First time clear resin casting

[Rob de Bie]

This weekend I experimented a bit with clear casting resin. I had ordered 'Epoxy Crystal Clear Pro' from Silicones And More (NL). The first castings were very nice indeed.

 

 

This is how the kit part (MPM 1/72 Fokker G1) compares to the epoxy casting. I would say they are equal in quality.

 

 

I'm still learning how this resin works. The 10-hour pot life is extremely long compared to the 7 minutes of my polyurethane resin, and not useful. And maybe the resin needs a longer cure to develop its full properties. I probably released this part too early, and it shattered in a brittle fashion, just like clear polystyrene.

 

The moulds suffered a bit from having a chemically active resin for many hours. I would guess that the moulds would allow 5 castings, instead of 20 with my polyurethane resin. But it does open up interesting new possibilities.
 
 Rob

[dragonlanceHR]

Do keep us updated. Does that resin require any post curing?

I had great success casting the Gedeo Crystal Clear only to have the castings turn yellow and brown after a year. I think it's the humidity since they were all boxed out of the sun and heat.

 

Vedran

[Rob de Bie]

1 hour ago, dragonlanceHR said:

Do keep us updated. Does that resin require any post curing?

I had great success casting the Gedeo Crystal Clear only to have the castings turn yellow and brown after a year. I think it's the humidity since they were all boxed out of the sun and heat.

 

Vedran, I don't know the answer yet. The data sheet says a postcure is benifical. I accelerated the cure by floating the moulds in a bath of warm water (55-60C) for ~20 hours, so I may or may not have done the post-cure schedule. The brittle failure of one part tells me I did not do a full post cure.

 

Castings turn yellow and brown, that is a bad scenario! Your 'Gedeo Crystal Clear' is epoxy according to the internet. In my experience all epoxies yellow, but I never worked with an epoxy formulated especially for being clear, so I just don't know what's going to happen.. I've always understood that epoxies are not UV-resistant, so UV clearly affect the material, but I don't know how exactly. I'm planning to get some books on epoxies from the library, to learn more.

 

Rob

[janneman36]

I had a clear epoxy once and I needed a UV stabilizer in order from turning it yellow or brown and also to prevent crazing in the future..

Good luck Rob with your efforts and keep us posted!

 

cheers, Jan

[Rob de Bie]

6 hours ago, janneman36 said:

I had a clear epoxy once and I needed a UV stabilizer in order from turning it yellow or brown and also to prevent crazing in the future..

Good luck Rob with your efforts and keep us posted!

 

 

That makes a grand total of zero people so far with long-term success with clear epoxy.. Or did the UV stabiliser work out OK?

 

Rob

Edited July 21, 2022 by Rob de Bie

[Black Knight]

Another with negatives on clear resin casting

The resin I got had a short pot life, about 5 minutes, but an in-mould set time of plus 24 hours

After demoulding the resin was supposed to be put in an oven at 120* for further curing. But this turned the resin a tobacco yellow/brown

However, I found that putting the cast resin piece under my special heat lamp, which I use to fast dry painted models, for 7 days straight the pieces cured more but stayed clear

But they may not have cured 100% even then as I wrapped the pieces in kitchen paper and put away. Months later when I got them out the paper had stuck into the top surfaces of the resin. I can wet sand that out and micromesh them though

And the parts are brittle. Not so much the part itself as it is quite thick but the pouring runs and the fitting lugs on the parts break off too easily

 

I've got a new different clear resin to try now

[Rob de Bie]

Oh dear.. Maybe I'll sacrifice one casting, and hang it outdoors, in the midsummer sun, to do an accelerated UV exposure test (compared to indoors display).

 

Rob

[dragonlanceHR]

The thing is more and more aftermarket sets include clear resin windows and canopies. I wonder what product they use.

 

Edit:

The second thing is, a copy of 1/48 GWH MiG-29 windshield I did for a friend who cracked his is still crystal clear after 5+ years. But it was built in a week after casting and IIRC coated in Future or similar product, i.e. sealed.

Edited July 22, 2022 by dragonlanceHR

[Rob de Bie]

There are also clear polyurethane resins. But they are very finicky to cast, requiring long in-mould times and postcuring. I do not know how UV-resistant they are. My impression is that many casters try it at one point, and include clear resin parts in their kits, but hardly ever continue to do that. I concluded it's not practical for them.

 

At Telford in 2019, I accidentally overheard a man telling someone else that his supplier had removed the mercury from the clear resin's composition, and that he had nothing but trouble since. I think he mentioned spending 10,000 pounds on failed products, experiments and testing other moulding materials.

 

Rob

Edited July 22, 2022 by Rob de Bie

[janneman36]

On 21/07/2022 at 22:18, Rob de Bie said:

 

That makes a grand total of zero people so far with long-term success with clear epoxy.. Or did the UV stabiliser work out OK?

 

Rob

Never had it long enough on the model to get a conclusive result😇

[Rob de Bie]

I just put a piece out in the sunlight, to see what happens when exposed to summer UV levels.

 

Yesterday I tried working with the castings for the first time, and it was a good experience. The material was easy to use, roughly like clear styrene. I made various modifications to the parts, in an attempt to correct the shape of the fuselage pod of the old MPM Fokker G1. For the full story, see: https://robdebie.home.xs4all.nl/models/g1.htm

 

 

 

Rob

 

Edited July 23, 2022 by Rob de Bie