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How to fix seams on foam armor – tutorial by Germia

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How to fix seams on foam armor – tutorial by Germia
Example of an unclean edge

Seams are always a problematic spot on every foam armor. If you want to look absolutelly flawless in your armored cosplay or impress the judges at cosplay contest, you have to make your seams invisible!

And I’ll try to show you today some ways how to achieve the clean „seamless“ look and also how to fix different errors in your armor.


First step you have to take to make your seams invisible is to prevent them from opening in first place. And how to make it?


The first step is to have your edges clean, well cut and well aligned, so they’re not suffering under a stress and they sit stable in their position. Sharpen your knife regularly to achieve the best clean edges.


Second step is to use a good quality contact cement, I’m using contact cement Extreme from Pattex in tubes, sometime the contact cement is called barge.

hotglue on an edge – too much volume
to make a seamless connection

And the gluing process should be like this:

Put a small film of glue on both glued surfaces and let it dry till it’s tacky or till it looks dry. If you want to be supersure, put another thin layer of glue on both surfaces and let dry – this is done because sometimes the foam absorbes some glue inside and the surface is not glued enough. When it ‚s dry push the surface against each other. If you done those steps well, the connection should be very very strong. You can test your gluing skill on some scrap foam and then try to tear it. The foam should tear anywhere else but in the glued connection and then you did your job well. Also well glued connection does not open when forming the shape of the foam armor or heatsealing it.

DO NOT USE HOTGLUE – Hotglue is a good glue for gluing foam pieces, but it has disadvantages:

1 ) Hotglue has a volume

– it makes space between glued surfaces, so use it only for gluing pieces of foam in layers (on on each other), not next to each other and do not use a ton of it, since it can deform the surface of your foam.

2) Hotglue cannot be re-glued like contact cement

From left to right:
1) clean seams, contact cement connection – flawless
2) bad cut seams -> contact cement cannot connect it properly
3) hotglue connection – too much volume -> big uneven seam

– if you put hotglue on your armor, it stays there forever, you can’t scrape it down, you can jjust reheat it and glue again, but the glue stays! Contact cement can be dissolved with color thinner – for me works Thinner S 6005, but it depends on your local supply. If you want to glue again surfaces, where you’ve used color thinner before, you have to let them completely dry before gluing them again.

3) Hotglue seams look messy
– since hotglue has a volume, you can never do good seams with hotglue.

You can watch a tutorial by EvilTedSmith on youtube:


If you’ve watched the tutorial by Evil Ted, you see him fixing opened connections or uneven places in the foam by using Kwik Seal.

Kwik seal is a kind of a silicone made for sealing cracks in bathrooms. But we don’t have Kwik Seal in Czech Republic, so there are some alternatives like silicone Pattex for bathrooms.

It really works well for fixing seams in armor, BUT I experienced some colors are not very keen to adhere on the silicone surface and since that time I’m not using it and I’m not recommending it anymore, but if your colors work well with kwikseal, you can go for it.


When I got my hands on foam clay for the first time, it seemed like it is a wondermaterial for , but after trying some stuff with it, I’ve found out it’s use isn’t as unviersal as I thought. It is very good for making things like spikes, ornamental stuff, but not for using it alone for projects, it is very tacky when working with it and it dries rather fast from workable tackyness and very slow to finished hardness (especially bigger pieces).

But I’ve found this material to be very useful as a supplement material to normal foam in sheets, especially for fixing errors and seams in the foam pieces.

Sometimes it happens, that your seam opens or that you touch a part of your cosplay with dremel accidentally, or that you want to smooth out connection of different foam pieces.

Foam clay is perfect for that – it fills out gaps, behaves like foam when dried and in small amounts dries superfast.

TIP: Foam clay is supertacky, so wet your fingers in water when working with it or use some tools for smoothing.

Fixing seams with foam clay and sanding
UP: before
DOWN: after


If you work with high quality foam, that doesn’t make munches when you dremel it, you can use also your dremmel to better up your seams, but be really careful with it. You can also use sanding papers instead and use them from rougher to smoother till you’re satisfied.

And that’s it! I hope this article will be useful for someone and if yes, you can follow my work on cosplay (and other stuff) on my FACEBOOK PAGE or TWITTER or INSTAGRAM

And if you like this stuff I do, you can support my work by donating on my PATREON, because their donations made this tutorial possible.



Published: 18.02.19 12:48, Pacific Standard Time

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