Resin Pyramid Casting Tips
Updated: Apr 3
Casting in large pyramids, can be a bit different then casting in smaller flat or shallower moulds. Here are a few tips, that might be helpful for when creating resin castings in pyramids. Plus I have added a few more tips if you have a pyramid that didn't come out as nicely as desired.
Please NOTE: If you are planning to cast "florals or organics" in a pyramid, there are additional factors and processes you will need to read about for floral casting as well. Those are covered under a different blog post about tips specific to floral (or organics) preservation casting.
To ensure your apex (tip) comes out correctly (and not with an air pocket on top), pour a tiny amount of resin in to the mould, then take a toothpick or skewer and gently touch the point in the apex of the pyramid, pushing some resin in to the tip, and carefully move the resin around a bit to ensure there are no air bubbles sitting in that point. Watch for any bubbles to float to the top, and if it does, then pop it. Then pour the rest of the resin you plan to use for that layer, in to the mould.
Never ever ever use a torch to remove bubbles in your pyramid moulds. This can cause the mold to fuse to the pyramid casting, and when trying to remove (unmould), can rip your mold. (Yes, I learned this because I made this mistake years ago ;)).
Ideally, ensure your resin has no to low bubbles "prior" to pouring in the mould. Once some is in the mould, wait about 10 minutes, and if you see any bubbles, ideally try to pop them manually with a toothpick or needles. If needed you can lightly spray a fine mist of isopropyl alcohol (ideally 99%, but any over 90% will work), over top of the resin. Be aware alcohol can shorten the life of your moulds. You may need to repeat popping bubble process in 10 minutes, and possible repeat in 10 minutes again. Depending on items being added in to the resin, you may need to babysit bubbles for awhile. You can also pre-coat said items with resin, prior to adding in to the mould, to assist with bubble reduction.
In order to avoid air pocket bubbles on the sides of your pyramid casting, after you pour resin in the mould, (for each layer), gently move a silicone spatula or popsicle stick along the sides to push off any surface bubbles you may not see sticking to the sides of the mould, and as they rise to the top, you can pop them.
Never fill your pyramid to the top of the mould. If the resin leaks out over the top it can be hard to separate the two piece moulds once resin has cured, without ruining one part. There is another reason for this discussed below.
After demoulding, if your pyramid has come out with air pockets on sides, or some errors on it, you have a few options to fix it. Due to its shape, it is not easy to topcoat each pyramid side once it has been taken out of the mould. Painting the sides with resin often results in ugly drips running down the sides, sometimes making the piece worse then what you started with trying to fix (ask me how I know ;)).
Option A: Latex/or Elmer's glue. If a person has the patience, they can paint elmer's glue or latex (if selling piece make sure customers do not have serious latex allergies), on three sides and bottom of pyramid. Use a level, and try to set the pyramid on a perfect angle so top side you will be brushing with resin, will be flat and level, then pour resin on. Peel off glue/latex once resin has cured. Any resin that dripped over the sides, will peel off with the glue/latex.
Repeat process for each side requiring the clear coat. This is a slow process that takes days, because you have to let each topcoat on each side cure thoroughly, before working on next side. Not an ideal method.
Option B: Double-dip. Another reason never to fill your resin to the top of a pyramid mould, is if you do need to use this option to fix any errors on the casting, you will be glad you left a bit of space to allow for a double-dip of the piece. Lightly sand the sides of cured casting, and remove dust in the holes, then wipe remaining dust with isopropyl alcohol, then let dry.
If there are air pockets that get filled with sanding dust, you may need to use canned air to blow the dust out of the holes, or a toothbrush to scrub out the dust before attempting to double-dip piece back inside mould.
To prepare for double-dip, before setting pyramid casting back into the mould, coat all the sides of the pyramid, and inside the mould with resin. Depending on size of pyramid and casting, fill mould with about 1/4 to 1/3 resin (this may take a bit of practice to figure out). Have a spare coaster mould ready, in case you poured too much and need to tip a bit back out again. It is messy, but if covered well, your piece will come out beautifully, and all previous errors should be hidden by new resin coating. Leave to set/cure for longer then usually required to ensure fully hardened prior to unmoulding the double dipped piece. Thin layers can take longer to cure.
Note: Just pouring resin in, without coating all the sides of both pyramid and mould, can cause a patchy double-dip, requiring heavier sanding and re-dipping all over again. (Or in my case, it was so bad, I smashed it to bits, to use as filler another time. lol. Thankfully, in that case, it was more of a test and not a commission, which would have required taking the extra steps to fixing.)
Option C: If you have the tools, you can sand and polish your pyramid to a beautiful finish as well. But it will take some elbow grease. Many people prefer the finish of sanded and polished pieces, and some types of resin crafting are all finished with that process. There is a separate blog post that covers options for sanding, buffing and polishing.