Will fiberglass resin harden without enough hardener?

Asked By: Nahed Datdeev | Last Updated: 20th June, 2020
Category: business and finance large business
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There are few things worse than having finished a large project using fiberglass, only to not have it fully cure. You let it sit, and sit, and sit, but it never completely hardens. Chances are you did not add enough catalyst, the chemical that hardens the resin.

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Then, will epoxy resin harden without hardener?

It is only when mixed with an epoxy hardener that they can cure properly. If applied onto a floor without the hardener, the resin would remain a near liquid indefinitely and could not transform into a durable flooring system.

Additionally, will Bondo hardener work with fiberglass resin? Once mixed, the fiberglass resin will cure in 2 hours. Directions for Use Use hardener with Bondo Fiberglass Resin. For small applications use 10 drops of hardener per ounce (2 tablespoons) of the resin. For larger applications, use half of the liquid hardener supplied, to half of the resin container.

Subsequently, one may also ask, how long does fiberglass resin take to harden?

The hardening process begins immediately, so only add catalyst to a working quantity. Once catalysed the resin gradually cures, taking on a jelly-like consistency in about 10-20 minutes before becoming hard in about 30-40 minutes at room temperature (about 20ºC). The curing process generates heat within the resin.

How long does it take for polyester resin to harden?

Adding too much color will slow down or inhibit the cure. During the curing process, the catalyzed resin goes through a series of stages from a liquid to a 'soft gel' in about 15 to 20 minutes, a 'firm gel' in 20- 30 minutes and finally to a 'click-hard' (cured) stage in 1 to 24 hours.

37 Related Question Answers Found

What happens if you put too much hardener in resin?

Adding too much of either resin or hardener will alter the chemical reaction and the mixture will not cure properly.

What do you do when fiberglass resin won't Harden?

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  1. Set the fiberglass in the sun. The curing of fiberglass resin is an exothermic reaction, meaning that heat makes it work.
  2. Use a heat gun on the fiberglass. If the heat of the sun isn't enough, a more intense heat source may be needed.
  3. Spray a mist of catalyst onto the fiberglass with a spray bottle.

What does epoxy not stick to?

Epoxy resin adhesives will bond all woods, aluminum and glass well. It does not bond to Teflon, polyethylene, polypropylene, nylon, or Mylar. It bonds poorly to polyvinyl chloride, acrylic and polycarbonate plastics. The only way to tell if an epoxy will bond to a material is to try it.

Why is my resin bendy?

Resin poured in a thin layer
It can be normal for some resins, when poured in a thin layer, to be bendy. Some resins, especially doming resins, can be flexible after the full cure time. If you want to give the resin extra time to cure, make sure it stays warm and give it another two to seven days to fully cure.

Does tacky epoxy ever cure?


Epoxy that remains sticky after the curing time will stay sticky unless the following measures are taken to repair the situation. If you do not scrape off the wet epoxy, this could result in leaking under the new Epoxy coat. Wipe with denatured alcohol.

Can you apply resin with a brush?

Yes, epoxy resin can be used as a glue. In fact, it may be the strongest glue you will ever use! Mix and stir as usual, and apply as necessary with a brush or foam brush.

Can I use fiberglass resin to seal wood?

Polyester resin is used for laminating fiberglass reinforcement, molds and, yes, waterproofing wood. Laminating resin will become hard but will remain slightly tacky to allow paint or more fiberglass to bond to it. Waxed or finishing resin can not be painted over without removing the top layer of hardened wax first.

How do you make fiberglass resin dry faster?

Use a hot air gun, heat lamp, or other heat sources to warm the resin and hardener before mixing or after the epoxy is applied. At room temperature, supplemental heat is useful when a quicker cure is desired.

Can I put Bondo on fiberglass?

Fiberglass Bondo is waterproof, extremely strong and can be used for virtually any fiberglass panel. As an initial matter, it must be recognized that there is Bondo for metal and Bondo for fiberglass. Ensure that the Bondo for fiberglass is used.

How do you speed up fiberglass curing?


Whats the quickest way to dry fiberglass resin? If you added the right amount of hardener, resin should be dry to the touch in about 20 minutes at room temperature. If it's still sticky after several hours, then try dusting it with talcum or baby powder.

Can fiberglass resin be used alone?

Bondo Fiberglass Resin is the same high-strength polyester resin that is used to build most boats. It can be used alone or with fiberglass tape, cloth or mat to repair damaged fiberglass boats, snowmobiles, jet skis, bathtubs and showers and also be used as a sealer on damaged and rotted wood.

How long until I can sand epoxy?

It takes about 8-10 hours to be hard enough to chisel and sand. Until that point it is chewy and will simply gum up sandpaper. Until that point it is chewy and will simply gum up sandpaper.

What temperature does fiberglass need to cure?

Our Top Tips for Fibreglass Work in Winter
Do not start fibreglassing if the temperature is below 5°C as it will not cure.

Can you sand fiberglass resin?

Fiberglass is a mat of glass fibers commonly used to reinforce plastic. To sand fiberglass successfully, first make sure the surface is completely clean. Remove any stickers and adhesives, then wash it off with soap and water. When the fiberglass is dry, start sanding it with a medium-grit sandpaper.

How much does fiberglass resin cost?


If resin is $18 a gallon and cloth is $1.50 a square foot, how much will it cost him to fiberglass his boat, with one layer of resin/cloth, and two layers of resin on top? Note: There are two types of resin: poly resin and epoxy. Each has it's advantages.

How do you mix fiberglass resin with hardener?

Set the fiberglass in a spot that is easily within reach. Add liquid hardener and resin in a small bowl in proportions as recommended by the manufacturer. Mix the two well using a plastic spoon or knife. Add the resin and hardener to the fiberglass cloth strips using the plastic spoon or knife used to stir the mixture.

Does Bondo cure without hardener?

Bondo doesn't “dry”; it cures through a heat-generating chemical reaction between the resin and hardener. In theory, properly mixed Bondo can be applied in any thickness, but beware of gravity-induced sagging. Bondo mixed to the color swatch will begin to cure in less than 10 minutes at room temperature.