Achieving transparency with clear resin

I’m going to try something that I believe is new, wish me luck. We have a large model (230 ml) that we would like to have as transparent as possible as it is a prototype of a part that will be produced in clear acrylic. Previous iterations have come out of the printer (0.10 mm) quite transparent, but after the wash they are translucent and foggy . I’m printing the next one at .05 mm and I’m going to put it directly into the cure chamber. I had to add handles, that don’t touch my model, and use a raft. Hopefully they will enable me to remove the entire print, raft and all, from the platform and get it into the cure in a single piece. I’ve cut a circle from a silicon baking pad to prevent the raft from sticking to the cure platform. Logic says that it will work, but the proof will await the tests A lot of things have to come together. I’ll report the results, but images will have to wait for word from our Patent Attorney,

I was reading other posts re: Tray life and I’ve decided to change to 0.10 mm as a precaution. A successful print will let me know if I need to go smaller next time.

If you are going to cure this without washing in IPA I would make sure it drains for quite a while, maybe overnight, to get as much liquid resin off as you can.

I’m planning just the opposite. I want as much resin on it as possible. The idea is to let the printer apply the gloss coat. The silicone pad should help.

Hey there,

Good luck with this!

The two main techniques for achieving transparency are polishing or coating[/dipping]. I’ve played with both. Coating (as you’re essentially doing) can be effective but I found it difficult to get an even coat - especially near whatever corner the excess resin drips off from. I have a small, flat part and was thinking of some kind of centrifuge type setup (or spinning disk) to help with that…

Let us know how it works out.

The parts are tubular. I came up with a method of coating them, but it is complicated. As I said the printer seems to do a pretty good job of coating the part, in and out, so I’m going to give it a shot. As my son just pointed out the IPA in the wash is 9% water (more as it evaporates) and I’m sure that doesn’t help with transparency. I just started the print so about noon tomorrow we’ll do the first test.

Better for my purposes. I was late removing the print so most of the resin drained off. It took 6 cure cycles. Be sure and use a silicone pad! That is a piece of paper loose on the inside.

I have achieved water clear parts- its pretty easy-
First do a water cure- or even better- use Wicked Engineering’s CUREGEL to post cure the resin without any oxygen exposure-
then sand the surface starting with a pretty smooth paper- like 320 or 400 and work your way up thru 600 to 1200 or 1500 grit paper.
clean the surface well- and then apply a coat of gloss clear acrylic.

what you should end up with is perfectly clear.

However- you will have to do BOTH sides of the part. the part I made was a negative space bas relief portrait. so there was no way to sand the negative space of the portrait perfectly smooth- instead, the front and the back of the print were flat planes and the portrait relief was a negative cavity in the back side of the print. I painted the relief an ivory color- after sanding the front face and rear face smooth and then sprayed the gloss coat overall.

this looks like an embedded cameo- but the image is actually a cavity in the back of the printed plate of clear resin… I painted the inside of the negative space in the back so that it would appear as a solid positive from the front.

This was printed at 25 microns and the bust could not be finished- that’s how good the surface was straight from the printer.


A true work of art, nice job! Interesting technique, but unfortunately it won’t work for me. My part virtually uses the entire available build volume and is 6.0" tall before the supports and raft are added so 25 microns isn’t in the cards. It’s not just the time required, almost four days, but the wear on the resin tray/tank. My method is OK for our prototypes. We will soon contract for a manufacturer to make our production pieces in large quantities. Again a beautiful piece!

You can also wash and cure as normal, then apply a thin film layer of clear resin by simply rubbing resin on the part with a gloved hand, or in the nooks and crannies a tiny brush. I use dental composite applicators, then cure for about 5-10 minutes. Another trick is to do the above, then drop the parts into water inside a clear container. This will prevent it from developing a oxygen inhibited layer. Place the container with the part submerged under water into your cure unit… The cured parts will definitely look much clearer. I’ve used this technique many times myself for parts that I want to be transparent. Most of the time, you won’t need the water if you keep the layer thin.
Best of luck!


The best results I’ve gotten are simply from sanding it smooth, using water starting from a low grit to a very high grit, but it takes hours to do. I’ve found the resin is too thick to do a good even coat on the part.

Formlabs used an autobody painting company I believe that used a higher grade spray on clear coat thats harder to scratch then anything we buy at the hardware stores…In my case Im going after solid fine art finishes so things that scratch or chip or show any sign its been sprayed on wont work. Im really intrigued into the water cure method for retaining clarity now. Sanding is tedious and impossible in some ways as well as loses details which is its con…but it actually smooths the microscopic surface and is hard to beat for alot of reasons. Id definitely be interested in a renewed inspection from formlabs about this if they’ve learned anything!

I told you guys that I would post a pic if it worked. It serves my purposes, so… The top section was washed and cured, the bottom was carefully removed from the build platform, placed on a circular piece of a silicon baking pad and put directly into the cure chamber. It came out pretty much like I thought it would. Let the print drain very well to avoid runs and put it in the cure chamber platform side up.