When Julia and I want to take a break from writing our theses, we both agree that pouring silicone into 3D-printed molds (see our other tip about those) is one of the most satisfying and oddly calming activities at Ontario Tech University. Other than its therapeutic effects on a couple of health sciences graduate students, it serves as a great way to create simulators for teaching clinical skills. We’ve been experimenting with silicone quite a bit in our lab, and so we’d like to share with the simulation community what we’ve picked up along the way thus far.
Silicone and Other Products
There are many kinds of silicones out there, but at our lab, we have been sticking to Ecoflex and Dragon Skin, two kinds of silicone made by Smooth-On Inc that are versatile and easy to use. We prefer these two in particular because they can be cured at room temperature with almost no shrinkage. The resulting rubber is soft, very strong, and can be stretched many times its original size without tearing, making it perfect to replicate skin and anatomical models.
There are additional products we sometimes add into the silicone to achieve certain effects. The most common are the four Ds:
Droopy, not a problem: To get the silicone to stick to vertical surfaces in molds, we use THI-VEX to thicken the silicone.
Deeper layers: For a softer and flesh-like feel to the rubber, we mix in Slacker which changes the tackiness of the silicone.
Details, details, details: For molds that have very minute details like wrinkles, we like to spray Ease Release on the mold directly before casting so that all of the rubber, especially when it gets into the small spaces of the mold, can be released easily.
Diversity: Lastly, to add colour effects to our silicone models, we tend to use Silc Pig pigments from Sculpture Supply Canada. These are excellent because a small amount for a proportionally large amount of silicone goes a long way! For all of these items, be sure to read the label on the product for the suggested amounts for the best outcome.
Before you begin to use silicone, equal amounts of Parts A and B need to be mixed in a container to generate the chemical reaction that will begin the curing process. We like to use a scale to ensure equal parts, but if the measurement is off by a few grams it’s not a problem. The mixing needs to take place for about 3 minutes while scraping the sides of the container so that both parts and pigment are well combined. Finally, alcohol wipes have become our best friend when it comes to accidental spills, they make cleaning up dried silicone easy.
We hope that you find these tips and tricks helpful if you plan on using silicone for your simulation projects. Let us know what you think about these and we’d be happy to hear about your experience using silicone! Have fun pouring silicone and make sure to wear some gloves and a lab coat!