Crafting Experiment: Milliput and Blue Stuff

For a while now, I’ve been using Oyumaru Blue Stuff (a reusable thermoplastic molding compound, if you didn’t know) to make copies of model pieces, action figure parts, and other greeblies that I think I might want to put in my bits box for later use. I’ve also kicked around the idea of using it to clone an entire miniature but I haven’t made the attempt just yet. Anyway, while my process of creating a mold using Blue Stuff remains the same (which I’ll detail below), I’ve used different modeling compounds and materials for said molds. So far, I’ve experimented with the following (all of which are self-hardening, of course) and I had the following pros/cons:

• Two-Part Apoxie Sculpt – Great at capturing details, but too hard and heavy to really use with plastic models and figures. Better for home repairs than model making. And yes, it’s called Apoxie and not Epoxy.
• Moldable craft beads – Are quick to melt in hot water and, like Blue Stuff, can be melted down and reused but dry way too quickly to be of much use in two-part molds and are not receptive to sanding (and there’s only so much you can do to get rid of excess material/mold lines with just a crafting knife). They do, however, work as a good joint-filler as seen in my custom action figure. Supposedly cosplayers use these for vampire fangs and whatnot but I would probably be leery about putting this stuff in your mouth.
• Crayola Model Magic – Bought several small packs of this at the dollar store on a whim and while it’s incredibly soft and easy to work with (not to mention it doesn't get your hands dirty), it’s a bit too soft and everything comes out a bit deformed. What’s more, it doesn’t do that great of a job at capturing details and takes a fairly long time to cure.

But one material I haven’t tried until now is Milliput, which is a two-part modeling compound comparable to the aforementioned Apoxie putty but I was told that when it cures, I has a bit more rubbery feel to it and was more akin to plastic when it dried rather than a slab of glossy rock like Apoxie Sculpt. But I'm getting ahead of myself. Now onto the process.

It begins by heating up some Blue Stuff to make the mold. The greeblies I’ve chosen for this experiment aren’t important, but I will say that they’re optional face-plates left over from a cheap SD Gundam model that I thought might make cool shoulder pads for a custom action figure. I already had a clump of Blue Stuff ready (a previous mold) so getting it back into workable shape is as easy as dropping it into some hot water. NOTE: this is a pot I use just for melting Blue Stuff and thermoplastic beads. Don’t cook food with your crafting pots, people.

After the Blue Stuff is heated up to the point of malleability, pinch off a chunk to use as the bottom mold and smush the model piece down into it. For best results, press the most detailed side of the piece into the bottom mold. Using the end of a brush or whatever you have lying around, press a few “mold guides” into the bottom mold around the piece (but space them far enough away and far enough apart so that no milliput/clay/putty gets into them in the later stages). This is required for the molds to fit together. After poking in the mold guides, pop the bottom mold into the freezer for about 5 minutes or more.

After allowing enough time to pass, take the mold (or molds if you’re doing multiple pieces at once like I am here) out of the freezer. It should be nice and firm. Don’t take the piece out of the mold just yet, because now it’s time to heat up more Blue Stuff and create the top part of the two-part mold. The clear mass in the picture is also Blue Stuff and another mold that I made previously and intend to melt back down and repurpose. I know what you’re thinking and yes, Blue Stuff doesn’t always come in blue despite the name. It’s Japanese, don’t question it. Since I have both blue and clear varieties, I like to use one color for the bottom mold and the other color for the top just because it’s slightly easier to keep track of (but it’s not a requirement).

Once the rest of the Blue (or in this case, clear) Stuff is heated up, press it down over the piece and the solidified bottom mold. Make extra sure to press it into the mold guides as well as the details of the piece itself. Then pop it back in the freezer for another 5 minutes or more.

After the top part of the mold is solidified, get ready for the tricky part: trying to get the two halves to separate. Now, people claim that you don’t need any kind of mold release when making two-part molds with Blue Stuff and while that’s certainly true (I know I never used it), I’m starting to suspect that Blue Stuff molds get harder and harder to pry apart the more you reuse the stuff. Maybe that’s just me, but I’ve seen people on youtube use petroleum jelly prior to applying the top mold and I might just try that out the next time I do this. But I didn’t do that here. I used a butter knife as a lever and was able to get between the molds and pry them apart without too much damage to the molds…or the knife…or myself. Now that the molds are separated, with the top parts laid out in a way that you don’t forget which way they fit back together, you can now remove the model pieces. Barely anything sticks to Blue Stuff once it solidifies and it also doesn’t leave any kind of goop or sticky residue. It's pretty great.

After placing the model pieces back into my bits box, I began to prep the Milliput. Unlike Apoxie Sculpt, which you need to mix the two parts for two minutes and then let it sit for five, you just need to pinch off equals parts of what you need from the two Milliput hotdogs (one dark and one light) and mix them for about five minutes until the Milliput is one uniform color. I like to roll one into a ball, then roll the other into a ball, then roll them both together into one single bar and work it around in my hands for the full five minutes, even though the colors typically blend into one around the minute and a half mark (but then again, I’ve had quite a bit of practice with mixing two-part modeling compounds so your mileage may vary). In case you couldn’t already guess, the picture on the left depicts a fully mixed ball of Milliput.

Now stuff the molds with Milliput. In this instance, due to the flat and hollow shape of the piece I’m copying, I only stuffed the bottom mold with milliput as the top mold here is juts outward and is simply meant to create that recess the original piece had along the non-detailed side. Obviously, this is going to create some flashing that will need cut and sanded off the sides but this is unavoidable no matter what you’re trying to copy. On a related note, I always like to have a spare mold of some smaller part set aside whenever I’m making one of a new piece, since I always tend to use too much putty and have some left over that I can’t bear to see go to waste. This time, I had enough excess Milliput to copy an entire 3.75” GI Joe base stand (you can never have too many of those).

After the molds are adequately stuffed, press the top and bottom together and apply some pressure, once again making sure the mold guides on the bottom line up and fit into the matching “pegs” they created when the top mold was first laid down. Some people press them together with a vice and I’ve even heard tales of crafters placing their molds underneath a dress or some other heavy piece of furniture and leaving it overnight. But that’s a bit excessive for me, since a good pinch is usually all it takes. Now the molds are ready to set aside and allow the Milliput to cure. I’d say it takes about five hours to fully cure but I tend to let it sit overnight.

Despite what the picture below might have you believe, I was pleased with the results. Yeah, the one piece came out crappy but that was more or less my screw-up in trying to snap off the excess flashing with a pair of dull snips. You’ll just have to take my word for it. What I do like, however, is the feel of the Milliput. Like others have said, its softer (a bit reminiscent of the kind of PVC plastic you see in in Figma and Revoltech figures, if I had to compare it to anything) and there’s a bit more “give” to it than Apoxie Sculpt. 

Again, this was just an experimental trial run but I can definitely see myself using this for a custom build in the very near future. Maybe not these test pieces, or hollowish and/or flat pieces in general (as this attempt and numerous others have taught me, they’re just not worth the effort in copying) but I’m still glad I gave Milliput a shot. It's super easy to work with and it's a hell of a lot less messy than Apoxie Sculpt.

I’ll probably try Army Painter brand Green Stuff modeling clay next, but for now, I’m satisfied with Milliput. It’s in the same $10-11 price range as Green Stuff and you seem to get more Milluput for your money, though it largely depends on the different quantities of Milliput you want to buy (like most things, I just went for the most inexpensive box of the stuff I could find on Amazon).