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Fiberglass & Bondo Guide


Railey98 / Crystal is a young art amateur and enjoys dabbling in digital, acrylic, pastel, clay, junk; anything else that she can use to get her ideas out there. Her favorite way to create is using what she has at her immediate disposal and creating something new out of nick-nack and unused pieces.She also enjoys cooking, baking, swimming, hiking, reading, eating, researching, writing, teaching, lounging, lazing, camping, gaming, and tons of more things ending with -ing.

You can find her lurking around her Deviant Art or her Tumblr. You may also want to check out the cool stuff at her Etsy shop.

Tutorial Introduction:

It has taken me many years to realize not everyone is as excited in the pre-planning stages or as diligent a researcher as me. I spend hours upon hours researching even the tiniest thing, so that by the time I'm ready to actually proceed with whatever I'm planning on I know each and every piece and its like I've already done it a thousand times. I'm fearless when it comes to personal interests, and sink a lot into my work. But most people either don't have A) the patience or B) the time or even C) the skill to know what to be looking for and how to proceed.

In light of this I've taken up writing some guides (with pictures of course!) to help the beginning crafter, cosplayer, or just art enthusiast explore the many means of creating, because starting new things alone can be scary! I know, I've been there myself. So, take my hand and off we go down the fantastic Rabbit Hole that is a Wonderland of creativity!

Using Fiberglass-Epoxy-Resin and Bondo Putty:

I've been requested by CosplayTutorial.com to do a walk-through on this particular skill, and have neglected my task until now. So we'll be starting with something simple; the Gas Mask part for an NCR Ranger from Fall Out New Vegas. This is a yet to be complete costume for me so there is no pictures of a finished product, but we only really need the first few steps. (Please note this isn't a guide how to make the entire mask, its just a spring board guide to start people off right.)

What IS Fiberglass-Epoxy-Resin and Bondo Putty?!

This was a HUGE question that was very difficult for me to answer using research alone, so I'll do a little break down:

Epoxy: "Epoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives." (Wiki)

And now in English: You'll get three items, a paint can filled with a goopy liquid that is the Resin and a little tube with more liquid and this is the Hardener, as well as some silky cloth. If you leave the Resin without a lid it will never harden as it does not react with the addition of Oxygen.

You have to add the hardener to complete the chemical bond between the two. Depending on how much Hardener you add will determine how quickly the Resin will harden, no matter the amount of Resin. The best ratio I found is for every 12 Tbs of Resin, add 3-5 drops of Hardener. This will give you enough time to use the Resin and have it harden before your patience runs out. The cloth will be dipped in your concoction, laid out and the bubbles smoothed and be used as the bones, while the Resin is the muscle. (The pictures will help describe this.) When using the cloth always put it on the INSIDE of your object (if there is one) for added stability (no caving in) and smoothness on the outside.

Bondo Putty:

As with the above you'll get two containers, another paint can filled with a grey putty, and another tube of hardener, this time in red with the consistency of cake icing from a tube. The same science is true for this combo too: air doesn't dry the putty the hardener does. However the formula is a bit more touchy for this one, and will honestly take some trial-and-error from you using it. The idea is to add just enough hardener to make the putty a light, but visibly, pink color. This material hardens faster though, so be careful! When it doubt, add LESS hardener, buying yourself more time to work.

Where can I even find this stuff?!:

Another question I had a hard time figuring out! My answer, Walmart. Though it is evil, it is also a life saver. Wander over to the Auto section and look for the repair items. There you should see many many different cans and tubes all with the brand BONDO. The items you want are:

Fiberglass Repair KIT, as this will have all the materials you need, including the cloth;

Bondo Body Filler, it will have a lid on the can with a tube in it, and that is the Hardener. Buying these will save headaches as they're already put together and are cheaper bundled.

Plusses and Minuses of Using Fiberglass and Bondo:

So before we launch into exactly what to do lets talk about why you should or shouldn't use this method. I just want to give you an idea of what you're in for. If you're totally sold on using this method, more power to you! I love it and would recommend it, but only if its the right tool for the job. There is no need to feel turned way from this method, but please take a good hard look on the below lists and think about if its right for you. If so, proceed!

For starters lets go with the positives: And for balance, the negatives too:
As with any project there are obviously specific materials you'll need, more so when working with harsh chemicals. Be sure to have each item here and your process will go swimmingly!


And Finally you want a VERY well ventilated area to work in while using the liquids. When you sand you'll probably want to work outside where its easy to sweep or wipe up the dust.

What kind of price list am I looking at here?!:

Well with any cosplay it depends on how intense you want to get. For these materials alone: Fiberglass-Repair-Kit is about $10-$13; Bondo Putty is about $8-$10; Brushes $1-$3; Gloves $3-$8; Ear Plugs and Mask $10-$12; It all really depends on what you already have and what you're willing to buy and where you live. Prices do vary, but these should be in the ball park. In comparison to some materials, you're getting a steal!

Still with me? Good! Because now we get to the good part, actually doing what we set out to do! Surprised?


For those actually looking to make an NCR Ranger cosplay you'll need the Pepakura to proceed. It can be found here:
Print, cut out, and glue it all together before proceeding.


Carve out a good hour to work steadily on the Fiberglassing. You need to lay out layers and layers of news paper, or your Disposable Table Cloth to protect the table (or ground) where you're working. THIS IS VERY IMPORTANT!! You will NEVER get either material out of the floor! EVER! You've been warned! Now that your work space is covered well put all the materials out on the table, but don't open them just yet. Be sure to read the instructions very, very thoroughly! Snap on your gloves, pour out your Resin, add your Hardener and get that brush ready!


You don't always NEED to use the cloth to help harden. On the outside of the mask we've just put the Resin Liquid and thought that was strong enough to withstand. This will cut down some weight, but mostly just makes the process quicker because there's no fussing with the Cloth Sheets. Go steady but quickly and try to cover the entire surface with one coat. LET DRY, it should be about a half and hour to an hour depending on the temperature of the drying area.


So using cloth is a pain. The threads are huge and LOVE to pull apart on your sticky gloves. Thus, getting them into smaller spaces can be a challenge, but feel free to shove, stamp and pretty much just squish them wherever you need. It won't hurt anything. Remember, cloth on the inside!


As you can see its pointy, drippy, but holding together. Let this dry, and you can go back to sand and cut the edges you don't want slicing your skin open after its set.


The trick to using this substance is to learn to guage how much hardener you need in ratio to how long it will take you to get it in all the little spots, but for something the size of the mask expect another hour of work. For this section I did a golf ball sized glob of the putty, and about an inch of hardener. It took me maybe a minute or two to spread around and I waited just a few more and the putty was no longer soft enough for my fingers to dent. Beware though, the longer you let it sit the more you have to scrape instead of smooth the putty. Once it hits the crumbly stage just leave it. There's no use trying to spread it anymore.

In some areas though I did a different ratio: a golf ball of putty and only half an inch of hardener bought me another five to eight minutes, perfect for areas where I needed to work it into cracks more.

Fortunately later you have to sand this too so many mistakes can be forgiven then!


The inside of the mask is the perfect example as to an area where I used much less hardener. Because all the pepakura folds go IN (which means the inside of the mask) and make high ridges and deep pockets I needed plenty of time to fill out all the areas and to smooth some of the high points to a slope, so the wearer has the most room to put foam to make it fit perfectly. This is just part of the learning curve, so don't worry too much, take it slow and you'll do well.


So it can be a challenge to get the bondo pretty smooth, and you can see here that even after sanding, so take your time! The smoother you get in the applying stages the easier it is to sand later and get a nice finish! No Freddy Kruger skin look… Because I rushed a bit I had to apply another coat of a lighter clay to make it look nice. Also in tighter areas I used a basic, stone dremmel bit to eat away at the bondo and did some light hand sanding in areas as well.


From here the rest is up to you! This is honestly as far as I've gotten with my ever scattered hobbies all pushing each other out of the way to be practiced, and I look forward to someone else picking up where I left off!


I sincerely hope this helped someone! As a costumer you have to remember that nothing will be 100% smooth, crisp or perfect because we live in the real world. The little dings and imperfections make our work real and not part of a cartoon, story or imaginative world. The little bits of you that you add to your works make them truly unique so be fearless and explore whatever it is you feel like! Jumping right into the waters can be so frightful sometimes, but I promise that while there could be sharks the reef full of beautiful fish is worth the risk of a few pointed noses.

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