Molding and Casting Tutorial or the Blind Leading the Blind

Step 1: Turn back now while you still can! Okay? Seriously...


























Still here? Wow, alright then. Keep in mind I'm not entirely sure what I'm doing either but this is what I have learned so far through trial and error.

Step Two: PLANNING, sure it sounds like a good idea now but the reality is probably more insane than you anticipated.

You're going to need:

1. Mat/table covering/cheap cutting board - something to keep all the chemicals from spilling onto your workspace.
   
2. Plastic/rubber gloves - don't let this stuff touch your skin.
3. Ventilated area/hazmat suit - don't breathe this stuff.
   
4. Disposable strong stirrers - I use tongue depressors.
   
5. Dixie/paper/see-through plastic cups - for mixing.
   
6. Small measuring cups - try to find something disposable or something that will be dedicated to this process forever.
   
7. Plasticard - go to a hardware store and get some 'For Sale' signs, see below.
8. Clay/stopgap material.
9. Rulers and pens - for measuring.
   
10. Your custom model, mold and casting mixtures.
11. A plan - what the hell are you really trying to accomplish? Why are you making multiples of this thing? Do you REALLY need to make multiples of this thing?
    

So let's start with something simple aka something I actually made that didn't end in disaster: custom bases.


So you made some custom bases and you'd like to make them over and over again consistently say, for your whole army or whatever.

Step three: planning the mold. This is a lot more difficult than I originally thought it would be.

A mold needs:

• to be a stable piece that allows you to pour a casted material into it without spilling or creating unnecessary mold lines or flak lines on the model.
  
• to allow easy access to the casted piece. If it is a pain in the ass to get the original piece out you can guarantee the casted piece will have the same problem.

I found that drawing out a design works best.

Step four: a box for the mold. Since you are pouring liquid around the model you'll need to be able to contain it. You need a box to contain the model and it needs to be the right dimensions so go buy yourself a ruler and a protractor, maybe even one of those fancy rulers that has a built-in right angle so you can accurately make corners.

For materials I would NOT use cardboard! The mold material sticks to it. I would use plasticard and I would buy it from a hardware store: these are perfect!
Cheap, lots of it!

Measure the dimensions of your model (the bases in this case) and then build a box to contain them. Keep in mind that you're going to want the box to be deeper (or taller, etc) so that when you pour the mold mix over it the mix will cover the model completely!

Now that you've got a solid container, make sure the edges are filled or it will make a huge mess.
But what's this!
That's going to drain straight onto something so fill it with something:
Clay works well and generally can be re-used. Coincidentally this was originally the material I was going to use to sculpt with.

Now that the box is secure arrange your models so that they don't touch each other or the walls. You can secure them to the box with clay or a little glue.

Now that everything is ready we can look at the mold material.

Step Five: the mold.
Meet Oomoo: (the website and the instructions I received say two different things) a two part, 1:1 ratio mix by volume, no heat or vacuum sealing required mold compound from Smooth-On. I recommend starting with the $25 trial size as it will last you for your first baby steps towards bigger things.

Words of caution:

• this stuff is sticky, lay out some sort of cutting board or some sort of mat you can throw away later and wear GLOVES
• VENTILATION, these are chemicals which are not friends with your lungs, eyes, and other vulnerable tissues
  
• Part B is a blue substance that pours like thin syrup (slower than water at any rate)
• Part A is a pink substance that comes out in GLOBS and has the consistence of molasses
• the bottle do not lend well to pouring and tend to drip hence I started keeping them in plastic bags because the unmixed substance does not clean off easily.
  

Start off by taking the measurements of your box (height x length x depth) to get your volume estimation. Of course, if you're any sort of scientist you'll just measure in metric and realize 1 cm^3 = 1 mL and it's an easy day. Otherwise you can convert your measurements via Google if need be. You could try to determine the volume by merely pouring water into your box and then measuring the amount of water with the model in it. I wouldn't recommend this tactic... Unless your model is huge I wouldn't bother with this because you'll need a little extra anyways to cover your model entirely. Better to have more than you need vs. not enough!

Now take that number and halve it (one half will be part A the other B). Measure out equal potions of each. Being a little off isn't going to ruin anything as far as I can tell so far...

I haven't found a good measuring tool. This stuff is opaque, is a pain in the ass to clean, and generally clings to any surface it touches. Right now I wrap a metal measuring tool in plastic. This is not ideal but it has worked so far.

Those little cough syrup things might work too.
Now dump both into a cup:
As you can see here I used one of those disposable paper cups. I actually recommend see-through plastic cups so you can see if you've scraped the edges off enough. I haven't used them myself but the paper has worked so far now.

You've got 75 minutes before this stuff solidifies (cures) so take your time.

Stir it up. I got some tongue depressors because this is a thick mixture and lesser stirring utensils might snap. Stir until it is a solid purple and make sure to scrape the edges and the bottom to get it all together.

Place the box on a level surface and then pour the mold mix into one spot in a steady slow flow and let it fill.
Use the stirrer to scrape it all out until the top of the model is submerged and has a little substance above it. If you didn't mix enough the top of the model will show through and you'll have a hole. If you're quick you can mix some more and cover it... This may have happened to me because I didn't plan ahead.

Now set a timer and go do something else for 75 minutes or more, if you're so inclined.


Welcome back!

Step Six: recover (hopefully) the original model and mold. With the bases this is rather straight-forward: take the entire mold out of the box (this might require you to destroy said box) and flip it over. Since you had the bases face-down that is what you should be seeing: the bases facing up at you with their tops inside the mold. Pop them out and see if anything has gone amiss:
If you look closely at the top row 1st and 3rd from the left bases you can see that there is mold material stuck inside the original model. The irregular arrangement of edges or your careless hands have cause bits of the mold to break off into the model. As of yet this can not be repaired as far as I can tell. The skull base (2nd row, 2nd from the left) also has some of the mold in it.

Additionally there may be some edging or lines that aren't supposed to be there on the mold. You can clean these off this a knife but BE CAREFUL. One wrong deep cut will pierce right through the mold.

Also any problem you have getting the originals out will also happen with casting. For example I tried to make some custom skeleton parts and then cutting the mold in half to retrieve them. I was too hasty and this is the result:
Now if I try to cast it the pieces not only come out irregularly but they are a pain in the ass to get out. Keep this in mind when you plan your mold as retrieval is crucial and may make the mold effectively worthless.

Step Seven: casting!
Meet Smooth-Cast 300 white liquid plastic. 1:1 mix by volume, no vacuum sealing (degassing), etc.

Words of caution:

• Part A and B are clear mixtures.
• These things pour FASTER than water. This was a nasty frakking surprise after the mold mix.
• You've got 10 MINUTES to pour this stuff after you mix it.
  
• Curing is a EXOTHERMIC reaction! It gets really hot!
• The container you use to mix this and the stirring rod will be covered and unless you intend to re-use them for this exact process, will be coated in solid hard plastic.

Preparation for this one is tricky because you're measuring the volume of the model itself. Remember the water technique I mentioned for measuring out the volume for the mold mix? That's the only way I've discovered to measure it all out without ending up with a lot of extra material.

So measure, mix, pour with a steady hand. Pour too quickly and bubbles will form or you'll overfill the mold. Pour at the lowest point of the model and let it fill to the top. You can take your mold and sort of pick it up a little and drop it down to slam some of the bubbles out, be careful though.

Wait 10 minutes (you can actually see it change from clear to solid white and it heats up, NEAT).

Take out the casted piece just like you did with the originals:
Did it work? Are there any mold lines? Did some of the mold break off into the piece? Mine did so now the next casted piece will show that deficit.

Try it again and again:
Here you've got my small bases, medium, and beetle.

Step Eight: practice. You get better over time, naturally.

Here are some resources:

Smooth-On: one of the more friendly websites for this process and one of the few that isn't so brutally technical that you can't understand it. I buy everything here for now. There are LOTS of things you can do with their products and some neat tutorials. Be sure to read up on whatever you buy first or you'll end up with products you can't use properly!

They actually have a product called Sorta Clear that acts as a semitransparent mold mix so you can cut into it and SEE what you are doing rather than cutting a mold blindly. Problem? It requires to be degassed. Degassing vacuum chambers are stupid expensive (like $500 for the pump alone) so I wouldn't bother unless you get really serious about this process or you find something cheaper.

Hirst Arts: makes scenery molds and has some good tutorials as well as BRILLIANT things to make into REALLY customizable scenery.

Sersi's DakkaDakka custom army thread: details this cool cat Sersi's production of some FINE sculpts followed by making custom molds. I haven't entirely figured out how to duplicate the process but it is one of the better pictured productions that I've seen.

Well that's that. I'm trying to sculpt some models right now with the intention to mold them. I'll let you know how it all turns out!