Silicon molding and resin casting, from scratch.

[kiki-chan78]

Okay, taking a second stab at this since last time my thread kinda got 'hijacked' by my kitten. ^.~

Instead we're gonna go from the beginning and making the *boxes* for the silicon molds. I've got four pieces that need pressure molding. They will all end up with two part silicon molds. The difference between non-pressurized mold making, and pressurized mold making is that while you can make a non-pressurized resin cast in a pressurized mold, you can't really go the other way since the resulting piece would be rather on the 'spikey' side.

For this, you'll need:

-Piece to be cast.
-Foamboard
-White glue
-Scotch Tape (optional)
-Ducktape (make sure it's good quality, the cheap stuff is just that... cheap and not really worth the hassle)
-Ruler (preferably metal)
-Calipers (optional, but quite handy)
-Exacto knife (be careful when handling sharp instruments)
-Non-oil based clay or Super Sculpy (the silicon will suck the moisture out of the Super Sculpy eventually rendering it useless)
-Silicon
-Resin
-Kitchen scale
-Cup to mix silicon in
-Stirrers (I use the paint-stirrers that are handed out in Home Depot)
-Vaseline or Silicon mold release (if using vaseline, also have a small-medium paint brush to apply vaseline)

If you are planning on casting under pressure:

-Compressor
-2gallon pressure pot

The silicon and resin that I get is from Sterling Supply. I use GI-1000 silicon, and white Alumilite resin. Normally I'll pick up a gallon or two of silicon at a time, with an extra bottle of activator as well. One gallon is about $100, and a two gallon kit of resin is about $115.

FYI, it took more than two full molding sessions to get the final version of Allison, and each round of molding took about two gallons of silicon.





Here's the four pieces. Alice and Aaron human heads, Alice waist, and Alice ribs. Throughout this, I'll be concentrating on the Alice Human head's mold, even though I'll also be making the molds for the other three in tandem.

Before anyone says anything, no, those are not grey resin and I currently have no plans on producing grey dolls as of this time. The grey color is a primer that makes imperfections easier to view on surface. ^.~






First thing that you need to do is take measurements. I've got a set of calipers which are completely indispensable for my mold-making endeavors. FYI, Zirc's husband will trace around the piece and get his measurements like that; so that's something you may want to try if you don't have a set of calipers on-hand.

You want width, height, and depth. Round up to the nearest quarter inch, never down.



This is the time that you want to think about what orientation you want you piece to be cast in. The Alice head will be cast face-down to ensure the least amount of trouble with getting the face to come out with the least amount of flaws. Air rises, so you want the part on your piece that you care about the *most* to be faced down. In Alice's case, it's most obviously her face that I care out since I can always sand problems off the back of her head.

Her pour spout will end up attached to the back, hence the reason for the additional quarter inch on the depth. ^.~

Now that you have Height, Width, and Depth this is time to get the rest of the measurement to make the box. Foamboard has a thickness of a quarter of an inch. Just replace x, y, and z in this image for h, w, and d. X variable corresponds to the pour spout, in the case of Alice's human head, X equals D.



Also got the measurements for all the other parts as well. Turns out that Aaron's dimensions follow Alice's to the point I didn't bother with finishing his measurements and just used grabbed Alice's. Drawing this out as you go is quite helpful.







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Now that we've got the measurements, it's time to cut out the parts of the box.

Cut out two of each measurement set from your foamboard:

- AxB
- AxC
- BxD

Always check and re-check measurements to be on the safe-side. If you are doing several boxes in tandem, it's a good idea to find the largest common measurement among them all to be most efficient.

It is also useful to have a self-healing cutting mat for this step. Otherwise, cutting carefully with several newspapers stacked underneath is also an option. Either way, take care since you will be handling sharp objects.







I make sure to use metal rulers for cutting, since if you are not careful the exacto blade can accidentally catch on a plastic ruler.

For a clean edge on the foamboard, it is always best to have a new/sharp blade. Dull blades can cause problems with the foam and start to tear it.

Keep all parts and pieces together. This makes it more convenient and easier to keep track of what is being done. It also helps a LOT to label what measurements each part has once it's cut. If they get put to the side, this way you will know where they go.

Here is the pieces for all my boxes with their respective parts.







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Now to assemble the box. This is pretty straightforward.



White glue is used to temporarily hold the sides together, with scotch tape providing more support.







Once the box itself is together, the ducktape is used. Long story short, this thing is being made as 'water-tight' as possible. Ducktape is only a couple of bucks a roll and silicon is expensive. When in doubt, put more ducktape.

I've a pretty specific application format that I stick to when putting the tape on. This is making sure that there are no crevices that the silicon can slip out of. It should also be noted that I tend to primarily use the pink tape, mainly because it's pretty. ^.~









Yes, this kind of 'mummification' is done to all my mold-boxes. As stated before, the tape is cheap and silicon is expensive. It only takes one box to fail to ensure that you reinforce *all* of them.




To finalize this section, here's a shot of all four parts with their boxes.







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Gonna pause here for the time being... mainly because I'm about to collapse. ^.~

[EAB]

I can see why. I need a nap just reading this.
Flawless pieces, though, so worth every bit of the work.

[zirconmermaid]

She should tell you about the time the cheap duct tape failed - messy! Just FYI, Alumilite Resin is identical in appearance to BBB/RS white as far as I can tell comparing them. Gerald and I use a different resin, and it tends to look just like Dollzone white.

[kiki-chan78]

That was HORRIBLE when the tape failed on me! The ones that failed were Allison's shins, both of them. This was on the second half of the molding process, and proceeded to drop about 4 cups of silicon into my pressure pot. I lost the molds, and had to re-do everything on them from scratch! I cried.

Basically, $25 worth of silicon was lost because I didn't spend an extra buck on tape. -_-;;;

[kiki-chan78]

Okay, so here's more silicon mold-making. ^.~

Now that we've got our boxes ready, it's time to 'crack' them open.







Think about where you want the seam on the part. Since this one is the head, the seam will go around the top. Keeping in mind that we need to keep a quarter of an inch allowance around the piece for the silicon mold, and that the foamboard is a quarter of an inch thick, measure down half an inch and cut the box into two parts.







I'm not going to pour the silicon down into the mold box with the face oriented down, because that might allow air bubbles to get caught in the eyes, nose and ears as the air rises. Instead, I'm cutting a 'window' into the side to pour the silicon in.







Now start filling out with clay the area of the mold that you *don't* want the silicon to flow into. Be mindful of how your mold will fit together when finished. You don't want any sections that will be too problematic to take the piece out of, since that will give the same problems for each casting. Also. the less 'undercuts' there are, the less stress the mold will endure and the longer it will give good resin casts.

The little divots and lines deliberately sculpted into the clay act as 'keys'. When the silicon mold is finished, these parts will slide together and essentially 'lock' together so the silicon doesn't slip and accidentally ruin the resin cast.









Once you've got the clay in place, seal that puppy back up with more ducktape.







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Now let's have a look at the molding of the ribs. They are a relatively unique shape, and gets an interesting mold layout. I don't have enough clay to finish 'filling' out all four of the molds, same for silicon... though, I've got two more gallons on order which should arrive in a couple of weeks. *squee*

Anyway, here's the ribs. These are for what's known as a 'master-mold', a final mold to make parts for Alice. The above head will be molded one more time before she's finalized. ^.~







This piece will have it's seam down the side of the ribs. Which means that instead of cutting off only one side of the box, this box will be cut down the middle. The silicon will be poured in from the top, so that's cut out first and then the entire thing get's halved.









As with the head, the ribs are filled out with clay. Again, keep in mind how the mold will be pulled apart and place 'keys' accordingly.









Since I'm a dork, I didn't get a photo of this mold put back together. -_-;;;

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Now is time to get out the silicon.

I use the GI-1000 silicon. The 'kit' that is in these photos is the gallon kit.

Weight out the silicon, and add activator equal to 10% of the silicon weight. More activator that's added, the quicker the silicon sets up. Silicon likes heat and humidity, which is kind of the opposite of resin. With the activator in the silicon, mix it up so that it's all one consistent color.











Once the silicon is one solid color, pour it into the mold. Try and keep a thin stream going in. Using a thin stream will help reduce the number of airbubbles that get into the mold. The less of those in there, the better the mold will turn out.







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Please try to use hearing protection when working with compressors since they are loud!

Turn on the air compressor. You want about 40-50psi. By keeping the pressure adjusted on this side, you make sure that too much pressure can't accidentally be pumped into the pressure pot.







Stick mold into the pressure pot, clamp it shut, hook up the hose and let sit over night.

[Dirili]

So great that you are doing this! I've read lots of tutorials and not sure if I'll ever make a doll myself, but it's still fascinating And the more detailed, the better.

[Rosinha]

What Dirili says. I"m interested in doll-making, but not experienced even in handling dolls. This is so insightful. Thank you so much for showing this!

[EAB]

I am flabbergasted. I could never do this in a million years, but it's fascinating. Thank you for doing this.

[kiki-chan78]

Resin casting isn't for everyone. What's worse is that after extensive use, silicon molds will wear out and must be replaced. By 'extensive' use, it means that after about 20 castings (30 if you're REALLY lucky and have absolutely NO undercuts) the mold has degraded to the point that the parts cast start coming out badly.

This process gets done for each single part of the doll, and each and every single time the molds wear out. Yikes!

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Pulled the molds from the pressure pot. Not sure what's up with the Alice one, got a set of funky looking bubbles on that one. Can't tell if that will cause problems when casting, and won't be able to see and potential issues till after pouring the second half. ^.^;;;







Open the molds up and carefully pull the clay out. Now take the vaseline and brush a thin layer over the silicon. This will make sure that the new layer of silicon won't attach itself to the old. Silicon LOVES sticking to silicon.







Ducktape the boxes shut again. The ribs are going to be filled through the side, since I have to get the silicon up inside the piece and over on top. I closed up the top of the mold with more foamboard duck-taped into place. This way I don't have to worry about silicon pouring out the top of the box.







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Right now I'm scraping the bottom of the silicon bucket. Once my silicon order arrives, I'll resume posting updates in this thread. ^.~

[Nella]

This is such a fascinating process to learn about.