Product Review: Flexbond

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By now you’ve probably heard the announcement that CosplaySupplies.com is now carrying Flexbond, a popular theatrical glue that up until now was difficult to come by in small quantities. After the jump, I’ll be testing and reviewing this product so you can see how it works on foam and Worbla!

I’m no stranger to hijacking theatrical supplies for cosplay purposes; I’ve been using Sculpt Or Coat for years, and I’d heard about Flexbond via discussion on the RPF, though I had not tried it out because at the time it was only available in large quantities. Now it is finally available in smaller bottles, so you don’t have to buy it by the gallon!

So what is Flexbond?

Flexbond is an adhesive and coating agent, sold primarily for theatrical set and prop applications (much like competitor Sculpt or Coat, which I’ve talked about previously). It’s similar in appearance and odor to regular white glue, only it’s much thicker. It works both as a glue and as a coating and smoothing agent for foam or plastic. It dries clear and, unlike many coating agents, remains flexible and does not crack. It is also nontoxic, which is always a plus!

My Test Swatches

I tested Flexbond on both 2mm EVA craft foam and on new, non-thermoformed Worbla (I used flat pieces, since I wanted to test flexibility rather than structural integrity).

First, here’s plain black craft foam with a very thick coating of Flexbond:

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As you can see, when dry it creates a smooth satin finish. Flexbond dries clear, but because it reflects so much more light than the matte foam, the color appears a bit lighter in some conditions. Because the coat was applied thick, there are some brushstrokes visible, and there are also some tiny holes where bubbles were trapped in the glue. (Applying multiple thinner coats would prevent these issues.)

As its name implies, Flexbond is very flexible when dry and will bend, roll, and curve without cracking.

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The only way I could succeed in damaging the finish was to fold the coated side in and crease the foam heavily, which crumpled the foam underneath the Flexbond and caused what appeared to be cracks – but on closer examination, the Flexbond itself was still undamaged; just the foam had creased beneath it.

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Here’s the same surface after a little finger-smoothing. The wrinkles really aren’t visible unless the light is reflecting directly across them.

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To test the coating and smoothing capabilities, I made a variety of test pieces using Flexbond and acrylic paint. First, I painted the thinnest coat possible of Flexbond on a piece of foam. I also watered the Flexbond down (it’s water soluble) and painted a runny form of it over another piece of foam:

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The super-thin coat dried without the satin finish of the thick coat; while it smoothed the surface somewhat, it did not seal the foam completely:

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The watered-down coat, which beaded up and dried in little globules, actually made a neat spotty texture that I think would look good as a form of distressing on some materials:

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Over these pieces, I painted both a thin and a very thick coat of acrylic paint:

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When these were dry, I tried distressing them to see how the paint held up to bending and creasing. While the foam itself creased under the paint, the only damage I was able to inflict in the surface treatment was a tiny chip in the thickest area of paint:

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I also wanted to try painting directly on the foam, so I made a control piece (no Flexbond, just paint), and then separately, mixed equal parts Flexbond and paint and painted that mixture on another piece of foam. (Since the Flexbond is white, it makes the paint look lighter when wet, but it dries the correct color.)

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When dry, I applied the same stress tests to these pieces. There was no significant difference in the performance of the two pieces when folding or creasing, but the Flexbond mixture (the slightly glossier one that appears lighter in color) held up a little better to scratching with a fingernail.

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I also made a simple bracer out of scrap foam to test the product’s performance over multiple layers, and covered it with a thick coat of Flexbond:

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Again, applying a super-thick coat, there are some brushstrokes visible in the finished product:

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I added some light acrylic painting over the Flexbond, just to see how the brushstrokes looked under paint.

Important: Just like white glue, Flexbond remains WATER SOLUBLE after it dries. This is good in that you can continue to adjust or smooth it out after you’ve coated your piece, but it’s bad in that if you don’t put a waterproof topcoat on and your armor/prop/etc. gets wet, it will soften and turn white again.

When I added some surface texture on top of the Flexbond with watered-down acrylic paint, the Flexbond softened and became sticky again wherever I painted:

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However, I left it alone to dry, and it went back to clear and dried just fine. I was able to go back and do some detail painting with more acrylic (not watered down) with no trouble. It remained just as flexible and crack-proof as the smaller pieces.

Finished product (in two lighting conditions):

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The bracer remained very flexible, even with a thick coat of Flexbond; I could not get it to crack at all. Additionally, the Flexbond filled in some of the gaps around the edges of the stacked foam pieces, which looked nice. It would probably do an excellent job sealing the edges of foam core or other porous material, as well.

Coating Worbla

Now, on to the Worbla tests. I used Worbla’s Finest Art (a.k.a. plain old tan original Worbla), which has one smooth side and one textured side. In all tests I applied the Flexbond to the textured side of the plastic. One coat of Flexbond was not enough to completely cover the texture, but I was able to get it fairly smooth with three coats. (If I were being super conscientious about brushstrokes, I might do four lighter coats to really smooth it out, but three heavier coats didn’t look bad.)

I folded and rolled the Worbla pieces to test flexibility. The Worbla itself cracked, but the Flexbond coating never did. This piece had two heavy coats of Flexbond:

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As with the foam, I made a control piece (no Flexbond, just paint) and then several pieces with varying numbers of coats of Flexbond. I applied the same acrylic paint over part of each piece to evaluate the effect of flexing on each surface treatment (spoiler: Flexing had no discernible effect on the surface treatment). Here are the results, for visual comparison:

Paint only:

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One thin coat of Flexbond + paint:

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One thick coat of Flexbond + paint:

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Two thick coats of Flexbond + paint:

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Three thick coats of Flexbond + paint (this produced the smoothest results out of all the combinations I tried):

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Flexbond mixed 50:50 with paint (one coat):

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So to achieve a smooth finish, it took at least two, preferably three, coats of Flexbond under the paint. That finish did look very nice and smooth, but anything less left a bit of the rough surface texture showing through. Also, using thick coats left brushstrokes in the Flexbond that often came through in the paint.

Bonus round: Sintra!

Out of curiosity, I tried painting some Flexbond on Sintra (PVC foam board) to see if it would stick. (PVC is notoriously hard to paint and glue without plastic-specific products). As expected, the water-based Flexbond beaded up on the surface, and peeled off relatively easily when dry. Not really surprising, but worth testing, because SCIENCE!

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Cleanup

Flexbond is water-based, so cleanup is simple with soap and water. Most water-based glues rinse out easily with water, but the Flexbond is thick enough that I actually did have to use some soap on my brushes to get all the glue out of the bristles.

Other Comments

I tried spraying Flexbond using a pump atomizer, to see if I could eliminate the brushstroke issue by spraying it on. It didn’t work; the glue was so thick it clogged the mechanism on the first pump, every time. Thinning it down with water would get it through the atomizer, but by that point it had such a low viscosity it didn’t go on evenly and just made puddles. (But hey, now we know. SCIENCE!)

Conclusions

Pros: I was very impressed with the flexibility of Flexbond (not surprising, as that’s its primary selling point). It has a nice satin finish, and I can see plenty of applications for use on materials like foam or flexible plastics that need to bend. I think it could also be used with sculpting materials or to strengthen papier-mâché projects (didn’t have time to try that for this review, but maybe later!). I also like that it can be mixed with paint or pigments for coating, so painted areas will have the same satin finish as any unpainted coated areas.

Neutral: For pieces that don’t need that kind of flexibility, I’m not sure Flexbond is a significant improvement over other commonly-used smoothing products. While it requires fewer coats than, say, wood glue or Mod Podge, it takes a little more work to even out brushstrokes than it would with a product like Sculpt or Coat or spray-on coatings. However, if you don’t already have a supply of one of those other products on hand, Flexbond is versatile enough to pull double duty (and is less expensive than buying Sculpt or Coat by the gallon).

Cons: I am not crazy about the fact that it remains water soluble after it dries. I would definitely want to topcoat my pieces with a waterproof sealant or paint to keep them from being damaged by moisture, and even then I would probably not feel comfortable doing any sort of water-based photoshoot or wearing them in heavy rain.

Overall: It’s not necessarily the best for every application, but if you want one good all-around coating agent, Flexbond seems like it will work on just about anything (except, of course, PVC). It is the most flexible coating I’ve worked with, and it coats effectively in fewer layers than many other materials. As long as you avoid very wet environments, it should be durable enough for normal con activities and extended wear.


So, there you have it! Hopefully this information is useful to you in researching your cosplay projects and materials. If you have any questions about this review or the products I used, feel free to contact me.


Full disclosure: A small sample of Flexbond was provided to me at no cost by CosplaySupplies.com for me to test and review. However, this is not a sponsored review, and I received no other considerations from the company. This is simply an honest examination of the product I received. I don’t make any money on this stuff. 🙂

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