I can't get this clear epoxy resin to be... clear

[4knflyin]

I've spent at least two hours over the past two evenings. Last night I started with #600, then #1000 and each whole 1000 until after #9000, where's there's a gap in the sanding sticks I use until #12,000. I started it over again last night and got to #4000, which is where I started tonight. Did the rest of the routine, plus Tamiya Coarse through Finish, and ended with Meguiar's Ultimate. The polishes were applied with a Dremel tool on the lowest setting (which is still pretty fast).

The material is Janchun epoxy resin. They practically have a monopoly on Amazon. Importantly, the 'glass' started out perfectly clear straight from the mold. There were two significant "air-holes" that I had to fill, hence the sanding. This is the back window on my 959 build, where nothing, but nothing, comes easy. I hope you can help. (The deep scratches have me scratching my head, but I want to focus on the milkyness.)

Here's an example of another part I cast with the same resin on the same day, Monday, I believe.

 

These are pictues of the window starting after #12000 through to Meguiar's.

This is after the #12000 sanding:

 

After Tamiya Coarse (about 2 or 3 min. per side):

 

After Fine:

 

After Finish:

 

And finally, an hour later, this is what it looks like now after using Meguiar's Ultimate

Edited January 20 by 4knflyin

[peteski]

Never used the stuff but going by all the surface polishing you did it seems to indicate that the cloudiness is within the material itself (not on the surface).

If you still think the cloudiness is due to the lack of surface smoothness, take some clear paint (actually "Future" or whatever it is called now would be best) and apply it to small area of the front and back of the windshield. Even clear nail polish would work.  The liquid clear will fill any unevenness and make the surface appear clear.

Edited January 20 by peteski

[Ace-Garageguy]

Well...this doesn't answer your specific question.

HOWEVER...there are much better ways to form replacement model car windshields and other windows than casting.

 

Edited January 20 by Ace-Garageguy

[stitchdup]

does it return to clear if you hold it under water? if it does it means your surface has damage but if not you should be able to build up coats of acrylic clear to get back the clear. also by using the tamiya course paste you completely undid all the polishing you did, the course is roughly equal to around 4000 grit so that might be part of the problem too. i'd be inclined to try toothpaste or plastic pvc window cleaner/polish on a micro fibre cloth after the 12000

[robdebie]

Since you state that the part was perfectly clear after demolding, you can rule out that the cloudiness is internal. My first guess is that the material isn't hard enough to be sanded and polished, it's too rubbery. You can probably find the Shore-D value somewhere. Maybe you can increase the hardness by a postcure, only then you get the full material properties. Room temperature cured epoxy isn't 'done' curing.

I've done some clear resin casting too, with epoxy resin. Shown below are the fuselage parts of the MPM 1/72 Fokker G.I Mercury. Epoxy is a killer for silicone rubber, shown in the second photo is the sixth casting, that came out cloudy. With polyurethane resin I get twenty castings.

Rob

[Mike 1017]

Rob is right about epoxy being too soft. I have used for "Slop Moulds" and sanding does not work out very well.  I use Createx Clear Acrylic it works out good.

Good luck

Mike

[4knflyin]

On 1/19/2025 at 11:07 PM, Ace-Garageguy said:

Well...this doesn't answer your specific question.

HOWEVER...there are much better ways to form replacement model car windshields and other windows than casting.

No, it didn't answer my question, but it was a pretty interesting thread. That specific solution would work because I don't care that the end result would be larger than the original. It's a simple rear window that can be cut to size. So thanks.

[4knflyin]

On 1/20/2025 at 4:26 AM, stitchdup said:

does it return to clear if you hold it under water? if it does it means your surface has damage but if not you should be able to build up coats of acrylic clear to get back the clear. also by using the tamiya course paste you completely undid all the polishing you did, the course is roughly equal to around 4000 grit so that might be part of the problem too. i'd be inclined to try toothpaste or plastic pvc window cleaner/polish on a micro fibre cloth after the 12000

I could have answered this right away because each time I rinsed it between sanding grits it amazed me how the water spots were crystal clear.  I have some Alclad Klear Coat that it says can be used for dipping. I've tested it, but on a part that wasn't representative of something like this. Hopefully to save me some grief, how do you deal with keeping the dipping solution from pooling along the edges? Anybody?

Here's some evidence:

Held above the water.

 

And submersed (this kind of says it all).

[4knflyin]

On 1/20/2025 at 8:30 AM, robdebie said:

Since you state that the part was perfectly clear after demolding, you can rule out that the cloudiness is internal. My first guess is that the material isn't hard enough to be sanded and polished, it's too rubbery. You can probably find the Shore-D value somewhere. Maybe you can increase the hardness by a postcure, only then you get the full material properties. Room temperature cured epoxy isn't 'done' curing.

I've done some clear resin casting too, with epoxy resin. Shown below are the fuselage parts of the MPM 1/72 Fokker G.I Mercury. Epoxy is a killer for silicone rubber, shown in the second photo is the sixth casting, that came out cloudy. With polyurethane resin I get twenty castings.

Rob

 

On 1/20/2025 at 10:03 AM, Mike 1017 said:

Rob is right about epoxy being too soft. I have used for "Slop Moulds" and sanding does not work out very well.  I use Createx Clear Acrylic it works out good.

Good luck

Mike

 

Great minds think alike? I had already started using ice cold water to rinse between grindings. Decided I would try sticking it in the freezer and holding it against some frozen peas to keep it cold — and hopefully solid — while I worked on it. I couldn't help but notice long ago that just holding thin epoxy resin casting for any length of time transfer enough heat from my fingers to turn it rubbery. When I saw your replies, I decided I needed to try my plan before replying back. So I did it and it was noticeably, but only slightly, better.

Mike, I checked out the Createx Clear Acrylic and I'm not sure I understand. You put clear coat in your molds to make castings? Or did you mean to mention this Createx product ($$$): https://sculpturesupply.com/products/epoxacast-690-clear

That stuff looks like the ticket. Does anybody have experience with it they want to share with us? For that kind of money (and I haven't even checked on the shipping), it would be nice to have more info, even if it was a vastly different application, before I do an experiment with it.

I almost forgot to mention, thanks for turning me on to that website. Thats a lot of stuff they've got going on that could be useful.

Edited January 23 by 4knflyin

[Deathgoblin]

How about using Gauzy Agent glass coat?  I watch a YouTube channel where the guy is restoring die-cast cars, and he uses this all the time on clear parts.  He'll sand them smooth, then dip and let dry. 

 https://www.amazon.com/Gauzy-Agent-Bottle-AK-Interactive/dp/B01GENKXSA/ref=sr_1_1?crid=7ZGTVRTQPNIU&dib=eyJ2IjoiMSJ9.woQ9yQyX1KheSz5-tGVXA0GLUa2AwPpOwZQTBwv3KhmZY7JNA_-iCYNNtFJxai3raWtmGn5ZkxhOvmV0tBb37Q7k7QGe2MEo7zWhFuqoIsk9PXKdQS7ZVp9xXEU40cwV.x4iNB3iepKYwg-iX2mLguonNMi6bMdhLWXEz8d5a0zo&dib_tag=se&keywords=gauzy+agent+glass+coat&qid=1737749996&sprefix=gauzy+glass%2Caps%2C75&sr=8-1

[peteski]

Since it was established that the cloudiness is due to microscopic roughness of the surface (the windshield is perfectly transparent when wet or under water), then coating the hazy windshield with any sort of clear coat should fill and smooth out those microscopic scratches, resulting in a windshield that you see when wet.  Back in the day a dip in the Future floor finish would have worked, but that stuff seems to be gone.  Any not viscous high-gloss clear coat should do the trick. I suspect that Createx Clear Acrylic is one such clear coating (I have not used it myself).

[Mike 1017]

I just ordered this today

Amazon.com: Bond Craftor Epoxy Resin Kit 16OZ, Clear Crystal Resina Epoxica Food Safe, Casting Resin for Art Craft, Jewelry Making, DIY