Molding & Casting Tutorial: Making Master Woo

[GreyOwl]

Several people have asked me for tips on how to make molds and casts and I've been putting off making a tutorial. Well, I found the perfect excuse. I want a Master Woo but don't want to pay a lot for it. I also didn't want to sacrifice one of my monks since I only have 2 packs and want to keep both intact. So I figured I would make a mold of one and cast it, and take pictures along the way to make a tutorial.

I'll start with an overview of one and two part molds, and save the details for the three part mold, since that is what the monk requires.

Mold Types
By far the most time consuming and difficult step is making the mold. Molds can be one part (the easiest), two part (a little more difficult, but not too bad), or even more parts. It all depends on the shape and whether you'll be able to get it back out without destroying the mold. This just takes experience and some practice in visualizing things in 3-D.

One Part Molds
A one-part mold works for anything that has a flat side and can be pulled out of the mold from that side without damaging (tearing) the mold. A great example is a Heroscape base. To make that, you would first glue the base to a piece of cardboard. Use a glue you can "unglue", like Elmer's. Don't use something too strong. Then build a lego box around it, making sure you leave at least 1/4" all around, including height. Then pour the mold mixture into the box and wait for it to set. Once it's done, take apart the legos. Flip the box upside-down, remove the cardboard, and take out the base. Now you can make casts from this mold. Here is an example of this type of mold, the only difference being I used 4 different size bases in the same box:



Note that if you want the recessed details under the base instead of having it be flat, you will need a two-part mold.

Two-Part Molds
A two-part mold is needed for most things that can't be made with a one-part mold. When I made a mold of the HeroClix Magneto, it required a two-part mold. Look at the original figure:



Note that there is no side that you could use to pull out of a mold without the figure getting stuck, even assuming the figure will be de-based. The closest is the bottom, but since the feet stick out past the cape, once this is upside-down and you try to pull it up by the feet it will be stuck. Keep in mind that the mold material will fill the space between the feet so you'd have to rip that out to remove the figure, which would destroy your mold. So this figure needs a two-part mold.

Anytime you have a two or more part mold, you will have a mold line. So the first step is to determine where you want the mold line, assuming you have an option. Depending on the shape, you may be limited. With Magneto, I decided to have it run around his sided so I'd essentially have a front half and a back half.

To make the mold, build a lego box on cardboard as before and fill it half-way with clay. You must use natural clay with no sulfur in it, otherwise the mold material will bond to it. Then press the figure in half-way into the clay along the mold line you decided on. So the clay will determine the mold line. Then pour the mold mixture to fill the box. Once it sets, flip the box over and remove the clay. Spray the set mold half with a release agent (or coat it with Vaseline) so the other half won't bond to it. Then fill this half with more mold mixture. Once it is set, take it apart and you have a two-part mold. Here's the one I made for Magneto:



And here is the cast made from it:




Three-Part Molds
Some shapes, unfortunately, won't work even with a two-part mold and require more parts. A great example is if you want to make a mold of a vase. If you wanted the resulting cast to be solid, you could use a two part mold, or even a one part mold if the shape was right. But if you want the cast to be hollow just like the original, you would need three parts - 2 for each half and one to fill the inside of the vase.

It turns out that the Shaolin Monk requires a three part mold as well, mainly because of his right arm that is bent. So let's make the monk!

Making a Mold of the Shaolin Monk

Here is the original piece:



The first step is to cut him off the base. If this bothers you, then you can try to make a mold with the base still on, but I think it would require at least 4 parts. Personally, it's probably not worth the hassle at that point so if you don't want to cut the figure off the base, just buy an extra monk.



Now it's time to decide where our mold lines should be. Here are some options.

Option 1:

A two-part mold along the red mold line would result in the top half getting stuck due to the arms.

Option 2:

A two-part mold down the center line would also result in the arms getting stuck in the mold.

Option 3:

A two-part mold along the axis of the arms would solve the arm problem, but the feet would get stuck, for the same reason explained earlier with Magneto.

Option 4:

This is a three-part mold with one part solving the arm problem, and the other two solving the leg/feet problem. This is the one we need to do.

Now, build a lego box that gives at least 1/4" above and below the figure, and some extra room around the edges. We don't want it too big because it will waste mold material, but if it's too small it can tear or not give us enough room to work. Here's mine:



Now fill the box half-way with the natural clay (available at craft stores like Michael's). Push the figure into the clay so the clay lies along the first mold line - we're doing the one around the arms first. Hopefully your lego box is tall enough that the monk's feet don't reach the bottom.



Mix up the mold material. I use silicone rubber from Smooth-On (http://www.smoothon.com/). They have many kinds. I ordered the OOMOO 25 and it seems to work pretty well.



Mix it thoroughly according to the directions. Also make sure to wear latex gloves while using any of these chemicals. They're not highly toxic, but they are a pain to wash off your skin.



Pour the mixture over the figure. It's best to start in a corner and let it naturally flow to fill all the gaps.



Once it sets, 30-60 minutes later, flip over the box and remove the clay. Make sure you don't remove the figure from the silicone.



Normally, you don't take apart the lego box but I did it to show a cross-sectional view:



Next we'll do part 2 of our three-part mold. Fill half of the remaining space with clay again, being careful to pay attention to the mold line you want. When that's done, insert two small items (like Legos) into the clay. These are called "keys" and are there to make sure you can line up your mold properly later. I should have used them in the first part of the mold as well, but I forgot. It worked out anyway, though. Just be sure to insert them so they aren't symmetric, because you want it to lock in only one way.




We need to make sure the next batch of silicone doesn't bond to the existing part in the box. Left alone, it will bond and make a new solid piece. You can either buy Mold Release spray and spray all the exposed surfaces (the right way) or rub Vaseline on the exposed silicone with a q-tip (the cheap way). They both work, but you'll get better results with the spray. The texture of the Vaseline may show up in your final cast if you're not careful.

Now repeat as before - mix up some more silicone rubber, and pour it in.



Once it sets, remove the clay.



Again, don't take apart your Legos yet, but here's another cross-section so you can see the progress. Note the keys.



On to the final part of the mold. Again, use your mold release of choice to spray the exposed surfaces of silicone. This time we don't need any clay, so mix up some more silicone and pour it in.



Once it is set, take apart the Legos and you'll be left with a block of silicone rubber.



The three pieces should come apart fairly easily. If they don't, just cut through the parts that stick. This will happen if you miss a spot with your mold release. You should now have a three part mold and your unharmed (though slimy with Vaseline and bits of clay) original.



Casting
Thankfully, making the cast is MUCH easier than making the mold. For this, I use Smooth-Cast 320, also from Smooth-On. They sell plastics in all different hardnesses, but this one seems to work well for me. Mix the two parts in a plastic cup, just like you did the silicone. While the silicone was thick and took a while to set up, this stuff is a normal liquid and sets in just a few minutes.



The tricky part is how to pour it all in while keeping the mold together. There is probably a better way (actually, I know there is), but this is what I did. With the three mold parts laid out as shown above, spoon a little of the plastic mixture into all three. You'll spill excess around the edges, but don't worry about that. For the head, you will most likely get bubbles trapped in there. Work a toothpick vigorously in there until all the bubbles are gone. Wait a minute or so until the mixture starts to thicken slightly. You want it to be like honey or maybe a little less viscous. Then quickly put the two halves for the lower body together. Pour a little more of the plastic mixture down the hole if too much spilled out and work a toothpick in there to remove air bubbles. Then quickly place the top on and make sure everything is lined up. Note that you only have 5 minutes to do this from the time the two parts of the liquid plastic mixture come together.

Once the plastic is set, which takes about 10-15 minutes, take apart the mold and remove the piece. I know, it looks bad but don't worry!



All the extra plastic is the excess that spilled or got squeezed out. At this point, the plastic should be firm and solid, but still a little flexible. This is the perfect time to trim away the excess with a hobby knife. In a couple of hours, the plastic will be much harder and it will be more difficult to trim.

Once you're done with that, it should look pretty good unless something went wrong. The most common problem is air bubble. If you get bubbles in the mold, then your cast will have bumps in it. If you get bubbles during casting, then you will have hollow areas. You have to work carefully to avoid bubbles.



After this, paint it and put it on a base. There are others that are much better at painting than me, so I'll leave that up to someone else.

Feel free to ask questions if something wasn't clear!

[brickman1444]

Nice tutorial.

[Boromir_and_kermit]

Fantastic effort GreyOwl. This needs to be stickied!!!

An inspiration to us all.

Ben.

[GreyOwl]

I fixed one of the pics that wasn't working.

[Puuka]

Here is a nother similar method. The principle is the same.
http://www.toymania.com/customcorner/moldp1.shtml

The thing I noticed with yours is that there was not pour hole. Hos did you get the liquid in?

Also, "muscle vibrator" massager clamped to a table is great for getting air bubbles out. Pour the liquid, turn on the vibrator for a minute or two, and with luck, the bubbles will come up to the pour hole. Small straws like you get in bars work great for making these. Just line them up with a foot bottom or both and pour in both holes.

[GreyOwl]

The pour hole method is the better method I was referring to. If you have a pour hole, you really need a second hole for air to escape as well. Sometimes when casting very small pieces it's hard to have these as the hole has to be half the size of what you're casting sometimes. You could use smaller holes, but then it gets hard to pour into them.

Without the pour holes, you pour the liquid plastic into each half and let it partially set so it is a thick liquid. Then you put the halves together. That way it doesn't run out, but still sets as one solid piece.

The SmoothCast 320 is actually pretty bubble free because it isn't very viscous. The only time I run into problems with bubbles is if the shape traps air in one corner. Usually the toothpick method works, but if not your idea of a "muscle vibrator" works, too. It may even be necessary with other products, depending on how viscous they are.

The link you sent uses plaster of paris for the mold. It is definitely cheaper and has the advantage of being more permanent, but it won't capture fine details like silicone rubber will. It also won't flex. With the silicone, you can sometimes get by with making a one part mold when it would really need two, or two when it would need three if it is close. That's because the silicone can stretch to remove the cast. There are even rubber compound that can stretch 400% without tearing, but I haven't messed around with those too much. The choice of materials really comes down to your specific need. Most importantly, how many casts do you plan to make?

[bluejester48]

Poor LEGOs

Needs a note that says "no LEGOs were hurt during the making of this tutorial"

Anyway, great work! I however just bought another pack of the monks instead, and I have a real Woo too.

[GreyOwl]

Actually, the Legos aren't harmed. The silicone compound peels right off and then I wash the Vaseline off. Good as new.

I bought an extra pack of monks, too, but then I decided I wanted to keep the extra squad! However, I don't have a real Woo.

[Doustin]

I really have to try this. I dont have any of the Gencon exclusives, and this will be good when I want to custom one figure but not the rest it comes with. Now to find a good simple one to start with...

[skyknight]

That was pretty amazing to watch!!!! Very neat sir

[LongHeroscaper]

This is amazing! I wish I had this kind of skill.

[ron3090]

This is exactley what I've been looking for for months! Thanks!