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Basic Fiberglass Tutorial


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This tutorial is for the basic technique of laying up fiberglass mat or cloth in a mold.

 

It's going to take me a while to type up a full tutorial and add pictures, but here's a start. I'll add more to this each time I get a chance.

 

 

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First, be aware that working with fiberglass is messy and potentially dangerous. The resin is sticky, and the fumes are not good for your health. The fiberglass itself is a skin irritant. Protect yourself by wearing a respirator, long sleeves, and gloves... and protect your work surface by covering it with plastic or newspaper. Don't let the precautions scare you away, though. As long as you take proper care of yourself and your workspace while you handle the fiberglass and resin, these materials will help you create high quality and amazingly durable costume pieces.

 

 

Materials Needed:

 

 

- Polyester Fiberglass Resin (It's more cost effective to get it by the gallon.)

- Fiberglass Mat or Cloth (For small projects, I prefer the cloth. It takes curves and is easier to apply.)

- Resin Catalyst

- Respirator (Use a high quality respirator, NOT a dust mask!)

- Eye Protectors (Goggles, or the glasses type. Protect your eyes from resin splashes.)

- Disposable Paint Brushes (Home Depot sells affordable 15-pack bags of 2" chip brushes!)

- Pre-made Gel Coat, or Talc so that you can make your own Gel Coat. (Baby powder will do.)

- Plastic cups (I prefer the low, wide cups so that I can dip the brush in easily.)

- Measuring cup

- Sharpie

- Stir sticks (Plastic spoons work great!)

- Drip Sheet (I get a roll of plastic, and cut pieces off as needed. Newspaper works, also.)

- Long sleeved shirt

- Disposable Gloves (Get a whole box and keep it handy. Change gloves when they get sticky.)

- Acetone (If you want to have it handy for cleaning brushes or resin spills. I never use it.)

 

 

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- Start by making sure that your mold is clean, and put down a sheet of plastic or some newspaper over your work area. Set out the materials you are going to use.

 

 

- Apply release to the mold. If the mold is made of silicone the fiberglass won't stick, but it's still a good idea to give the mold a light spray of release to lengthen the life of the mold. Molds made with other materials will need to be sealed and coated with a high quality release. Several light coats of PVA are a good idea. It's always wise to do a test on some scrap material before you begin working with fiberglass, to make sure that everything will release as needed, and so that you will know how to use the materials before you risk damaging any sculptures or molds you have done.

 

- Put on your respirator, goggles and gloves before you begin handling polyester resin. You should never breathe the fumes.

 

- It's a good idea to make a stack of pre-labeled disposable mixing cups before you begin a project. Determine how much resin you want to mix each time (I typically mix 4 ounces), and measure that much water into a cup. Use the Sharpie to mark the water line, and then pour the water into another cup. Mark the water line again, and so on until you have a stack of pre-labeled cups. Dry them well.

 

- If you are going to use a purchased gel coat, you will simply mix a batch according to the instructions on the can. Measure out the resin, and then add drops of the catalyst. Mix well. You will need just enough to give your mold a single thick coating of resin.

 

- If you do not have a pre-made gel coat, you will need to make your own. Begin by pouring the desired amount of resin into a cup. Again, you will need just enough to give your mold a single thick coating of resin. Pour in talcum powder, mixing it thoroughly until your resin begins to thicken and no clumps remain. Since talc is very lightweight and not tightly packed, I usually pour in as much powder as the amount of resin I used. Then, add catalyst according to the directions on the label, and mix well once again. (The brand of resin I use typically requires from 10 to 14 drops of catalyst per ounce of resin, depending on the weather.)

 

 

Note: Fiberglass resin is very sensitive to temperature. If the weather is hot, the resin will cure VERY fast, often while it is still in your mixing cup. In this case, you can reduce the amount of catalyst you use by a few drops to help slow down the cure time. If the weather is cold, the resin will cure very slowly. You can speed up the process by adding a few extra drops of catalyst... but don't add too much. Working in cold temperatures with too much catalyst will create fiberglass that is very brittle.

 

- Use a disposable chip brush to apply the gel coat to your mold. Make sure to cover every surface as evenly as you can, and make sure you do not leave any air bubbles trapped in the resin. If the gel coat pools at the bottom of the mold, you can brush it back to the top again. Continue doing so if you need to until the gel coat begins to set. Once it starts to thicken into a gel, do NOT touch it anymore! You will damage the front surface of your casting, and you won't be able to see it until you're done with the project.

 

- While you are waiting for the gel coat to harden, clean up the area if you need to and prepare your fiberglass. I usually throw away my brush instead of trying to clean it.

 

- If you are going to use woven fiberglass cloth, cut it with scissors into pieces that are a good size for your project. If you use fiberglass mat, tear it apart with your fingers so the fibers will frayed. I usually cut a variety of sizes and shapes, depending on the size of the project I am working on and the shapes of the pattern that the fiberglass will need to fit into. I prefer to keep the pieces no larger than 4 inches square, because it's hard to get air bubbles out from under larger pieces. Rectangles that are 2-3 inches wide and as long as necessary are often the easiest to work with in my opinion.

 

- After the gel coat has cured enough that it is stiff, but is still just tacky enough that touching it can leave a slight fingerprint, it is time to start applying your cloth or mat. You don't want to start too soon, because the pattern of the cloth or mat will press through the gel coat and show up on the front surface if the gel coat is still too soft.

 

- Mix another batch of resin. The amount you mix will be dependent on the size of the project. For smaller projects, I typically mix 2 or 4 ounces of resin at a time. Even for large projects, I rarely mix more than 6 or 8 ounces. I'm a meticulous worker, and I don't like being forced to hurry because I'm racing the cure time of a big batch of resin.

 

- Paint a layer of resin onto the back of the gel coat. Lay a piece of fiberglass on the wet resin, and then use your brush to press it into the resin. Use the brush in a stippling motion, repeatedly pressing down the fiberglass so that all of the air under it is forced out and the fibers lay close against the gel coat. As the fiberglass soaks up the resin it will turn transparent. Any places that remain white will need to have a bit more resin brushed on. Air bubbles should be forced out from under the fiberglass with your brush.

 

- Continue adding more pieces of fiberglass using the same technique, extending the pieces out past the edges of your mold. (You can cut off the excess with a dremel tool after the resin cures.) Press each piece of fiberglass onto an area already wet with resin, and then add a bit more resin on top. Overlap each piece of fiberglass, crisscrossing them for added strength. The thickness of the fiberglass will depend on the strength that will be needed for your finished piece. For costume construction, I typically use about five to seven layers of fiberglass. It is very strong, but still lightweight and thin. If your gloves get sticky while you are working, change them.

 

- If you run out of resin, mix another batch. You will need to throw away your plastic cup and use another cup for every new batch of resin, but you can typically continue to use the same brush until the resin in it begins to cure. Do NOT use the same cup over and over again... the resin will eventually melt through the plastic, and you'll end up with a puddle of resin spreading across your work table!

 

- When you have finished giving your mold an even thickness of fiberglass all the way around, set it aside to cure. I typically wait until the resin is completely cured, just to be safe... but I know that some people prefer to pop the piece out of the mold while it is still slightly flexible, which makes it easier to remove. It's a matter of personal preference, and also depends on if the fiberglass might get locked in the mold if you wait until it is no longer flexible.

 

- Hold the fiberglass piece up to a light and check for thin spots. If you see any, it is a simple task to mix a bit more resin and add another layer or two of fiberglass.

 

- Finish the piece by cleaning up the edges. Dremels work best for this. Wear your respirator when grinding or cutting fiberglass. The resin fumes aren't really a problem anymore, but the particles you'll be sending into the air can't be good for you to breathe!

 

- Sand down any problem spots. If you want a very glossy front surface, the best results will be achieved by wet-sanding with 600 or 800 grit sandpaper.

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If there are any problems with the front surface of a fiberglass costume piece... such as damaged spots in the gel coat, or if the pattern of the cloth shows through, there is a way to fix it. Set the piece up on a support that keeps it from touching the tabletop. Then, mix up a batch of resin, add some talc to thicken it a bit, and then paint it on the front surface of your costume piece. The resin will still be a bit runny, so it will fill in any marks left by the brush, leaving a glassy smooth surface. It will also drip off the edges of the piece, but there's not much you can do about that. Let it drip, and let the resin that remains have time to cure. When it's done just cut off the drips, and you'll have a much better work surface for the front.

 

 

Pam :-)

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I am attempting a breastplate and shoulder bells for a Rahm Kota (yeah I know he's not Imperial :roll: ) costume. I'm going to try fiberglass with either polyester or vinyl resin. (Which of those makes a lighter cast, does anybody know?) I'm struggling with just how to attach these pieces to the wearer as there is no backplate to the armor set.

 

I wondered if anybody has tried to bond velcro loop material right into the sticky resin, so that when it sets up it has the soft strips all around the inside edges of the plate. That would make attaching straps (elastic or rigid) a lot easier. Would the velcro material soak up enough resin to bond it to the piece, or would it pull right off when the resin was cured? Any ideas?

 

Also, what would a 16" x 14" x 1/4" fiberglass breastplate weigh? I don't have a clue.

 

Many thanks!

 

~ Bill C.

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I only use polyester resin, simply because that is what is most readily available here, and I'm used to working with it. I don't think there would be a weight difference between the two. Since fiberglass is so durable, you won't have to worry about the weight of the pieces. As long as you don't get carried away and make the piece too thick (too many layers of fiberglass and resin), the weight shouldn't be a concern. My Mara shin guards are very light, and they've held up to a LOT of trooping!

 

I have bonded leather strips into fiberglass armor pieces, but I've never tried it with velcro. It would certainly stick well if the fibers are able to soak up enough resin to form a bond... but my concern would be that the resin might soak through and render the velcro useless. The best thing to do is to make a test piece. Just lay up some fiberglass, and try applying the velcro. If it works, then your'e free to move ahead. If not, then you can always apply the velcro to the back of the armor once it cures.

 

Happy costuming!

 

Pam :-)

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Does anyone here know the relationship between fiberglass cloth/mat and the thickness of the finished product?

 

I need the shoulder bells to be about 1/2" - 5/8" thick, and the Breastplate to appear to be about 5/8" thick. I'm not too worried about the BP, as I can just make the edges look thicker, while leaving the middle section thinner. Nobody will see the back side of it.

 

With the bells though, the top edges will ride about an inch off my shoulders, and the underside may be visible at that point.

 

What thickness/weight of glass (mat, cloth, veil, it's all confusing to me still.. :P ) do people use? How many layers would it take to make the casting 1/2" thick? How flexible is the mat? How much thicker is the mat than cloth?

 

Any clues on this are greatly appreciated, as I'm not sure what materials to get. :(

 

Thanks all!

 

~ Koda

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You really do NOT want to cast anything 1/2" thick, trust me! It would take a massive amount of fiberglass and resin, and it would weigh a ton. The proper thing to do is to create an illusion of depth, as you mentioned. Super-thick fiberglass isn't a good option. Even my thickest fiberglass castings are cinsiderably less than a quarter inch thick.

 

Fiberglass matt is best for large areas without a lot of detail. It's the workhorse of the fiberglass industry, and comes in various fiber densities. Fiberglass cloth is best for small areas, curves, and detail work. The two can be used together as needed, also. For either one, I wouldn't go any thicker than 5 layers.

 

If you truly need a very thick look, I would make it hollow. Cast the top, cast the bottom, epoxy them together, and fill/sand the seams.

 

Pam :-)

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Thanks for the fast re-post, Pam.

 

Wow... :shock:

 

That's.... mildy deflating. :( Kinda puts me back to the design phase again. :P

 

I looked at Thomas' Ganner Krieg armor project pix and it looks like the shoulders are about 1/2" thick. I just assumed he made them out of fiberglass laminate as well as the body plates (which I see now on second look are thinner in the non-cosmetic areas). What did he use to cast the shoulders and handguards?

 

Is there some other casting material that I might try on the shoulders? They still need to be light, but they do need to be thicker. (Need to "build up" the look of my skinny arms and shoulders) :P:? Is there some kind of foam or something that can be layed-up in a non-level mold like the shoulders will be? Something with more viscosity?

 

Or is there something that could be used to build up the thinner fiberglass "shells" after they are cast? Make them a bit thicker?

 

I've thought about maybe building up the insides with softer foam rubber, to add a bit of bulk and padding, and help keep them from shifting during normal arm movement, but I still need to make them thicker at the edges at least.

 

I guess I could fill the "shells" with clay post-casting to shape the insides, then cast separate "bottoms" but man, I'd really like to avoid all the extra crafting if at all possible. :?

 

~ Koda

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Guest Anonymous

Do you prime the fiberglass after you sand it? Or do you just start painting? Will gesso work as a primer for acrylic over fiberglass, or how about mod podge?

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Do you prime the fiberglass after you sand it? Or do you just start painting? Will gesso work as a primer for acrylic over fiberglass, or how about mod podge?

 

You're working on a Sith Lord... it's time to turn off your artsy-craftsy mind, and turn on the workshop mind. Watch an episode of Home Improvement, go out to the garage and belt out an "arr arr arr!" a couple times, and then you'll be ready. (I always feel so feminine while standing in the shop in a respirator and goggles!)

 

Yes, it is a very good idea to prime the fiberglass before painting it. No, you should not use arts and crafts materials. Automotive and/or sandable spray primer is best. Acrylic enamels like the kind used for model cars are good, soft acrylics such as Liquitex or Apple Barrel are not. Soft acrylics can be used for thin weathering washes, but they should not be used to paint the fiberglass itself. One good bump against something, and the paint could scratch right off.

 

Pam :-)

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Guest Anonymous

Lol, believe it or not, I have access to a full workshop of materials. I am about to get our industrial sander out right now and go to town on my mask with my respirator and rubber gloves. :P

 

I was looking at some automotive primer in the shop/garage we have, but I wasn't sure what type of paint that would seal, if it was for acrylic or not. I thought about doing a spray test. But all of the other material I see out there for cosplay has said that acrylics work fine on fiberglass resin glossed cosplay props as long as you sand it. And being a freelance artist, using supplies I already have in over supply seemed like a good idea. Of course, there is tons of metallic automotive spray paint in the garage as well I could take a peek at. But your tutorial stopped just before you got to the painting part, so I was curious.

 

Yes, I am artistically inclined, but thank goodness I am, or believe me, this costume would never have come to be.

 

EDIT: Automobile Spray Primer worked like a dream, for those who may be curious! ;)

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this is the single best tutorial I have ever found for fiberglassing. ive been doing it for a while with NO gel coat and then bondoing the heck out of it I didn't know it was possible to even make your own. what kind of quality of finish do you get when using a talc gel coat???????

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I also find that using fiberglass tape that they sell for drywall works really well since it has an adhesive on one side that is just enough to get the fiberglass to stick to whatever it is you are going to be pouring the resin into without getting in the way of adhesion of the resin. This also avoids those annoying bumps from the fiberglass pulling off the surface of whatever it is laying on. Also works well for backfilling premade stuff!

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Going off silicone for a mold, if you use a silocone brush you can pull the resin off it after you're done. Should be 5 bucks at most in most places food aisles.

 

I may have to grab some tape.

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