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Carbon’s Cosplay Corner: Resin Casting, Part I – Making a Mold

Hey y'all! This month, I had originally planned to talk about magnets, but I did my first few resin casts and it was super fun & easy, so I've decided to talk about that! Don't worry, we'll still talk about magnets, it'll just be about 2 months later than planned.

First things first when talking about working with any sort of chemicals and that's safety! Depending on the products you use, you'll have to follow different safety instructions, so be sure to read ALL of the information both on the inside and outside of the packaging. I've been using smooth-on products for about 4 years now, so I purchased their 2-in-1 mold & casting kit because I would be able to use some of their dyes that I've purchased before. You can purchase it in two parts on amazon (mold & resin), or on their website.

Materials

  • Mold kit
  • many disposable mixers
  • 3+ large disposable plastic containers
  • 2+ small disposable plastic containers
  • tin foil
  • paper towels
  • gloves
  • protected work space
  • 1 old box per mold
  • hot glue
  • object to cast
  • permanent markers (optional)

Materials needed to make a mold.

Before we start with actually casting, we need to have a safe work space. One that will not only protect you, but also one that will protect the environment you're working in. My personal setup is a little bit of a mess, but it includes 3 layers when I'm doing resin work. The first layer is going to be a blue tarp that I purchased from Harbor Freight for about $5 (you can see it in the background). Mine is very large, but you can use a smaller one if your space is more restricted. You can also find them for sale on Amazon and at Walmart, Home Depot or Lowes. On top of the tarp, I have a pack of these EVA foam mats that have been damaged at some point. As you can see, mine are now covered in remnants of paint, resin, modeling past and scars from where I've cut into the foam. This layer will protect your floor or table from any accidental (and permanent) damage. The final third layer is an optional layer of tin foil. This will help keep clean up quick and will ensure that you don't get any unmixed or uncured materials on you or your props.

Making the mold

Now that you have a prepared work space, it's time to start making your first mold! First, you'll need to make a disposable box to form the outside of the mold. I normally use old tissue or cereal boxes, but you can use anything you have in your recycle bin. Start by measuring about 2cm higher than the object you're casting and cut the box in half so that you're left with a cardboard bowl.

  

Now you want to go in and seal all of the edges that might be open with hot glue. The bottom of my box was very well sealed, so I skipped this step. Be generous with the amount of glue you use, because it will make sure that none of your mold seeps out of the box! You might want to use some of the remaining part of the box to make the inner space even smaller so that you waste less silicone. Below is a picture of a mold box that I made for a small cast. It isn't very glamorous, but it gets the job done. Notice the inner support blocks off some of the inner space and makes the mold smaller. I also cut off the outer edge of the box, because I didn't need it and it was getting in the way of my hot glue gun.

Now that you have your mold box made, pull out the instructions from your mold maker and start reading! Each mold uses a different combination of chemical reactions, so it's very important that you understand what your mold kit needs. If you're using the kit I linked to above, there's a very handy instruction sheet. Start by priming your mold and what you're casting. This is similar to buttering a baking pan and will ensure that your mold will easily separate from the mold box. I decided to prime these two separately because of all of the small curves on Cyndaquil. Once both are primed and dried, I hot glued Cyndaquil to the bottom of the mold. The hot glue doesn't need to be hot, it's just to tack him in place.

To mix the mold , you'll need 3 large containers. One for part A, for part B, and for mixing. I normally use old (clean) plastic take out containers. If you're using a silicone mold, it will peel right out of the plastic mixing container, so you can use it over and over again. Ideally, you want to use a scale to measure out all 2 part Smooth-on products, but I've found that it isn't always necessary. If you use clear containers, you can simply place them side by side, or you can purchase a cheap set of measuring cups if your A:B ratio isn't 1:1.

Finally, just pour A & B into your mixing container and stir! Pouring viscous materials can be very difficult, so I normally use scrap EVA foam as disposable scrapers and mixers. While mixing, be sure to stir until there are no swirl lines and scrape the edges of your mixing container with your mixer many times. For awhile it's going to look like those crazy yogurts from when you were a kid, just keep mixing until it's all one color. Once it's all mixed up, just pour it straight into the mold. If your mold has a lot of holes or divots, be sure to pour very slowly so that all air bubbles can escape. Once the mold is all filled up, tap the container on the table a few times to help shake out the rest of the air bubbles. You can also gently flick the side of the mold box.

Once your mold is cured, you'll need to separate it from the mold box. For this, you can generally just rip the mold box apart. If you can't tear it with your hands, you can also cut it out with a box cutter. If you use a box cutter, be very careful to not cut too far into the mold. You only want to take the box apart, not the mold itself. You might also need to trim part of your mold. If the hot glue didn't cover the entire base of your object, you'll have a small lip of silicone that covers the hole. If this happens, you can carefully trim the lip off with a box cutter. Then just pull out your object and you're ready to start casting! In the two images below, you can see that the base appears to be smaller when it's inside the mold, this is because the lip is covering up the edges.

  

Key points

  • Fully read instructions before starting
  • Glue down the part you're casting
  • Triple check that the mold box has no holes

That's all we have for now, next month we'll talk about casting! The do's, don't's and everything in-between. Until then, get out there and make some mistakes!

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