We get a lot of questions about the best ways to finish the resin kits we sell, so we put together a quick how-to on finishing a resin prop along with some of our favorite supplies to do so. (Note these tips apply to resin kits from any makers, not just us).
The first thing to do with a fresh resin kit is to cut off any sprues or their remnants. These are the pieces that stick out from pour holes or air spouts in the mold. You can use anything, but flush cut nippers. They will let you take off almost the entire sprue, leaving little additional clean-up to do.
Next, I take a blade–either a hobby knife or a snap blade depending on how big the prop is and how bad the seams are–and scrape. The seam lines are where the two (or more) parts of the mold came together. Depending on the quality of the resin casting, you may be able to skip this step (or you may need to do a LOT of scraping). But it’s exactly what it sounds like–holding your blade at an angle, just lightly scrape around the prop along the seam line. This will speed things along on the next two steps by quickly doing a lot of the smoothing work.
The next step, to do is round one of sanding. You will be doing many rounds of sanding if you want a nice, smooth prop, so be prepared. My current favorite way to sand is with 3M Sandblaster Flexible Sanding Sheets or Rolls. I use a combination of 100 and 220 grit for 95% of my sanding. They are great because they not only do a great job of sanding but because they have a rubbery plastic backing instead of paper, they seem to hold up a lot more to wet sanding. Speaking of which, we try to always wet sand. It doesn’t kick up as much dust (though you should still be wearing a mask), the sand paper will go further, and you will get a nicer finish.
Most likely, you will need to fill in some spots. Even the highest quality resin kits will need at least a few spots filled. Our previous go to (and what you see in the above photo) was Bondo Spot Putty. However, our new favorite though is the 3M Acryl-Green Spot Putty. It’s cheap, doesn’t require mixing, and does a great job of filling everything in nicely. It dries very quickly and can also be wet sanded. My first pass of putty is only to fill in the big, plainly visible stuff. Make sure your resin casting is relatively smooth before moving on to the next step.
Next up is priming the kit. The primers we tend to use are the Rust-Oleum 2-in-1 Filler and Primer and Duplicolor Filler Primer. A nice filler primer helps smooth out small imperfections quickly, it can be wet sanded, and most paints we use adher to them both well. You spray it on like any other primer, but it will actually fill in any scratches and pin holes. This is why we skip the putty on the small holes for the first pass. Once the primer is dry, you guessed it, wet sand it again. Once it’s dry, you’ll have a nice combination of primer and putty showing and you should be able to easily find any more places you need more putty. Now, rinse and repeat the above steps as many times as necessary until you have smoothed everything out and have a nice finish. We recommend a couple of final passes with finer sandpaper, like 600 and/or 800 grit before moving on to paint (even higher if you’re going for a mirror finish). This will still give your paint something to grip on to, and will make for a nicer finish.
As for paints, we prefer acrylic paints because of the easy clean-up and we try to reduce our use of harsher chemicals when we can (but still wear a mask when spraying even acrylics). We mostly airbursh with Tamiya acrylic paints, but they can also be brushed on. Depending on size and detail, we also use a wide variety of rattle cans. After the joy of the masking and painting dance, we seal everything in with a clear coat. We’ve tried a lot of different ones, but one of our favorites that balances quality ,finish, and cost is Varathane Polyurethane. It’s intended for things like wooden furniture, but it gives a really nice hardy clear coat on plastic props! It comes in both Glossy and Satin.
If the prop does need a super gloss finish, we have a final, final step and that is to finish it off with some Turtle Wax. This will help protect the finish from most scratches. It’s also a nice way to replenish a prop if it has some minor scratches in the clear coat. Apply the wax with a sponge or buffing pad, let it dry, then buff it off. You’ll have a nice shiny prop, all ready to go!