Captain Dunsel's Mego Madhouse

The thicker your plastic is poured, the quicker it will harden. For Mego-sized head casts, allow about 5 minutes for the plastic to cure completely. Then, remove your mold from the containtment cup.

PLASTIC CASTING TUTORIAL

Creating duplicates of an original or custom piece from a rubber mold

STEP 2: POUR YOUR CAST

Now you're ready to mix the liquid plastic compound to pour into your mold! Before you continue, note that Smooth-On's SmoothCast 300 liquid plastic compound Part A (Yellow Label) contains methyl diphenyl diisocyanate which, among other things, can cause severe skin irritation. Cured to its solid state, the plastic is safe to handle, but I strongly recommend wearing latex or vinly disposable gloves while handling the plastic in its liquid form.

Playing with Plastic... (prerequisite: MOLD-MAKING TUTORIAL)
Now that you have a mold of your object, you can easily reproduce the object using a liquid plastic/resin compound. As stated in the Mold-making Tutorial, the process below is shown using products from Smooth-On. Their products are available individually, or for first-timers, in an all-inclusive sampler kit.
Go to http://www.smooth-on.com. Click on ORDER ONLINE, go to GETTING STARTED and get the $25 POURABLE URETHANE SUPERSAMPLER. This starter kit contains everything you'll need to make molds & cast resin plastic parts:
     - Evergreen 20 liquid mold-making rubber
     - Smooth-Cast 300 liquid plastic compound for casting
     - Universal Mold Release - very important stuff!
     - SuperSeal sealer
     - "How to Make Molds & Castings" booklet

Ingredients...
Here is a list of items you will need to make castings:
     1.) Your mold and it's containment cup (see MOLD-MAKING TUTORIAL)
     2.) Universal Mold Release
     3.) Small plastic funnel (optional - read ahead)
     4.) 7-ounce transparent plastic cups (x2-3)
     5.) A toothpick or chopstick
     6.) Smooth-Cast 300 Liquid plastic compound (Parts A & B)
     7.) A plastic disposable fork

Ready to Go!
The following 3-step instructions will take you step-by-step through the plastic casting process using a premade mold discussed in the MOLD-MAKING TUTORIAL):

PLASTIC CASTING TUTORIAL

STEP 1: PREPARE YOUR MOLD
Coat the inside of your mold with universal mold release before each casting. This is important to ensure clean removal of casts. Without the mold release, the plastic cast will bond to your mold and demolding the cast will destroy the mold itself.

LIke the mold rubber, the two-part liquid plastic is a 1 to 1 mix ratio, so pour equal amounts of parts A & B into each of the two cups. Pour enough of each so that, when combined and poured into the mold, the total amount will completely fill the mold cavity.

Take your time to measure carefully--compare the cups side-by-side.

When you have measured equal parts, mix parts A & B together in one cup.

Using a plastic fork, stir for briefly (10 seconds or less). Smooth-Cast 300 has a pot life of only 3 minutes, so don't spend too long stirring--you'll need the time for pouring!

Finally, pour the mixed liquid plastic into the mold. To reduce the occurrence of bubbles, pour the plastic VERY SLOWLY in a THIN stream. The liquid plastic will get warm as it begins to chemically harden -- If you feel this happening don't worry, you still have a little time before it hardens so don't rush the pouring.

STEP 3: DEMOLD YOUR PLASTIC PIECE

Peel off and discard any extra overpoured plastic. This extra plastic is called "flash".

Now you have a finished plastic resin cast -- an exact positive permanent duplicate of your original part -- ready to be sanded, drilled, painted, etc.!

With a steady hand, you can pour directly from the bottle into the mold's pour hole--but this is where I recommend using a small funnel. In these photos, I use a soft plastic cup as a "go-between" in place of the funnel.

As before, when applying the universal release agent, DO NOT use the spray pump that comes with it, as the spray is very ineffective and wasteful. Instead, complete coverage is achieved best by pouring an amount of mold relase directly into your mold through its "pour hole" (created by the wooden dowel in the mold-making tutorial).

Cover the pour hole with your finger and rotate the mold in all directions, making sure the mold release inside gets into all the crevices and detail of your mold.

When finished, pour the excess release agent back into the bottle and replace its cap. Again, this is shown using a cup, but you may use a funnel or pour directly from mold to bottle.
Also, make sure that some of the excess mold release coats the top of your mold--the part surrounding the pour hole.

* Now, allow a minute or two for the release agent inside your mold to dry, then move on to STEP 2. *

Replace the mold into its containment cup. Use a new one if you cut the original containment cup while demolding your prototype piece.
(STEP 5, mold-making tutorial)

If the cup does not hold the mold snug...

...use a toothipick or chopstick as a wedge to seal the slit part of the mold together.

...follow the "Shake Well" instructions on the liquid plastic bottle(s).

SAFETY FIRST!!!
Mold-making & casting can be a fun hobby, but remember that you are working with chemicals. Please take the time to read all MSDS (Material Safety Data Sheet) information provided
and take all possible safety precautions.

Grab two more plastic cups identical to your containment cup and...

While "shaking well", you might want to cover the bottle lids with scrap cloth or paper towels to prevent any accidental spilling or leaking.

Fill the mold completely to the top of it's pour hole. If you wish, you can give the mold a gentle squeeze to push out any possible trapped air bubbles, but this is generally not necessary.