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Our FAQ section is here to answer the most commonly asked questions. We have also added a glossary of terms in pdf form for your ease of use, feel free to download the glossary and use it as a reference.

Please take a look through our How To page if you can’t find the answer here. If it is a process you are wondering about you are more likely to find it there. It carries step-by-step instructions on several projects for do-it-yourselfers.

If you cannot find the answer to your question on the site please e-mail technical support or call us at 800-272-7890, one of our experienced techs will answer your question.

Glossary Of Terms

Different amounts of resin are required to wet out different forms of fiberglass.

For example, one gallon of resin will wet out approximately the following amounts of fiberglass:
40 square foot of 8 to 10 oz. cloth
50 square foot of ¾ oz. mat
30 square foot of 1½ oz. mat
35 square foot of 24 oz roving

In the event successive layers of glass are laid up before previous layers gelled, coverage will be greater.
The appearance of a hard white build up on the mold surface is commonly mistaken as evidence of styrene in the parting wax or wax build-up. The white substance is more likely styrene that has migrated from within the mold to the surface and broken through the wax barrier. Styrene molecules in the mold are attracted to styrene molecules in resins used to form the part and will bond if allowed to come into contact, causing the part to stick.

Waxes are applied to mold surfaces prior to the molding process in order to prevent bonding. However, heat generated during the molding process gradually softens wax and can inhibit its effectiveness as a barrier. In order to prevent styrene migration between mold and part a polyvinyl alcohol film (PVA) such as Partall ® #10 should be used in conjunction with wax. If applied properly, PVA creates a solvent resistant, yet water soluble barrier through which styrene molecules cannot penetrate. Wax and/or PVA must be applied properly and adequately in order to form an effective barrier.

The use of PVA is particularly necessary on new, repaired or reconditioned molds. Once a mold is seasoned wax alone is normally sufficient as a barrier when applied as needed but PVA can certainly be used as extra protection against costly and time-consuming molding hang ups, particularly on very large, intricate, or expensive molds.

If styrene migration does occur you will need to recondition the mold surface. This type of build up usually requires stripping down the mold with a proprietary mold cleaner or in extreme cases a power sander until styrene is no longer present on the surface. In some cases buffing or hand rubbing the mold with fine abrasives or finishing compounds may be sufficient. The key is to remove all traces of styrene build up from the mold surface. Keep in mind that a reconditioned mold should be treated like a new mold in terms of the waxing/PVA process.
These terms usually talk about polyester resins, the first one waxed is an orthophthalic resin used in general fiberglass work where it is usually left a "natural" finish. This resin has a wax added to it to protect the resin and underlying glass fibers from moisture penetration. The wax coming to the surface as the resin starts to cure (dry). for most diy repair projects the resin supplied in kits will be waxed resin.

The other resin which is called isophthalic resin is sold un-waxed, this resin is also a little bit more expensive to buy, is a higher quality resin being stronger in nature, has better chemical resistance
and is usually the preferred resin used in fiberglass boat building and repair work as it can be left for a day or two without sanding prior to further laminate build up.
Wax is best added to this resin on the last coat if it is being used under a boat floor/hull situation or left without surface finishing (e.g. painting) to protect from moisture entry.
The science of liquid movement is called “fluid dynamics”. We will take a look at two (2) simple parts of this known as “viscosity and thixotropy”.

Very simply, the “viscosity” of a liquid is how thick that liquid is. “Viscosity” can be measured in a number of ways and with different units of measure. Commonly used units of measure include stokes, poises and centipoises (cps). Scientifically speaking, it is the resistance of the liquid to oppose the energy being used to move it.

By examining water, which has a very low viscosity and comparing it to the “viscosity” of honey, which is higher, it would be much easier to stir the water and use less energy than stirring the honey. Both water and honey are called “Newtonian” fluids. This means the energy needed to move these materials is directly equal to the speed at which they are moved.

For instance, if it takes one unit of energy to move water at 1 mile per hour, it will take two (2) units of energy to move water at 2 miles per hour. It is directly proportionate.

“Thixotropy” is how much body or fluffiness there is in a material. A good example of a highly “thixotropic” liquid is mayonnaise. Mayonnaise has a high “viscosity” when stirred slowly but a much lower “viscosity” when stirred quickly. Because “thixotropic” liquids are called “Non-Newtonian” fluids, this means the energy to move them is NOT directly equal to the speed at which they are moved. So as in the above example of mayonnaise, “thixotropes” have a high viscosity when moved at a slow speed and a lower viscosity when moved at a higher speed.

The ratio of the slow speed viscosity or the “high speed number” divided by the high speed viscosity “low viscosity number” is called the “thixotropic index”. This refers to how much body the material has, how well it will hang and how well it will resist sagging, due to gravity.
Unsaturated Polyester Resin Solution: Unsaturated refers to carbon-to-carbon double bonds, which have the ability to open up and crosslink with other unsaturated molecules such as styrene. The breakdown of the word polyester is poly meaning many and ester being a certain type of chemical connection that binds these molecules together. A solution indicates a mixture of different molecules; those that will crosslink together like the polyester and the styrene and those that will control the rate of the reaction such as the cobalt and various aniline accelerators.

There are basically 4 different types of Unsaturated Polyester Resin Solutions, which we sell and they are the low profile DCPD, Orthopthalic, Isopthalic, and Vinyl-Ester. The type of resin produced is dictated by the raw materials, which are used to make the polyester molecule and will result in these products having different end properties and different associated costs. While resins may be fit into these different classes, keep in mind many manufacturers will blend them together for their different products.

DCPD Type Resins are based on a chemical called Dicyclopentadiene and form a type of resin called Low Profile. Low Profile indicates resins, which are typically harder with less shrinkage, and most importantly, resist the tendency for resins to “print through”, that is to show the profile or outline of the underlying fibers of glass, carbon or aramid through the gel-coat surface.

Ortho Type Resins are based on Orthopthalic acid. These are the general purpose resins used in thicker laminates to build up thick sections of composites. They are easy to work with and usually cure with a slightly tacky outside layer, which is good in that it provides better inter-laminar adhesion to additional layers. The engineering parameters of these products such as tensile strength, flexural strength, impact resistance, and fatigue resistance are best described as good but not best.

Iso Type Resins are based on Isopthalic acid. These are generally considered a higher class of resin and a little more costly. They are not quite as user friendly but have improved engineering parameters such as tensile strength, flexural strength, impact resistance, and fatigue resistance. Additionally, they will also have much improved water and chemical resistance.

Vinyl Ester Resins are based on liquid epoxy resins. These Resins are considered the premium product in performance as well cost. Their downside is they have a tendency to foam with the wrong catalyst, which can result in porosity. The bigger advantages to these resins are their fatigue resistance and their high temperature resistance for chemicals and solvents. This makes them useful for a number of applications where no other product would suffice such as tanks for acid baths and containment for other chemicals. Additionally they have excellent water resistance and have become the resin of choice as a moisture barrier coat for submerged applications such as boats and pools.
Yes, we do! We can match anything from a hatch, down to as small as a 2” x 2” sample; the bigger the sample, the more accurate the colormatch. We use a photospectrometer to get an exact match from your sample and can make as little as a gallon of your color.
Here’s what you need to do:

Mail us your sample in an envelope with your name, your contact info and how much you want made to

Fiberglass Coatings, Inc.
4301 34th Street North
St. Petersburg, FL 33714
Lots of people will spray gelcoat on a surface to get a better finish, but they are not putting their water traps in the right spot and getting water in the gelcoat, which will cause the gelcoat not to cure completely.

Water traps need to be at least 10 feet to 15 feet away from the compressor so the air has a chance to condense and the trap can do it job.

A water trap is needed at the gun as well to make sure you are not getting any water, water will neutralize the mek-p and the gelcoat will not cure right.

The only way to fix that is to wash the surface with acetone or lacquer thinner until the gelcoat is tack free enough to sand and reapply new gelcoat.
Properly applying gelcoat is the key to a good finish. Many of our customers are hesitant to use it, thinking it’s too complicated or they think they can’t end up with a good finish. So, we are here to provide a step-by-step guide on how to properly apply gelcoat. As with all our products, if you have any questions, we are here to help!

First thing you want to do is look at the surface you want to apply gelcoat to. If the surface is already covered with gelcoat, or if the surface is a fiberglass, or polyester resin, then applying gelcoat will be a snap. If the surface is paint, then the paint would have to be removed before applying the gelcoat. So, you’ve decided the surface is gelcoat, so it’s time to begin. You want to sand the surface to create a mechanical bond with the gelcoat. Start by sanding the surface with 150 grit or lower sandpaper. Our technicians recommend using Dyekum Steel Blue to be very thorough. Steel Blue is a dye you wipe on. Once you don’t see the blue dye anymore, you know you have properly sanded everything. You can also use a pencil, but it’s harder to see and won’t guarantee complete coverage.

Next, you want to clean the surface. We recommend using Acetone, as it doesn’t leave a residue and evaporates quickly. Once the surface is clean, you want to get going pretty quickly; if the surface sits for any extended amount of time, you will want to re-clean the surface. Dust and dirt particles are your enemy here, so be thorough on the cleaning.

We are ready to gelcoat! First, decide if you need one or two coats of gelcoat. It will take a minimum of two coats of gelcoat if you are changing colors. If this is going over a patch, we recommend 2 coats at least, to get a nice, uniform surface. Otherwise, one coat will do.

Gelcoat needs to be applied relatively thin. We recommend 18 mils thick, to properly cure. 18 mils is approximately the thickness of a matchbook cover. If you aren’t sure how thick, pick up a mil gauge. It’s a quick, easy way to see the thickness of your gelcoat.

Gelcoat requires Methyl Ethyl Ketone Peroxide or MEK-P to activate the hardening process. The amount is very small. We recommend 1-1/4% to 1-1/2% by volume, which means 13-15cc’s per quart. Darker colors require a bit more catalyst for the same reaction, so you can catalyze up to 2%. Refer to the catalyst chart on the side of the can, or you can find one HERE.

Be sure to have a plan of attack for applying your gelcoat. Once you mix it, you have about 15 minutes to apply the gelcoat before it starts to get hard or “gel.” The actual working time depends on your amount of catalyst and how hot your working conditions are. Anything below 60 degrees, and your gelcoat will not cure, but as you get warmer and warmer, your working time decreases rapidly. At 70 degrees, you get your 15 minutes, but at 90 degrees, you only have about 5 minutes. If you need more working time, be sure to sit the can in some cool water, or even some ice to cool it down to 60 degrees give you a bit more time.

For applying your gelcoat, you can either roll the gelcoat on, like paint, or you can spray it on. We also sell a Brushable Gelcoat that can be applied with a brush. If you decide to roll on the gelcoat, be sure to use a solvent-resistant 1/8” or ¼” nap. Be sure not to use foam rollers, as they tend to leave bubbles. If you brush it on, be sure to use a solvent resistant brush. Your first coat will simply consist of the gelcoat and the MEK-P catalyst. Once applied, you want to wait about an hour and a half, for the gelcoat to set. It won’t be completely cured by then, but it should be hard and tacky.

Your second coat will consist of the same amount of Catalyst, but if you are doing one more coat, your next coat will include Sanding Aid, or ‘wax.’ You will mix in 1 oz per quart to the gelcoat, which will seal the surface from oxygen, causing the gelcoat to dry tack-free. If you roll or brush your seconding coating, be sure to go the opposite direction from the previous coat, allowing a uniform coating.

If you are using our standard Exterior gelcoat, you will be ready to sand and buff your freshly gelcoated surface. If you are using our brushable gelcoat, you will want to let it sit overnight to ensure it’s completely cured. To start sanding, begin with 320 grit sandpaper and sand the surface completely. From then on, start going up to 400, then 600, and finally 800 grit sandpaper.

At this point, you can use an 800 grit compound to compound the gelcoat. You want to use a buffer that turns at 1600-3000 RPM’s. The car polishers will not work, as they spin too slowly, so you want to check the spin speed. It’s best to do a 4’ by 4’ area and go from there. Every 10’ or so, you will want to clean your pad with a spur or with some air to ensure pieces don’t scratch your surface.

If you want a beautiful, glossy shine, use a machine glaze and then two coats of wax, and you will have a beautiful finish that any professional would be envious of.
At ¼” thick, you get 6 sq. ft per gallon, or 1-1/2 sq. ft per quart
At 1/8” thick, you get 12 sq. ft per gallon, or 3 sq ft per quart
At 1/16” thick, you get 24 sq. ft per gallon or 6 sq. ft per quart
At 1/32” thick, you get 48 sq. ft per gallon or 12 sq ft per quart
At 1/64” thick, you get 96 sq. ft per gallon or 24 sq. ft per quart
A 2 gallon kit of 2lb Foam will expand to 8 cubic Feet
A 2 gallon kit of 4lb Foam will expand to 4 cubic Feet
A 2 gallon kit of 8lb Foam will expand to 2 cubic Feet
The gelcoats and resin are designed to be sprayed by equipment that sprays the MEK-P into the fan. So when you work them in a mass, they want to chemically react in a hurry. In the summer, chill the product first to about 60 degrees, this will increase working time in a mass to about 15 to 20 minutes for a quart instead of five minutes and it will still cure right in a film on the surface with the right amount of MEK-P. We don’t recommend mixing more than 1 quart at a time.

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