbrushes to brush the last of the debris out of the mold.

Ready to cast!

The first step in casting is to prepare your mold. You don't need the mold release that comes in the kit (that's only used if you are casting rubber-against-rubber). All you need to do is sprinkle a bit of baby powder in your mold:

...then take a dry paintbrush and "paint" the powder around on all surfaces of the mold:

Hold the mold over your trash can and gently smack it a few times to get the excess powder off:

Now we can mix the resin:

The kit contains a two-part resin, with an "A" side (the clear bottle) and a "B" side. The "B" side needs to be thoroughly shaken before pouring.

The two parts of the resin are mixed at a 1:1 ratio. Fill two of the mixing cups that come with the kit with the same amount of the two types of resin:

Pour them in a (preferably disposable) container, and mix vigorously for 30 seconds:

Once the resin is mixed thoroughly, you can begin pouring it into your mold:

IMPORTANT: You only have NINETY SECONDS until the resin hardens - THEY ARE NOT KIDDING ABOUT THIS. To illustrate my point:

I was pouring my next-to-last base when I hit the 90-second mark - in a blink of an eye, the resin changed color, and then it was SOLID. So work fast.

"But wait", I hear some of you saying, "You said to stir the resin for THIRTY seconds - that uses up 1/3rd of my open time before I've even started the pour. Surely I can skimp on the stirring a little bit to buy a few extra seconds?"

No, you can't. Why? Because you'll just end up with slushy, sticky piles of junk, like this:

...and you'll spend an hour or so trying to clean the mess out of your mold without damaging it. So do as it says in the instructions, already.

I was unsure about how much resin I needed the first time I poured it, and wound up mixing too much - it turns out I only need about 1.25 ounces to cast ten bases. The resin also expands a bit as it cures, so, it's best to "under-pour" each mold by a bit. Part of the problem is that I need to use a smaller container while pouring, to give me better control.

Here's some bases out of my first attempt:

As you can see, the details are replicated nicely. Some of these are a lost cause, though, because I poured too much resin in the mold - the bases won't sit flat.

For my second attempt, I worked a bit faster and "skimmed" the excess resin off the mold before it hardened:

This worked pretty well - it allowed me to snap off a lot of the excess resin before I even removed the bases from the mold:

And here's the results of the second casting:

All of these bases will work well, with just the usual bit of trimming & sanding around the edges.

(Update: I eventually just switched to mixing the resin in small disposable paper cups (like the "Dixie" -brand cups) - this gave me MUCH greater control while pouring the resin, and eliminated the need to "skim" the mold, or anything like that).

So, overall, it's a pretty neat process - it allows me to create a ton of custom bases, without having to build every single one of them. I need 1.25 ounces of resin to cast ten bases, and the kit includes 28 ounces of casting resin - that means I can cast two hundred and twenty-four bases with what's included with the kit. I paid $42 for the kit (after my 40% coupon), so that comes to around 18 cents per base. Seeing as resin bases usually cost anywhere from $2 - $10 from a retailer, it's a pretty good deal - Once you have the mold, you can buy just the resin for around $1 per ounce, making it even cheaper...


  1. Hey, liked the tutorial. I have all the stuff i need to do my own casting, but just havent got round to it! Thanks for the walkthrough!

  2. Thanks GunGrave - It's really not difficult at all if you take it step-by-step. I would have done it years ago if I had known how easy it was to get started!

  3. Thanks for the nice tutorial. It has inspired me to try this out.

  4. Great article mate! will be sure to give this a go at some time!

  5. Love the tutorial! Planning on following this exact process myself. So much money wasted on resin bases from Poland...

  6. Fantastic tutorial, this looks really helpful. Thanks!

  7. Amazing tutorial and one that we can all learn from!