Embedded Files
you will need:
base with an adhesive topping
mold enclosure-- for best results, a rigid and non-sloping container is best. We will be pouring the base and cap separately, so either pick something you can cut away and then replace, or something you can wiggle the mold out of. Non-sloping sides will help keep the silicone from leaking over the edges.
Pour slowly-- a thin stream of silicone helps it get into all those nooks and crannies of detail!
1.To make a capped mold, follow the normal silicone mold instructions until you have a "finished" mold. Use a sticky base to make sure the model is strongly adhered to the bottom so no silicone gets under it. (that's the cap's job!)
Tip: for the first pour, the side facing "up" will actually end up being the bottom face on the finished product. Keep this in mind if you need to align colors or inserts when casting!
2. Once it's cured and you've peeled off the enclosure, your model should be surrounded on all sides except the top. Don't take your model out!! Displacing the model could result in a silicone leak that ruins the inside. We only want the cap to capture the last, bottom surface of detail.
3. First, you may want to clean up the edges. Espcially if your model has rounded edges where the cap and bottom meet-- use an exacto knife to carefully slice off and thin, wispy layers of silicone that overlap the edges. Keep the cuts straight and clean, as the mold will copy the imperfections.
4. Next, cut some register slots into the mold. Using an exacto knife (With safety glasses AND on a cutting matt, don't gouge yourself or the table!) cut out triangles or rectangles from the edges of your mold, careful not to interfere with your model. These notches will form mirror nubs on the cap mold. These are essential as they will help you put the cap on perfectly each time! Without them, it will be very difficult to align the cap on when casting.
Tip: cut one notch in a different shape than the rest. this makes it easier to align the cap when casting.
5. Most importantly, we have to prep the silicone so it doesn't stick to itself. We do this by covering the silicone only in a thin layer of petroleum jelly. Use a q-tip or a corner of a towel to spread it over the top and into the registers -- and if you want to be safe, over the edges of the base as well. You don't need a thick layer, but make sure you have good coverage. Be smooth, don't leave chunks.
6. Once it's spread, go over again and, precisely as you can, wipe off any the cream that may have spilled on your model. We want it to be able to touch the model and get all that good detail!
7. From here, follow the standard silicone instructions. Re-enclose your mold, pour on a layer-- generally you need as little as a centimeter of thickness for the cap (it's not structural) and cure it as usual.
(You may do this before or after the petroleum jelly as you see fit)
8. Your cap is cured!
Unfortunately, a little may have dripped down the edges. Not to worry-- a little jelly would have helped, but either way, you can use an exacto knife to carefully cut the seam apart. If you pull (gently) at the cap, you should get a feel for where the edge is. When in doubt, cut low and slowly work up until you find the edge.
The cap should lift pretty easily, though you may need to help it along with additional cuts. Don't try to yank it off or you may rip the silicone.
Be mindful of the register notches you made-- you'll have to cut around them or risk losing them!
You're ready to start resin casting! Pour as usual, but be extra careful to fill up all the nooks and crannies as there will be even less space for air bubbles to escape.
We also recommend pouring a bit of extra resin on top of the base to squish under the cap-- you may have to sand some edges off, but it'll help reduce large gaps in the top surface as the resin degasses and sinks.
Press the cap on firmly and sent it in to cure!
Page updated
Report abuse