Transparent finish for hollow parts


What ratio(s) of resin to IPA have you tried? I imagine the finish depends on how quickly all of the IPA evaporates. Also, did you cure the part under UV LEDs or let it cure in its own?


In the first experiment I added just enough alcohol to make the resin noticeably thinner. That yielded produced the finish shown in this picture, shiny but uneven with a raised ‘pimple’ nearest the camera.

Today I tried again, taking careful measurements. I mixed 8.0 grams of resin with 4.1 grams of isopropyl alcohol. It stubbornly refuses to cure, so apparently that was too much alcohol. Or maybe I need to a different thinner, something other than alcohol.

I’ll leave it under the UV curing lamps and see if it ever sets up.


Have you thought about trying Isobornyl acrylate (IBOA), which is used specifically for thinning UV resins?

I have a bottle, and will be thinning out samples of Formlab’s resins to use in an airbrush. I am hoping to spray on a coat of thinned resin on a print, then cure, then repeat a few times to hopefully get a glossy finish without polishing.

At the moment, I finish off a cured print with extremely fine grades of sandpaper, (up to 12,000 grit), and I do get a mirror polish, but I can’t get into the detailed bits.

(Although I have scratched the iGoo project box since).


This looks absolutely amazing! It does look like a finished real product. Can you please share the steps you used to achieve such a result?


As far as polishing to a high shine find some micromesh polishing cloths, it’s basically cloth sandpaper and it does a really great job.

Just remember to start with a low grit and move up, if you jump too far then you’ll end up with a polished part with some large scratches because the higher grit doesn’t remove much material.


What Zachary_Brackin said. :slight_smile:

Here is a link to the Micro Mesh NC-78-1 restoring kit that I used. It is not cheap, but it gives great results and contains grit ratings that I had never seen before.

Here is a link to a video that shows the process and finish you can get with their kit of ultra-fine sandpapers.

Also, whatever program you are using to create your curved models, make sure that you view them in ‘flat’ mode, as that is what your print will actually look like. 3D programs usually mathematically smooth out the appearance of the model for rendering, but that does not affect the geometry, which is what PreForm will be printing from.

Organic shapes need a lot of triangles, so I subdivide my surfaces until there is no visible faceting when I zoom right in. That way the model prints very smooth, but with a slightly dull finish after curing. The micro meshes kit brings out the shine.

I spend a lot of time on finishing as I make a mold from the print. I can then create many copies, quickly.


Thank you so much Macro! I have been using Blender for about 7~8 years and I’m well familiar with flat vs smooth shading. I always subdivide my model to level 3 or 4 to make it as smooth as possible to make the sanding and finishing easier.

Will check out the video and the restoring kit. Thanks again :grin:


aad345, I am a Blender user too, brother. :slight_smile:


The different finishing options here are amazing. Definitely want to try a few.

@Dudemeister XTC is a 2 part epoxy. It is well advised to mix and use it in a ventilated area. If you do that you will be ok. I haven’t seen the need to for a mask or anything like that if you are in a well ventilated area.

I will try curing a print straight from the printer and then putting some XTC on it and see what results I get.


This is one of the reasons I love this forum, you just learn soooo much from people around here.


I use a lot of smooth-on products - those guys rock!


If you guys want an extremely clear part you may want to look at casting from a printed mold. I use Alumilite because they’re local but Smooth-On makes good stuff as well. If you can pressure cast it will be near perfect with a good mold and the material is cheap so no need to shell it out.


Wow I checked their website and saw the video on this page and it is veeeery clear. I should order some and try to make a few things with it.

Thanks for sharing this man :smile:


It’d be interesting to see some results from castings–it’s possible that a casting will still end up not having a clear finish since the issue on the printed part is that it has a rough surface which could still translate into a cast part.


True. It will have to be fine sanded and polished before getting such a clear surface finish.


I normally use spray lacquer to get a nice smooth finish on the molds. Just enough to wet the surface is all I normally need.

If you’re going to use a printed mold it’s very important to fully cure the material. If it’s even a little bit green your casting material won’t set properly. The lacquer also helps prevent this.