Sealing: Elmers Glue-All, Modge Podge, Plasti-Dip... or all 3?

[ShadowNinja1012]

Hello,

I have two different queries: first, I have been working on a Daedric sword using EVA foam as the base. I've gotten to the point where I'd like to begin painting it. I used a few coats of spray plasti-dip followed by a coat of automotive filler primer (which I had used before on resin/bondo pieces) but the end result was that the primer cracked as seen in the picture. How would I go about fixing this? Try to cover it in more plasti-dip or more primer? Should I use a different type of primer for EVA foam? I'd also like to point out that I didn't try to bend/flex the sword at all, that is just how the primer dried, so maybe it shrank in the process.


My second question is for my upcoming project. I am in the process of making a steel chestplate out of EVA foam. When I go to seal it, what should I use: Elmers Glue-All, Modge Podge, Plasti-Dip, or all 3? I've read about different techniques such as the one mentioned by laellee in this thread:

I've built quite a bit, and I settled on this process for EVA:

1- Finish building the piece
2- Float the heat gun over all of the surfaces to tighten and set the surface. Don't go crazy or hot-glued seams will separate.
3- I look over the pieces for pinholes or openings in seams, and fill these with paintable silicone caulking. I just use my finger to smear it in, then let it dry.
4-Mix PVA glue and water at about a 4:1 ratio, I try to get it a little thinner than house paint. I paint on my coats as thin as possible. I check the pieces a couple of times in the first half hour, brushing out any runs and pooled areas in corners and joints; if you don't get them out when they're wet, they're much harder to clean up later. You can get away with 2 coats, but 3 or more gives you a much better finish.
5- I then follow up with a couple of coats of Plastidip (spray). Some people paint right over the PVA coats, with good results. I noticed on my pieces, especially flexible sections like the abs and gloves, that repeated flexing created cracking and fissuring in the PVA. A couple of coats of Plastidip seals the PVA, hiding most all of my cracking. It also gives the pieces a uniform color over the PVA, so I can catch any extra imperfections that I didn't see in the PVA coat.

Anyways, that's what I do, and it works well. Some people don't like the expense of the Plastidip, but I think it's well worth the extra spending.

- Just to add, in regards to the PVA and Plastidip: EVA foam sucks up both glue and Plasti. You can seal pieces in just Plastidip, but you'll have to use quite a bit more than if you had applied a PVA sealer first.

This definitely seems like a great technique but just out of curiosity: what have other people used? Is Elmer's glue-all (like this) considered PVA glue or do I need a special PVA glue such as the stuff used for bookbinding? Should Modge Podge have some sort of role in the sealing process?

Thank you for your input!

 

[dkasai]

I'm wondering the same thing. I just tried my first project using 3:1 PVA (wood glue) mixture, 3 coats with sanding in between which was recommended on another post "The definitive guide to sealing foam..." It didn't work at all for me. Cracked like an egg and now I'm trying to figure out how to fix it. Sounds like PlastiDip might be better but I've heard it looks muddy and imperfect. Just FYI.

 

[MWiggs]

I did extensive research on just about every coating/sealing process you can think of, and much like you, dkasai, PVA just cracked liked crazy for me no matter how much I watered it down or how thick I put it on. Mod-podge was a little better but still wasn't able to take an impact without cracking. I even tried using just paint directly on the EVA foam but even that had a hard time. I used straight Plastidip in the end and after 3 coats of primer and some light sanding with 600 grit the surface came out more smooth than I could have hoped for. Still won't be smooth as glass, but unless you're polishing the surface to a high gloss that shouldn't be a problem. What works for one may not work for all. Just my 2 cents. Good luck!

 

[Shiroppi]

here's my personal experience with sealing foam. one thing for sure is i NEVER use primer on any of them after sealing. i never get any cracks with plastidip, latex or latex glue.

Plastidip : directly to foam , 6 layers. follow the instruction . its fine. dont like the texture.

PVA : i hate PVA.. it runs everywhere . Elmer glue is PVA btw.

Latex : like PunishedProps and EvilTed, i like using thinned latex. it's smooth and flexible. minimum 4 layers. catch is, u need a compressor gun and critter gun to use it. quite expensive in my country despite this country make them.

Latex glue : 3 times more exp than PVA but i use this almost all the time. i didnt thin it. apply directly to foam for 3 layers. the smoother u apply, smoother the finish. dries fast and didnt drip as much PVA.

Epsilon : this is to go for more rigid feel. its a epoxy resin that can be applied directly to foam. I used this for some of my project that doesnt need to be flexible. also use this to coat polystyrene ball for my BB-8 . you can apply bondo and then primer it like any rigid methods.

i have friends and know some fabricator from thailand / indonesia that they use wood glue. im not sure if they mix with anything else tho.

 

[AndyTheFirefly]

To seal foam I heat gun the foam to seal it and then apply several layers of plasti-dip, enough that it looks like a paint job, then you can paint it.

The problem that occurred with your project was probably that you used bondo AFTER plasti dipping. Bondo isn't the best becuase it is rigid and the foam is flexible, so when the foam flexes, the bondo can crack. To seal cracks you need to use a flexible paintable caulking. I used Kwik Seal by DAP. Use caulking first to seal the imperfections, THEN plasti-dip and paint.

You can put glue on first and then plasti-dip, but from what I have heard the best is plasti-dip alone. Although, if you wish to cut down costs, that is an option. I have not tried this.

 

[GatorBubs313]

I just accidentally came across this thread while researching pva glue and figured I’d throw my two cents in since I have some experience sealing foam.. craft foam and styrofoam… and even spray foam for some other projects… anyway I found that using plastic wood… (the wood filler) works amazing for bonding and smoothing and sealing the foam of any kind… and the best part of all it’s stainable, paintable and sandable in a fairly quick amount of time. Doesn’t need a crazy amount either… I usually just apply it with my fingers / hands for the best smooth surface that requires less sanding in the end. Hope this helps anyone in this thread or that stumbles across it like I did.