Pouring 2-part epoxy resin directly on foam?

[denny99]

Is it safe to pour 2-part epoxy resin on properly acrylic-primed and acrylic-painted foam?
If not, any other idea to cover the foam? Maybe with a thin sheet of styrene cut to size?

The riverbed I am building is fairly square and straight, as it's a portion of the LA river in San Fernando Valley, CA area.

[Allen]

Not sure if the epoxy is too hot or not Denny? You could apply a test coat on a scrap piece. If you paint it I'm sure it would be OK?
If it's an acrylic mix it might be safe?

If you have any concerns about, you could always use the stuff I used on my bog and plan to use on my Ouachita river soon.
It's 100% acrylic and a one part pour.

[denny99]

Thanks Allen! I’ll give it a try on a scrap piece. If it doesn’t work, I will certainly look into the Liquitex gloss medium.

[john_plsn]

I did it with no adverse effects. As long as you have it sealed where it won't find a way to drain you should be good to go. If your not sure put down some plastic trash bags just n case it finds a way out. Thin layers seem to be the best way to avoid issues of it finding a way out.
Here are a couple examples of me throwing caution to the wind.

[denny99]

John and I share a similar avatar, but that is all John’s work, Paul

I have yet to test the resin on a scrap piece, and I’ll be able to in a few days as I am on my way to a business trip to Spain in a few hours.

[denny99]

Thanks for the tips john_plsn your work looks awesome!

[Paul S.]

Oops, my bad, John and denny99 . Correction made.

[denny99]

I managed to complete a test on a scrap-piece.

• I made a mini-version of the riverbed and banks
• then I painted it with white Vallejo primer
• painted the riverbed a mix of blue, brown and green color
• added a few drops of Vallejo Dark Olive Drab to the resin mix
• carefully poured the resin

The result is pretty convincing, in my opinion. I can spot a few cracks in the primed surface, so maybe I should paint one more primer layer. But overall, the foam didn't melt and the resin I used seems to be of good quality.

[denny99]

Thanks, Allen!

[BillyJoeBob]

denny99 -- That sure is smooth! That's the kind of surface I want on the water of flooded pit mine. What kind of resin did you use? Thanks --- BJB

[denny99]

Thanks, BJB! It's a clear 2-part epoxy resin, nothing fancy. I got it on Amazon with low expectations, but I am really pleased on how it turned out.

[denny99]

So, test on a scrap piece went great. Onto the real one!

I started priming with the same Vallejo white primer, but this time the surface to paint was much larger (about 3x). So I got bored quite soon and I had what I thought it would have been a GREAT idea.

Why not using a cheap white spray can to lay the basic paint? It's a lot less time-consuming, and the thickness of a spray can layer of paint should be more than enough for the subsequent layer of paint and ultimately the resin.

I started digging in my box of unsorted paints and there it is: a flat white, fast drying, spray can. Half full, but ready to be used!

I sprayed a thin layer, then added another one right away. Oh, the result was amazing. In less than 40 seconds I primed the riverbed and riverbanks. Awesome.

I let the thing dry for a few minutes and I started noticing a few bubbles. Well, "no worries", I said to myself "I can sand it later and fix it with a quick layer of the same paint".

After 10 minutes I realized I probably had to rebuild the foam riverbed from scratch. After 15 minutes I came to the conclusion that I had to redo it all.

The paint melted the foam! I was worried about the resin, but in the end it was the paint. And all because I wanted to complete the task in a hurry





I managed to salvage the riverbanks, that surprisingly weren't affected by the paint (different kind of foam board). I assembled a new riverbed, and painted with good, old acrylic paint. Hopefully this weekend I'll finish the project.

[denny99]

Yep. But I'm going to win this battle Ready for another round, now!

[BillyJoeBob]

denny99

Back in the day when the earth was young, lakes, riverbeds and the like were cut from plywood and set in place on the framework using risers.

BJB

[denny99]

I almost want to fall back to plywood, BJB

[Paul S.]

denny99 said: "The paint melted the foam! I was worried about the resin, but in the end it was the paint."

I'd almost want to laugh it were me in your place, Denny. Almost.

What a bummer!

[denny99]

Let's just say I took it well. 😂

[denny99]

This past weekend I re-did the riverbed, painted it and poured another layer of resin. I then added some ripples using a gloss acrylic gel, dabbing it with a brush.

To be honest, I am not 100% satisfied with the result. I like the color, not the texture. Also, there are a few bubbles I didn't catch right away and fix. However, I managed to hide them with the gloss gel.

I'd really appreciate some honest critique before I throw everything away and start over Here are a few photos where I test-fitted the riverbed and a basic bridge support.

[Cody]

The wider angle pictures look like fast flowing water to me. The first, more zoomed in pic is OK... not perfect (I can't quite put my finger on it) but still good.

[denny99]

Thanks for the feedback, Cody. Yes, it gives the idea of a fast flowing water, and the LA river it's not - at least in Burbank.

[Paul S.]

I see what you mean about the texture, Denny. Stipling acrylic gloss gel does tend to create a busier water effect than applying acrylic gloss medium with smooth brush strokes does.

That said, perhaps the Los Angeles River is roiled on account of an overnight thunderstorm up in the Santa Susana and San Gabriel mountains?

[Allen]

As the others have said Denny, overall it looks good, but I see what you and the other have said, it looks like it has too much of a chop on the surface.

What if you redid the pour, on current sample, repour enough to cover up the existing water so that you wind up with another smooth surface (or start over).
Then....you want to show movement, but not a chop. Try this for a rippled effect:

Start at about 3:43: https://youtu.be/OFc4FDACM_4?si=P9NadpVIu7WCqApZ

Kathy uses a Tacky Glue to make ripples and then knocks them down a bit using the nozzle or toothpick.
Not sure if that is what you want or not, but it looks like a good method for a good effect?

But this comes from someone who knows not much more about water scenes, lol

[denny99]

I see what you mean about the texture, Denny. Stipling acrylic gloss gel does tend to create a busier water effect than applying acrylic gloss medium with smooth brush strokes does.

That said, perhaps the Los Angeles River is roiled on account of an overnight thunderstorm up in the Santa Susana and San Gabriel mountains?

Plausible, but unlikely I guess 😅

[denny99]

As the others have said Denny, overall it looks good, but I see what you and the other have said, it looks like it has too much of a chop on the surface.

What if you redid the pour, on current sample, repour enough to cover up the existing water so that you wind up with another smooth surface (or start over).
Then....you want to show movement, but not a chop. Try this for a rippled effect:

Start at about 3:43: https://youtu.be/OFc4FDACM_4?si=P9NadpVIu7WCqApZ

Kathy uses a Tacky Glue to make ripples and then knocks them down a bit using the nozzle or toothpick.
Not sure if that is what you want or not, but it looks like a good method for a good effect?

Interesting, thanks Allen! Yes, I think I used too much gel, and dabbed it without movement.

I actually tested the gel on the scrap piece I used to test the resin. Undiluted, semi-diluted and diluter. I used water to thin the gel.



Undiluted version clearly has nothing to do with a river or canal, unless maybe it's a river with rapids. It feels more appropriate for sea water.

Somehow, I preferred the semi-thinned gloss gel, and used it on the final riverbed, while it's clear I should have opted for the thinned version. I diluted the gel 60:40 (water to gel) and dabbed it very gently.

But this comes from someone who knows not much more about water scenes, lol

😂 Yours looks great!

[Allen]

Denny, I think the thin glossed Gel is the one to go with? It's very subtle, yet shows some amount of movement, either from a breeze or movement of the actual water. Possibly another trick you might try, before it begins to setup, you might think about taking a small straw and blowing on it in one direction, giving the impression of flowing water?

[denny99]

Yes, Allen. I guess the thinned gel is the way to go, too. I see a talented Australian modeler (Boulder Creek) on YouTube using the airbrush to blow quick shots of air and creating natural movement, I might try something like that. Before committing to the final riverbed, I will try 2-3 different techniques and choose the best resulting one. I will certainly share the results here. Thanks!

[Allen]

👍Looking forward to seeing your results.

[denny99]

I think this is the effect I should aim for. Subtle ripples, with limited movement.

[denny99]

Yes, apparently not too many images on the subject

[Uncle Pete's Basement]

Go search You Tube for the Terminator II chase scenes with Arnold on a bike riding down the LA River. Freeze and analyze the water surfaces.

[denny99]

Ah, I remember that scene Pete! thanks

[denny99]

Anyway, I opted for filling the river gap with a scrap piece of foam and drive the golden spike. I only need to finish trackwork on the staging yard, and I can start operating the layout.

The flex track isn't glued to the foam, so it's all easily removable when I'll be ready to install the final version of the river.




I'm ready to take a summer break, I'll be away for a few weeks. I think I'll bring with me some materials to test the resin and gloss medium / gloss gel while I am on vacation, ready to start over in September.

[denny99]

I finally made some progress on the LA River bridge scene.



After a few tests, I managed to get a "good enough" water effect, and I assembled an RSLaser kit of a 60' girder bridge.










Still in a test-fitting stage, as I need to replace the track with a bridge tie-spacing short section of flextrack, but overall it's a step forward.