FOAM Builders! New hardening technique - Alternative to Plasti-dip and PVA!

I have been testing for the last three months, trying to find an alternative to the PVA and Plasti-dip method. I am confident enough to say, "I have found the truth!"

First, a bit of backstory!

What is the purpose of PVA?

PVA is used to seal the EVA to allow it to accept external paint. It is sand-able, but sometimes has a tendency to "roll" or "ball" up.

Issues: PVA does seal the EVA, but at a pretty high cost. It tends to crack very easily, and will reconstitute with the most minor amount of moisture. Sometimes it does not adhere to areas of EVA, avoiding patches with voracity. It also tends to kill details by pooling in crevices, detail lines, and corners. This would be okay in some circumstances, but it also tends to be inconsistent in doing this task, often creating air bubbles that are extremely difficult to fill with another coat, or seeping into cracks, leaving what I refer to as "Morse code" areas that have glue, and then no glue.

So, what is the purpose of Plasti-dip then?

Plasti-dip is used to coat over the PVA to give it a paintable surface, and also provides a bit of give in the case that the PVA cracks under light pressure.

Issues: Plasti-dip is EXPENSIVE or not available in some areas! It also is really temperamental with weather conditions when applying. In addition, it is yet another heavy coat that tends to fill in details even more. One more thing is that it is not sandable.

With these cons adding up quickly, I set out to find an alternative.

In order for it to meet my standards for an approved method, it must:

- Be rigid, but also a little flexible, enough to the point that that it does not crack when bumped or bent lightly, but has that "click" sound as a pose to the "thump" sound with flicked with a finger.
- Resemble "hard" armor appearance
- Show full detail and not pool up at all
- Coat the entire surface evenly and consistently
- Be sand-able at all stages (minus the final paint stage)
- Fill small imperfections.
- Be cost effective and a product that is easily obtained!
- NOT AFFECT THE SHAPE OR HARM THE EVA or SUPERGLUE

Now, the process. (Please note - I have not tested this with hot glue yet. This was performed on blank pieces of EVA, and some that had been super-glued together)

Step 1 - Prepare your surface! Make sure that all EVA has been heat "treated" or formed. To heat treat, simply use a heat gun to close the surface cells (this should be performed during construction and not necessarily at the end of your project as it has a tendency to slightly reduce the size of the foam). Be sure it is clean of foreign materials and that all "fuzzies" (the hairy pieces of EVA left from bad cuts or sanding). These can generally be taken care of by brushing on SuperGlue and then sanding it down when dry.

Step 2 - Apply a generous coat of CORN STARCH. Massage it into the EVA, making sure that all surfaces to be treated have this done. Wipe off ALL excess. It will go back to the way it looked before, but if you look really close, you will see that it has filled the smallest of holes .

Step 3 - Using a SPRAY can of Satin Polyurethane - apply a generous first coat of this to the surface to be treated. FOLLOW THE DIRECTIONS ON THE LABEL and I stress to use in a well ventilated area. DO NOT BE ALARMED, IT WILL SOAK INTO THE EVA! Photo below for reference of what I used. FYI, I paid $6.50 for this can at my local overpriced hardware store.



Allow to dry between coats, but not longer than 1 hour. I set mine in the sun for about 15 minutes between coats.

Apply about 4 coats, each one getting lighter as you progress. Stop just after the surface stays wet looking.

LET CURE for at least 12 hours! If not, the next stage will go horribly wrong. At this point, you can sand down any larger imperfections there may be... you can even add a thin coat of Bondo (not recommended due to higher probability of cracking).

At this point, the surface should be somewhat hard, but still a bit flexible (simply the properties of polyurethane). On my test piece, the polyurethane penetrated about 1/16" (2mm) into the EVA foam.

Step 4 - Wash with a mild dish soap and dry thoroughly. Allow all areas to air dry and make certain no water remains.

Step 5 - Using a wet/dry sandable auto primer, apply 2-3 coats. Wet sand in-between coats and allow to dry before applying the next coat. Allow to cure for no less than 4 hours on your last coat. Below is a photo of what I used. Approximate cost was $4.



Step 6 - Once the surface is smooth and acceptable, wash one last time with a mild detergent and dry with a no-nap cloth. Allow to fully dry.

Step 7 - Apply the paint of your choosing, following the directions on the label.

Here is a photo of a test piece I did today. On the far right, I have finished the 4th coat of the polyurethane. In the middle, I had applied primer and then paint. On the left most area, I had performed all of the steps listed above.



Please feel free to post questions or comments!!!

Thanks for looking and I hope this helps!

I'll have to give this a go! I've been trying to find a better sealing solution as I've grown tired of plasti-dip. I'm wondering where everyone is trying to get their Plasti-dip from. At my local Walmart they are only ~$5.50 for a 10 oz spray can yet everyone seems to only find them at ~$13.00 a can. Maybe it's just the area I live in? Anyways, keep your knowledge flowing with these threads. They are VERY helpful.

You can also use gesso to seal the foam but it is far inferior to plastidip. So if this method is better then plastidip then that's awesome

where I am in Canada Plastidip is 19.99-24.99 a can, so this should be good for me.

One of the things I had in mind while doing this research was the people in other countries that either could not get Plasti-dip, or afford the extraordinary price of it there.

Just as a note. My wife decided to go bonkers on the test piece. She bent it completely in half, then let it relax. There was no cracking at all, and the only sign that she had done it was a couple of wrinkles that healed almost completely... especially when she added heat to it.

Do you think this will seal polystyrene? i am working on an AR with it and need something to seal it with...

I am err on the side of caution and say "no". Only because the Acetone and other petroleum products it contains would probably eat away at it. I have a piece lying around that I may do a test on if I get a chance to though.

Thanks, it seems like general sprays are a no-no because of the solvents used to carry the pigments etc. I guess plasti dip

Very cool stuff. It sounds like it has excellent physical properties. How does it hold up after 2 weeks of curing? I have tried many things like this over the last year, and at first they seem good, but after two weeks of curing, they are no longer as flexible.

I have not gotten that far in as this specific process has only been in effect for a very short time, but I can't see a downside to it curing even harder. I am kind of under the impression that was what most are looking to accomplish (I know I am )

Once again you are ruling this game. I'll be trying that method on my next foam project. Thanks evakura.

Alternatively...

http://www.405th.com/showthread.php...ef-Going-into-Cryostasis!?p=680031#post680031

...which allows you to do this...

http://www.405th.com/showthread.php...ef-Going-into-Cryostasis!?p=677042#post677042
http://www.405th.com/showthread.php...ef-Going-into-Cryostasis!?p=679732#post679732

Both methods are very interesting I will need to try both of them.

Carpathia, did you only use one layer alone on the armour, or did you put anything else on? You should totally make a guide for the process you did.

Has anyone tried EVAKura's Method with Hot Glue? If not I can test it sometime next week.

Bulmung4, I am trying this method out as we speak on my H4 bicep, which I used hot glue on. So far, everything seems to be going very smoothly and I don't see any degradation to the hot glue at all. FYI, I only use high temp hot glue, but don't think there would be any difference with the multi-temp or low temp glues.

Do spray cans of polyethylene exist?
Might be able to make your pieces more durable with it.


Now I'm all worried about cracking the armor I make....



Why not add the layers of polyurethane, wait for it to finish settling, then remove the foam from the backside and then increase the thickness of the interiors of the parts with more polyurethane?
You'd basically be making a thin mold of all your parts, and then adding a permanent cast on the inside. Then you can sand down the mold however you wish in order to bring back some of the finer details.
I'm just theorizing here, don't mind me.


Also, how well does craft foam (foamies) survive up to your method / could you test it?
I know people often accentuate their parts of eva foam with the craft foam, so I figured I'd ask.

This is genius! Thanks so much for sharing, I think you may have revolutionized foam sealing

WandererTJ said:

Why not add the layers of polyurethane, wait for it to finish settling, then remove the foam from the backside and then increase the thickness of the interiors of the parts with more polyurethane?
You'd basically be making a thin mold of all your parts, and then adding a permanent cast on the inside. Then you can sand down the mold however you wish in order to bring back some of the finer details.
I'm just theorizing here, don't mind me.

Also, how well does craft foam (foamies) survive up to your method / could you test it?
I know people often accentuate their parts of eva foam with the craft foam, so I figured I'd ask.

Click to expand...

The reason why that can't be done with this method is because the polyurethane soaks into the EVA, becoming "one" with it. Also, after 5 days of curing, it is still a bit flexible.

Both the H4 MC shoulders and bicep that I performed this method on had a decent amount of Foamies on them, and they accepted the polyurethane the same as the EVA mats did

Apothacary said:

This is genius! Thanks so much for sharing, I think you may have revolutionized foam sealing

Click to expand...

My pleasure! I must admit that it was for selfish reasons I did it.... I can't stand the cons to both PVA and Plasti-dip... but I figured at least I could share!

Man, Now that I think of it; I wonder how much better the Binary Rifle would have come out?!?!

im sold on this...gonna go to lowes or home depot to look for them

There is just one small issue with this method...For me, it is actually way more expensive to do this than to go with plasti dip. See, here in Germany you will not find anything that is 400 ml, and in an aerosol can for under 10 euro. There is just no way it can happen. That's about 15 dollars per can. For a whole suit, and 4 layers, I would need around 10 cans (yeah, I am around 6 ft. 2, I built the mark vii suit) and this would cost a huge amount. It would cost around 150 dollars just for the sealing, not counting primer and paint, and that is way more than I can afford. Even though plasti dip here is around 25 dollars a can (converted from euro) I don't need so many layers; just enough to go over everything, so that the paint doesn't crack when the foam piece is flexed. Also, I don't really know what pva you use. Usually, pva dries like a type of rubber. It is pretty flexible, so I don't see why it would crack. I have access to a ton of pva, so that is free, and I only have to get around 3-4 cans of plasti-dip, which is considerably cheaper. I don't have to prime either; I an just paint over. It's a lot easier like this, I think. Many people have gotten different results with pva, so it really depends on how it is used. Take a look at what James from Xrobots did. He used the "traditional" method to seal the foam, and his suit is one of the most perfect I have seen around. What are your thoughts on this? I also wanted to use PVA, because it would fill in the imperfections, like scratches or pokes in the foam (yeah, I used eva foam camping mats, because, again, in Germany the floor mats cost like 30 dollars for a 4 pack. The camping mats costed 10 dollars for one, which is considerably less. The mats are a lot easier to puncture and scratch though, so I want to get a good coat of pva on to fill in any imperfections, and to protect the foam from further damage) Man, why is everything so expensive here?