Flexible 80A clear coating for better transparency

Hello. I am looking for a way to make a part printed with flexible 80A more transparent and with a better finish. I want to be able to take a picture, under the microscope, of a metal piece placed inside a tube with 1mm (0.0394 in) wall thickness and 3mm (0.118 in) inner diameter.

I have tried placing the part under water and filling it with water, but the result is not great. I have tried both 50 and 100 micron layer thickness, 50 being better, but still not enough and took too long to print. I also tried printing at different angles.

The only thing I found online was sanding the part while frozen for removing the support points, but I am thinking of a coating that I can apply on the outside of the tube that will still maintain its flexibility.

-Does anyone know or tried anything?
-Does clear acrylic spray paint work ( do I need to sand the part first? )? I know that it is used for parts printed with clear resin.
-Or maybe submerging in oil ( what kind of oil? )? But for longer parts this might be hard.

In a couple of weeks I will try Elastic 50A, but might get same results.

Hope to hear any advice.

Thank you for your time.

As you’re using Flexible 80A I expect you need it to be erm… flexible! You could try brushing on a little of the resin (perhaps thinning it first with some IPA then letting it evaporate off) then exposing it to 405nm light or just exposing it to natural daylight. I’m not sure where you are in the world but we have a product called Plasti-Dip here in the UK. They do a clear version as well as a ‘glossifier’. You could also try a clear mineral oil (like baby oil).
Hope this helps.

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Thank you, @mrwakefield! It was very helpful.

For anyone interested, so far I have tried the thin layer of resin trick and it is an improvement. At the moment I am trying different curing times and temperatures (using the Form Cure machine), as I am doing this layer after the initial cure.

I will try to get some mineral oil as well (it might help for the inside finish, being harder to apply a thin layer of resin on the inside of the tube).

You’re welcome, I’m glad it was of some help. You might like to buy yourself a 405nm laser pointer to cure the resin coating as that’s almost instantaneous. If you find the surface is still a bit sticky you can try submerging the part in water and expose it again. The water eliminates the oxygen which can inhibit the cure that leaves the surface sticky.

Yes, I thought you might have to use a different option for the internal surfaces. An alternative to mineral oil might be petroleum jelly (Vaseline) or silicone oil, not sure whether this would behave any differently but it is available in various viscosities as well as a grease.

I think going with mineral oil its a good start, I have not done this on flexible resins yet but my go to item for shining up surface after sending is plastic polish, there are many products available on the market from single to multiple stage and sometimes I will use “Novus” but believe it or not my daily favorite go to is Armor all restorer lol it works! (but it will not make clear look like lens though, it’s not magic :stuck_out_tongue: )
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Thank you @jantarek for the advice. I have looked into ArmorAll and PlastiDip (which as suggested by @mrwakefield), but in the end I had to say pass to both of them due to the chemical composition (not compatible with my application).

To give an update to anyone interested, I have tried adding a thin layer of resin and had some interesting results:
1) applying the layer of resin on an already cured object, curing then using different settings for the Form Cure (time and temperature); RESULT - always sticky
2) applying the layer of resin on an already cured object, curing again using the standard settings or 80A (time and temperature) and then water curing for half the time recommended (10 degrees lower); RESULT - better, but sometimes bubbles would appear and started to become sticky after a couple of days, especially if you wiped the surface with water (to take the dust away)
3) applying the layer of resin on an uncured object and then curing the whole object using the recommended settings; RESULT - good transparency, non tacky/sticky (just make sure you get a uniform layer, which feels impossible on a round surface)

A way of thinning the resin and to avoid bubbles (which can be appear when using IPA) is to heat the resin. I did that by placing a small container with some drops of resin in the Form Cure, setting a temperature of 60°C and stopping the process when it reaches approx. 55°C (so the small container with resin was not exposed to the UV light).

Curing the thin layer at the same time with the part was an obvious option, but I wanted to make use of the prototypes I have already cured, maybe it would have be possible to get a good result. Furthermore, the process was not complicated for me as I only had to highlight a certain area of the object, which also helped in seeing the difference between the altered and non-altered sections.

In dentistry we use glycerin to cover the oxygen inhibited layers of resins(fillings in some cases) so that once cured the surface is tack free. Although, his means that secondary bonding and chemical interlock will no longer be possible on that surface.