How to Make a Silicone mold

pick your subject

With the power of silicone molding, anything can be duplicated infinitely!

Almost. There's some key things to keep in mind when selecting something to mold:

any complete Holes in the model either will require a 2-part mold (see navigation) or may be unmoldable. Try to avoid this.
Subjects with a Flat base are easiest to mold. You can get around this with a sprue, but we recommend you start with a flat-base subject.
The mold will replicate your model exactly-- so if you don't like the surface quality, fix it! Sanding is a good way to erase layer lines and surface scratches. If you want a mirror finish, you need to start with one.
The silicone will take at least 6 hours to mold, so plan to come back the next day to pick up your mold and help keep the pot open for other students. Molds will be taken out of the pot after 3 days and will not be kept for more than a week.

Making the pour container

Materials

You will need:

Cardboard for the base
Cardstock for sides (you can use any heavy paper or even foamboard)
Scissors & Boxcutter
Painter's tape (hotglue works but is more finnicky / chance of burning)
Subject model!
- Resin, 3D print
- Home object (earring, figurine, project part, anything your heart desires)

Important! for 3D PRINTED models!!

Most filament 3D prints have low infill, and there is a lot of air trapped in the prints!

This can make your print float in the Silicone and ruin the mold!!

--> to avoid this, use a Scrap of Transfer Material (from the vinyl rolls, ask a staff member for assistance) and tape it Sticky-side-UP on the bottom of your mold enclosure. This will give the model something to hold on to once you start pouring the silicone!

----> You can also glue the model directly to the cardboard base, but note that this may damage the model if not removed carefully. (If keeping the original model whole isn't an issue, don't worry!)

2. the box

Cut a base for your model out of cardboard. Rectangles are easiest. It should be large enough that the model doesn't touch any of the sides, but don't make it enormous either. You'll be filling the entire container with silicone, so avoid waste.
1. 1. It may help to trace the edges of your model onto the cardboard! Keep in mind also that what touches the cardboard will form the holes that you pour your resin into.

Measure and cut your paper to wrap around the base. Make sure it's tall enough to have a centimeter or two of height above the top of the model, as the silicone needs to wholly encase it.

Tape all seams, inside and out. We're making this ""watertight"" so silicone won't leak out. Taping the inside of the walls (right) to the cardboard makes for easier removal than taping only the outside (as if on left)
1. 1. If using a Filament print -- this is where you'd attach the transfer paper, sticky side up. (it should not be sticking to the carboard, just held on by tape)

pouring silicone

3. silicone materials

Time to make the actual mold stuff! We use a 2-part silicone that cures in ~6 hours, and has a working time of about 30 minutes. It is a 1:1 ratio by volume. (more details can be read on the containers)

You will need:

both containers of silicone (yellow and blue)
a large plastic mixing container (NOT the bendy silicone one)
stirring sticks
GLOVES (silicone is NOT a non-toxic material!)
model & enclosure

4. mixing silicone

Use the guidelines on the plastic container to pour equal amounts. There is a 1:1 ratio column that you can follow.
Be careful! the Pink and Blue have different viscosities and don't pour the same. Be mindful and try not to spill.
If you're not sure how much to make, pour a little extra. It usually takes more than you think, and extra silicone can be left in the container to cure and be recycled.
Mix with a Stirring Stick until the color is a uniform purple. Make sure to scrape the sides and bottom!

Bonus Recycling Tip! ---> for silicone pros (Not the first try!) you can dice up thicker pieces of cured silicone and pour them into the mix to recycle material. Don't use paper-thin whisps though! We've found them too unruly to be useful and difficult to clean up if spilled.

5. Reducing bubbles

You may note that a good, vigorous mixing puts a lot of bubbles into the silicone! This can be reduced by pouring carefully, but we recommend vacuuming out most of it. This will give you a much higher quality mold.

Essentially, we'll be sucking out all the air trapped inside!

Click this link for instruction on the Vacuum Chamber.

6. pouring

Once your silicone is mixed and de-bubbled, you're ready to pour!

It's important to be careful and slow during this process to ensure the best quality of the mold. Pouring long and slow will reduce trapped air, imprint better detail, and prevent bubbles that may exclude entire sections of your model.

This is especially crucial if there is any overhang in your model, such as under the chin of this squirrel.

7. curing

<<< Don't do this!!!!!!! Messy!!!!!!!

!! Before you go to cure, make a secondary base for your mold. This will catch any spilled silicone and especially resin-- which will cure to the bottom of the pressure pot and is very time consuming to scrape off. Please spare the student workers.

These are very simple to make-- cut another square of cardboard and fold a ridge of tape to stand up around the edges, making a tray for your mold.

Next, you'll leave the mold and its tray in the pressure pot to further reduce bubbles while curing. While this is technically optional, we highly recommend it for minimum bubbles and maximum detail.

to use the pressure pot, please navigate to the operation page.

and Congrats! you've made a mold!

If you want to learn to make 2-part or Capped molds, which can capture every side of detail (such as on a numbered die) or holes in a model, as well as how to make models without bases better for resin pouring (by adding a sprue), click Here.

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