#material test

The problem: 

These shoes show exactly what I’m trying to avoid: paint that has cracked and flaked due to the object (mid soles, in this case) flexing, stretching, and compressing over time. If Nike can’t avoid this problem on a $200 pair of shoes, then I certainly don’t expect to solve it with cheap craft items but that won’t stop me from trying! (Image taken from this video; also check out their store for legitimate shoe paint).

The Experiment:

Subjects of today’s experiment include two brands of PVA glue and two brands of paint: Elmer’s Glue All, Mod Podge, DecoArt Americana Paint and M. Graham heavy body Artist Acrylic.There are several important differences in these products:

Mod Podge vs. Elmer’s GlueAll: Mod Podge isn’t just PVA glue; it’s a product meant for decoupage and has additives that enhance its properties when working with paper. It is stronger than standard school glue and will last many years longer without yellowing, cracking, or failing. Elmer’s GlueAll is the grown up version of the classic kids product. According to their site, the main difference is that GlueAll is not washable when fully dried, plus it is stronger. GlueAll is a less specialized option than Mod Podge.

DecoArt Acrylics vs. M. Graham Acrylics: These guys are even more different from one another than the glues. DecoArt paints are affordable, widely available, and popular among crafters because they come in so many colors. It’s easy to walk into any craft store and grab all the hues you need, no mixing required. They are a watery acrylic with a flat, matte finish and are easy to apply. By comparison, M. Graham acrylics are targeted at painters. Buttery thick and highly pigmented, they come in a smaller range of shades because they are meant to be mixed while the artist is painting. Since I used to paint, I am partial to artists acrylics (specifically this brand) but I’ll admit they can be more trouble than they’re worth for cosplay. Artist acrylics tend to be expensive and some of the pigments are toxic (cadmium, anyone?), but high quality sure is nice. We’ll find out if it’s worth the extra $$

Various combinations of these products were applied directly to EVA foam and tested across 5 categories:

Coats to full coverage

How well they performed with masking

Texture

Convex bending

Concave bending

Each glue was combined with each paint, then then the combinations were tested straight and diluted 50% with water. Confused yet? Here are the samples:

Mod Podge + DecoArt

Mod Podge + DecoArt + Water

Mod Podge + Artist Acrylic 

Mod Podge + Artist Acrylic + Water

Elmers + DecoArt

Elmers + DecoArt + Water

Elmers + Artist Acrylic

Elmers + Artist Acrylic + Water

1. Coats to Full Coverage

The paint/glue mixture was applied directly to black EVA foam. I’m sure it would have taken fewer coats if the foam was sealed first, but oh well. Shown here are the Mod Podge samples because I derped up and don’t have good photos of the Elmers. Thankfully both sets of glue looked identical, so these photos are still relevant. From left to right we have: DecoArt, DecoArt + water, Artist Acrylic, and Artist Acrylic + Water.

As you can see, the watered down paints took more coats to achieve the same level of opacity. Each sample has some unique texture although it is not visible from afar. In terms of application, Elmer’s + Paint was easier to mix and apply plus it took fewer coats.  For some reason the Artist Acrylic got kind of chunky when mixed with Mod Podge, but it seemed to brush on acceptably. For the fewest number of coats, I would recommend a 50/50 mix of Artist Acrylics and Elmer’s Glue.

2. Masking

Man, pulling off that tape was so satisfying :P Most samples performed fine, but watered down Mod Podge bled under its masking tape. In this test, Elmer’s was definitely the superior product. Between the paints, DecoArt is more powdery when dry whereas Artist Acrylics are more rubbery. This means DecoArt gives a slightly cleaner result as masks are removed. (btw, those numbers are how many coats were needed to cover the foam).

Here you can see the most offending sample: Mod Podge + DecoArt + Water

DecoArt and Elmers glue had the cleanest result, but just barely. 

3. Texture

The reason I love spray painting so much is that brush strokes drive me nuts when they’re unintentional. Hence my goal was to get the smoothest results possible. I was hoping a foam brush would help, but unfortunately it just left bubbles in my paint job. Elmer’s glue was markedly more smooth than Mod Podge. While highly pigmented Artist Acrylics had better coverage, their thick consistency left brush strokes galore. 

Here you can see the result of undiluted Mod Podge and Artist Acrylic, the thickest mixture of all:

By comparison, check out undiluted DecoArt and Elmer’s glue:

4. Convex Bending

And now for the important part! Each sample was bent past a 90 degree angle several times. This would make any normal paint crack upon expanding and/or crinkle when flattened. Amazingly, every sample performed well except for two: DecoArt combined with Elmer’s glue. Look at diluted Mod Podge and Artist Acrylic bending like a champ:

And here is DecoArt + Elmer’s + Water failing on the first bend:

In the end, I think Artist Acrylic’s rubbery nature helped it bend better.

5. Concave Bending

Unfortunately, all of the samples struggled here. As the foam was folded in half, the paint was compressed into wrinkles that remained even after the piece was flattened. The test revealed three clear factors that contributed to bad wrinkles:

Elmer’s fared worse than Mod Podge

DecoArt is not really a flexible paint, so it had worse results

Diluted paints had much larger wrinkles.

With that in mind, take a look at the sample that had the three worst options: DecoArt + Mod Podge + Water

Yuck! Now look at the result of the best products: Mod Podge and Artist Acrylic: 

Somehow you can hardly see the wrinkling even after bending the piece multiple times.

Final Thoughts