Silicone Mold & Model Prep:
Step1: Develop a plan
The reason I list this as a step is because I didn’t have one when I first tried to commando mold and I felt like I was flying by the seat of my pants the whole time. With that said, you will want to get a good idea of how you will do the subsequent steps in this tutorial (Ex. Mold Keys) before starting the process. I personally like to draw a design for mold key placement before I start so I know where they are going to go before I get to that step.
Step 2: Model Prep
When creating a mold, it’s important to first prep your model before you begin laying down the silicone.
-Add a base to the Helmet
-Fill in holes that can potential trap silicone molding material in the wrong area. Pay attention to detail areas & the visor. I put a layer of clay between the visor and the helmet shell to prevent the silicone from dripping into the inside of the helmet and connecting with any silicone at the bottom of the neck opening. You will also want to create a seal around the neck opening and the base the helmet is secured to (my base was made from cardboard & I used clay to seal it up).
-Spray down the helmet with a light coat of release agent before you begin step 3 (I used ease release for this and waited 15 to 20 mins before moving on)
Step 3: Silicone Print Layers & Keys
When I did the print layer for the Pilot I decide to use two layers of un-thickened silicone (No Thivex) to capture the detail better.
Layer 1 (Detail covering & Registration Key Creation)
This step is one of the most important layers. The basic idea is to get the helmets detail fully covered (possibly the whole helmet, but more importantly, the detail) and create the registration keys you will use in step 4.
Registration Keys: Created by taking a paper roll and hot gluing it to a base, or using solo cups. I used a wooden base and some left over cardboard roll to create the smaller keys and solo cups for my larger keys. Now let these setup (these will be used in step 4)
1st Print Layer: You are going to want to apply the silicone in a jabbing motion into the fine details to minimize air bubbles within the print layer (ex. carved in detail lines). Once your details are covered, brush on the remaining silicone over the helmet, hopefully you have enough to go over the whole model (If not don’t worry-see layer 2).
Layer 2
Now that the silicone has cured up enough to apply a second un-thickened layer, mix up another batch of your two part silicone rubber and start on the second layer fully covering any areas you may have missed in the first layer and fully covering the model one more time. You will know it’s ready because the silicone will no longer stick like super glue to your gloves (it will still be tacky, just not real sticky). Test the spilled silicone at the base of the model. (Not the model itself) so that you don’t disturb the silicone on the actual model (you don’t want to pull partly cured silicone from the model and trap air between the 1st layer and the surface of the model). Once you have completely covered the model and the dripping silicone has subsided, you can let the 2nd layer cure up. But first, take the cheese cloth you cut up in the beginning and lay it down the back of the model long ways. This cheese cloth help add in some security against the mold wanting to tear all the way to the front (Thanks Smooth-On for the advise).
De-molding the registration keys for Step 4. Check to see if your keys from your previous step are cured up before moving on to step 4. They should be firm enough to start de-molding from the solo cups & cardboard roll or ice cube trays. You will want to take them out of their forms and ready them for the first layer of thickened silicone in the next step.
Step 4 Thickened Layers (2X)
Layer 1: Now that the first two layers of un-thickened silicone are cured enough to begin the thickened 3rd & 4th layers, it is time to break out the thivex. I generally eyeball it. Keep this in mind, the more you add, the thicker it becomes (you will get the hang of it, if you’re breaking your mixing sticks, you may be using too much, or your mixing stick isn’t strong enough). Once the fully mixed & thickened silicone is ready, use your Bondo spreader to spread the rubber all over the helmet. You want to fill in any undercuts and create a nice even layer all around.
Applying the registration keys: Once the thickened 1st layer has been applied but before cured, start sticking your keys all over the mold (be sure to refer to your mold plan, your molding plan should have already outlined where you want your keys to go). Now let the silicone cure up enough for the final thickened layer of silicone.
(I actually cut the top 2 large keys in half later and used them in different areas, 1 up front on the chin and the other I cut in half and placed them over the vents)
Layer 2: Now that it’s time to apply the last thickened layer, you will want to mix a batch up again of thickened silicone. Once mixed apply and smooth out the surface of the silicone mold nice an even. Be mindful of any areas on the keys that may get caught in the jacket of the mold and try and cover & smooth those areas around the keys that could potentially create problems with the silicone seating properly with the Jacket/mother mold portion of the mold (Jacket has not been created at this point). Use some of the silicone rubber to create a sort of Mohawk style key down the back of the helmet area. It should be place right over the area you used the cheese cloth on. This Mohawk will help the silicone portion seat better with the jacket and create strength down the parting line of the finished silicone mold.
Step 5:
Once your last layer of thickened silicone has cured past the point of being tacky, you will want to flip the whole thing upside down. The silicone needs to be cured enough not to get damaged at this step. Now, mix up some un-thickened silicone and pour it around the base. Use a brush to get all the silicone to collect around the helmet filling any areas you may have missed during the previous steps. Let this cure up and cut any dangling pieces of cured silicone off the mold. Flip back over once this has cured up firmly enough not to flow and the silicone portion of the mold should be complete.
Quality assurance test. Give the mold a look over and see if there are any issues or thin areas, you may not need to do anything, but it’s a good Idea to check and see if you have any additional thin spots that may need to be thickened up. If not, proceed to the next step. If you do, then tend to those areas at this point and then proceed to the next step once the additional silicone has fully cured.
