EVA Foam is an awesome crafting material, especially for cosplayers and prop makers. It is easy to work with and you only need a handful of inexpensive tools to be able to create great-looking props and costumes. There is, however, one little problem, that a lot of crafters run into. And that is fixing uneven parts, gaps, and seams in their EVA Foam project. After reading this article you will know exactly how to fix even the biggest gaps and how to smooth the ugliest seams with ease.
So how do you fill gaps in EVA Foam? In short, there are several methods, that you can use to fix ugly seams and gaps in EVA Foam. The two easiest methods are using Kwik Seal to fill in gaps and seams and then smoothing the surface of the Kwik Seal with a little water and your finger. The other method is using Foam Clay to fill the gaps and sanding the clay down to make the surface smooth.
Filling Gaps in EVA Foam With Kwik Seal
This is probably the best-known method for filling gaps and fixing seams in EVA Foam and it makes sealing the foam afterward quite easy too.
Kwik Seal can be found in any hardware store. It is a multi-purpose adhesive caulk usually used in the kitchen or bathrooms.
Most crafters and Prop makers, who work with EVA Foam, use Kwik Seal to fix gaps and seams.
To fix seams with Kwik Seal simply apply Kwik Seal to the gap or the seam, that you want to fill. Then use some water and your finger (I would recommend wearing disposable gloves for this part) and smooth the Kwik seal with your finger and some water.
The result will be very smooth and no seams or gaps will be visible after you are done. Let the Kwik Seal dry for a few hours until it is solid.
If the result is not smooth enough then you can slightly sand Kwik seal with a fine grid sanding paper to give it an even smoother finish. But most of the time this won´t be necessary if you smoothed Kwik Seal well enough when you applied it.
There is a great video from Punished Props Akademie where you can see how they fixed the seams of a helmet with Kwik Seal.
Filling Gaps in EVA Foam With Foam Clay
This method is personally my favorite method but only because I love Foam Clay.
It is a little more expensive than using Kwik Seal but you have a lot more possibilities with this method.
Foam Clay is basically exactly what it says what it is. It is foam, that can be shaped and formed freely just like clay. It will dry slowly and once it is dried it is exactly like regular EVA Foam.
You can sand it, shape it, and glue it just like EVA Foam.
You can find Foam Clay right here on Amazon.
The link above is an affiliate link. If you want to support me, then you can use the link to buy your materials. It doesn´t cost you anything extra and I will get a small commission for every sale. I only recommend tools and materials, that I personally use and like.
I usually use it to form organic forms where sheets of Foam is kind of hard to get into the right form, or you have to sand a lot in order to get it to look like an organic form.
But I also use it to fix gaps and seams. Simply use a little bit of water and wet the surface around and in the gap. Then take a little bit of the Foam Clay and apply it to the surface. The water will slightly dissolve the foam clay and make it stick to the surface of the EVA Foam.
Then use some water and your finger (this time you won´t need disposable gloves) to smooth the surface of the foam. Then let it dry for a few hours and once it is dry you can sand it if you see some uneven parts or if you want to make the surface smoother.
Can You Use Bondo on EVA Foam?
Bondo is a body filler that is mainly used in the automotive industry. It is a two-part mixture, that you can shape any way you like. It is quite cheap and easy to come by.
So can you use Bondo on EVA Foam? In short, yes you can. You only have to lightly sand the area of the EVA Foam where you want to apply Bondo so that the Bondo has something to grip on to. Then Mix your hardener with the right amount of Bondo and simply apply it to the surface of your EVA foam. Once the Bondo has dried you can sand it to give it a smooth finish.
Bondo is available in almost all hardware stores or car repair stores. It is quite cheap and easy to use.
You have to mix the hardener with the right amount of Bondo before you can apply any Bondo to your Project.
Make sure, that the surface, that you want to apply Bondo to is rough enough for the Bondo to stick to. So if you want to apply Bondo to EVA Foam, then lightly sand the area, where you want to apply it to.
Mix the hardener and the Bondo well and then apply it to the EVA Foam. You can use Bondo to fill in seams, cracks, or gaps.
Roughly apply the Bondo to fill in the gap or seam, that you want to fix. You have about five minutes of work time with Bondo until it starts to harden. It depends on how much hardener you mixed in.
Once the Bondo becomes kind of Crumbly the work time is over and you should stop moving or shaping it. Wait for a couple of hours until it is completely dry.
Then use rough grit sandpaper to roughly shape the Bondo and to get rid of blobs or other uneven parts. Then move on to finer grit sandpaper like an 800 grit to smooth the surface of the Bondo. If you want a very smooth surface, then you can even use a 100 grit and wet sand it. But most of the time, I find, that Bondo is smooth enough once I sanded it with an 800 grit.
Bondo can be sealed with Plasti Dip or White Crafts Glue and it can be painted without any problems. So it is an awesome medium to use for Prop making and Foam crafting.
I personally prefer using Foam Clay or Kwik Seal over Bondo for fixing seams and gaps because it is faster and easier to use these methods compared to Bondo but there are a lot of other projects, where Bondo is better. For example, if I have to fix a big surface, then Bondo is better because it is so much cheaper and it is easier to mix a big batch of Bondo than using a lot of Foam Clay or Kwik Seal.
I also use Bondo if I want the surface of my Foam to be rigid. So for crafting armor, I like to put a small layer of Bondo on top of the armor to make it rigid. This gives an extra layer of detail when people touch the armor.
But that is entirely up to you.
Hi, I am a passionate maker and professional prop maker for the entertainment industry. I use my woodworking, programming, electronics, and illustration know-how to create interactive props and puzzles for Escape Games and marketing agencies. And I share my knowledge and my experience on this blog with you so that you can become a maker yourself.