I've this isn't the first time you stumbled upon my blog, you know I have made a few customized sketchbooks. I've got this cool technique to make imitation leather, that's both a lot cheaper and easier than using real leather. If you want to learn about it, check out this post (this was my first book project, wich kinda failed, but it explains the technique nicely and I don't want to explain it again every time, so I just refer to this post).
Another thing I add to almost all of my books is some sort of cover ornament. Corners, symbols, all sorts of stuff. Until now, I always made them out of cardboard or MDF, but these thingies take a lot of time to make, much more than you'd think. Since I sell these books in my Etsy store, I should charge an insane price if I want to take into account the amount of time that goes into making one.
To speed up the process a little bit I decided to make molds of my cover ornaments, so I can just cast them in resin. Also, it makes it easier to make multiple copies of one book and keep my store stocked. Until now, after a book was sold, I had to remove it from the store.
So let's get started! I made some ornaments like I did for my other books, and then made silicone molds from them.
Materials
- MDF scraps (I never throw leftover away, they come in handy for stuff like this)
- Coping saw, files, sandpaper
- PVA and cyano acrylate glue
- Acrylic gesso and paint
- Sand (more on that later)
- Foamcore board
- Hot glue gun and sticks
- Release spray
- Molding silicone
I made four corner ornaments, four clasps for wrapping straps around the back of a book, and an Elder Sign sigil. This involves a lot of cutting, filing and sanding.
MDF doesn't really hold a sharply defined edge very well, especially thin MDF. There's a trick I learned from Bill Doran at Punished Props, though. If you apply cyano acrylate glue to the edge, it becomes very hard and keeps a good edge much better. Use thin glue for this, not the gel type, so it soaks into the fibres. After it has dried, you can sand and file it much better. Oh, and it never hurts to keep a bottle of acetone near when working with super glue. I managed to glue my fingers together on more than one occasion...
I wanted to give the Elder Sign sigil a textured background. I sprinkled coarse sand over it, smoothed it out as much as possible, and then dripped watered down PVA glue over it, soaking the sand with it and glueing it in place.
Before making a mold, I painted all pieces, first in gesso primer and then gray paint, and sanded it between each coat. Painting it makes it easier to spot any flaws.
Molding
When my ornaments were ready, I made molds using silicone. There are two kinds of mold making silicone: tin cured and platinum cured. Tin cured is cheaper, but it shrinks a little bit (not much, and usually not really an issue) and has a shorter life span; after a few years, it will start to deteriorate. Platinum cured silicone hardly shrinks, but it is quite sensitive to cure inhibition. Certain kinds of clay, glue and paint prevent it from properly curing. Most of the time, tin cured will do just fine.
The type of mold I made is the simplest type, a flat-backed box one part box mold. To construct the box, I used foamcore board and a hot glue gun. Foamcore is strong enough to build a molding box, but easy to rip apart after the silicone has cured. To make sure no silicone creeps under the ornaments, I glued them to the bottom of the box using PVA glue. And even though it's not strictly necessary for silicone, I applied some mold release spray.
Next, I mixed up some silicone and poured it into the mold boxes. To prevent bubbles (and if you don't have a vacuum degasser chamber), pour it from high enough, so the stream gets stretched out and most of the bubbles pop. It's best to pour it in the corner of the box and let if flow over the items, instead of pouring directly on them.
The next day, the silicone had cured and I liberated the items from the molds. They turned out quite ok, without any visible flaws. I already made a few casts using polyurethane resin, and it works perfectly!
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