Hey there, this post was made for some people on Reddit who were asking me to explain what my new adjustable box was for. Basically the box is made out of four L shaped pieces of veneered chip board that myself and my Dad put together as a bit of an evening project. When lined up like shown above, they can be adjusted and moved until you have a box the right size for the piece you want to mold. I snagged the idea from Smooth-On’s official video tutorials. They use expensive clear acrylic ones, but, not having that kind of money, scrap chipboard does me just fine.
Anywho, I attempted to explain on Reddit how to go about the molding process, but sans pictures I can understand for people who haven’t the foggiest as to what I’m talking about, it can get so much more confusing. So to test the box works, I decided to mold a piece I needed for next week, and document the process over the next 48 hours for people who’re wondering what the hell I’m up to.
So, #1 use for an Adjustible Box is to make a 2 part block mold. To start you need to decide where you want the seam on your piece to be because there will be flash on the edge to deal with. I’m molding a flexible waste pipe which is even all the way around, so a seam halfway down the middle is fine for this. You start by packing the sides with clay and build up and even base all around and right up to the piece as show in the photo. Normally for this type of item a 2 part thixo mold (which uses a lot less silicone but requires a hard shell) would be better, but like I said, this is for demonstrating purposes, and I needed something large so you could actually see into the box. Because it’s a tube I blocked off both ends neatly with clay so silicone doesn’t seep in there, and once I had the clay base done I added in keys along the side so when I have 2 sides of the mold, there’ll be a locking system to keep them aligned. Because the tubing itself is also made out of silicone, to stop the molding silicone fusing to it I coated it in some One Step which is a sealant and a release agent which will create a barrier between the tube and the mold silicone.
So after draining my tubs of Oomoo 30 (I used what’s in the pic + 1 full cup for this) which is a 1:1 molding silicone made by Smooth-On, I mixed it together until it became a uniform purple colour. This was then poured into the mold and allowed to even out. Oomoo 30 is super viscous silicone, so it doesn’t require degassing in a vacuum chamber which is handy for me because I don’t have one at home. All the bubbes rise to the surface and you can give it a little extra tap to encourage the bubbles to rise too. Oomoo 30 takes 6 hours to cure, so I’ll update when it’s time to remove the clay and flip it over.
UPDATE 1: I was supposed to update this with the second half today, but in the hectic day I had I stupidly left my camera in the studio, so it shall have to wait until tomorrow! Sorry!`
UPDATE 2: Sorry for the delay, so the next step with the mold, once the silicone had cured was to remove the L shapes and take the mold out. I flipped the mold over so the clay was on top and removed the clay from the mold. Clean the silicone from around the piece, careful not to remove the piece from the silicone which will break the seal it has on this. I made this mistake when trying to get all the clay out, breaking this seal allows the silicone to slip under an destroy your mold so it’s vital you keep that seal.
Once all the clay is removed make sure you use a sealant again to stop the silicone sides sticking to each other then you add a new batch. Replace the L shaped sides again tight, but without warping the bottom layer of silicone. The second batch of Oomoo 30 was mixed again and poured. Ideally when this silicone was cured I would separate the two sides, remove the tube, and use the mold to slosh cast the shape I needed. But due to my breaking of the seal between the first side of silicone and the tubing, silicone got under the tube, and pushed the tube up out of the way so the mold needs to be remade. The best way to learn is by making mistakes, so this mold will be made again, but hey, at least my adjustable box works!