There are many common fillers used with gelcoat and resin and here we’ll help you pick the one that is right for you.
When using putty, a good rule is not to go higher than 1/8″ thick without adding a layer of glass to prevent any issues. With the various fillers, for the right working consistency, you’ll want about 60-70% mix to resin ratio.
Milled Fibers: Finer than chopped glass, makes a harder putty that is strong and coarse.
Walnut Shells: Brown in color and preferred for wood putty or nonskid since it has large particles. Good Strength and darker pigment.
Microballoons or Microspheres: Phenolic spheres are generally plastic or glass and hollow, intact spheres that are lightweight. This is ideal for making fairing compounds. The Microballoons are a more expensive option for filler.
Fumed Silica: Also known as Cabosil FIller or Aerosil Filler. This is a hydrophilic fumed silica. Fumed Silica provides little change to weight, color, or physical properties after cure, used in resins and gelcoats to make them hang on vertical surfaces, (too much can cause porosity.)
Cotton Flock: Made from pieces of cotton and thickens to an off-white color. Great for bonding many substrates, especially wood. The mixture also creates a multipurpose adhesive for many other substrates in addition to providing excellent substrate wetting and penetrating characteristics. Increases impact and abrasion resistance.
Chopped Glass: These are the biggest pieces of fillers and are most popular for use with resin putty. Perfect for corners, crack resistant, and doesn’t affect pigmented gelcoat. 1/4″ glass fibers make the strongest glass reinforced putty.
There are many ways to repair spider cracks in boats, using our Gelcoat Repair Putty is an easy and fast way of doing it!
First, you will need to determine your spider cracks are only that, spider cracks. To do so, you will need to inspect the area for any sign of broken support. If the surface is steady and looks solid, then you have spider cracks.
In order to properly fix any spider cracks, you will have to open the cracks to fill them up correctly. This can be done by using a Dremel. Once the crack is open and it has a good size you can sand and clean the area. For cleaning, you may use acetone or soap and water.
Now, you are ready to use the Gelcoat Putty. Mix in a 1-1/2% ratio of MEK-P Catalyst into the putty and mix it properly. Use a putty knife to fill in the spider cracks. Once dry, sand the surface to a smooth finish.
For filling gauges and cracks, some tips:
This product uses MEKP, just like gelcoat so your working time is 8-18 minutes, depending on temperature. If catalyzed at 1% and it is in perfect conditions (77 F) you have a longer work time. To extend work time cool product down before use.
If filling holes, fill a little high to allow for shrinkage. Once it dries you can easily smooth it out with sandpaper. Recommended thickness at 1/4″.
Gelcoat does not fully cure without first supplementing it with a surfacing agent or wax additive sanding aid. Gelcoat may be thinned for use in a Portable Preval Sprayer with styrene monomer. You can spray it with polyvinyl alcohol (PVA) before gelcoat reaches its gel stage (5-10 min.), or add 1oz per quart of a wax additive sanding aid.
PVA or Partall Film #10 is a release agent that helps with removing parts from a mold or can be used as a surfacing agent when using gelcoat without a wax additive (sanding aid).
PVA is soluble in water making it easy to wash off. Applying can be achieved by spraying or wiping the green liquid on with a sponge. It will foam slightly but dry to a clear, glossy shine. It can take 15-30 minutes depending on temperature.
For spraying gelcoat our FGCI brand does not recommend thinning.
Generally, you should not add more than 10% Styrene by volume. Patch Booster is an additive that will thin out gelcoat and not affect colors. Follow manufacturers instructions as added Mekp may be needed.
Another thinning alternative is the Duratec High Gloss Additive. This is used with gelcoat for many reasons. Mixed at a 50/50 ratio this will produce a high gloss finish and will serve as a thinner for your gelcoat, that is why this is commonly used when spraying gelcoat. In addition, you’ll omit any additional sanding aid. After waiting a full 24 hours you can buff when cured, for a hi-gloss use 600 or higher grit paper and buff with Aqua Buff 2000 compound. Follow the manufacturer’s technical data sheet as an extra hardener may be needed. Some customers use Styrene for thinning but the manufacturer warns it can affect the gelcoat colors although this is the most cost-effective option and doesn’t have the added wax.
The finish of your fiberglass pool steps can fade after years of use and exposure to pool chemicals and the weather. If you notice that your pool steps are looking tacky it might be time for you to reapply gelcoat to them.
You can use Gel Coat if your pool steps currently have gelcoat or bare fiberglass for pool use. We don’t recommend the brushable gelcoat in pools because the chemicals can affect the gelcoat lifespan.
Brushable Gelcoat, often referred to as gelcoat paint, is a specially formulated product that is made to be applied like paint and eliminate the need for spray equipment. It has excellent leveling, Water/Osmosis resistance, UV light Stability, great Gloss Retention, and fantastic long-term durability and is available in a variety of colors. Here are some tips for successful brushable gelcoat application.
Applying Gelcoat by Brush or Roller – (Use a Brushable Gelcoat) When applying gelcoat by brush or roller, we recommend the Ultra Plus Brushable Gelcoat. (other Gelcoats are best applied by Spray) The Ultra Plus Brushable Gelcoat is designed for self-leveling and is a much easier application. It allows for a much smoother finish and less time for finishing the gelcoat. It is easy to use for the “do it your selfers’! Choose a good pure (natural) resin-resistant bristle brush with tapered ends. Avoid brushes that are either too stiff or too soft. For most work, a 3″ or 4″ wide brush will suffice. If there is a trim color, you should have a narrow trim brush on hand. Our Brushable Gelcoat comes with an MEKP hardener with every purchase, but you may need more which you can purchase as an option depending on the application, temperature, and other environmental factors. Gelcoat needs to be applied evenly. We suggest a thickness of 18-20 mils to properly cure. The thickness of the matchbook cover is approximately 18 mil. If you’re not sure how thick it is, pick up a mil gauge. This is a simple, easy way to see the thickness of your gelcoat.
Don’t add Patch Booster or Sanding Aid (wax). You don’t need to add sanding aid (wax) to Brushable gelcoat to have it dry tack-free. The self-leveling technology added doesn’t require any additional products or additives.
Proper gelcoat application requires you to apply your coats about 15-20 mils thick. We offer mil gauge for purchase.
Allow the gelcoat to cure overnight and then lightly sand it and buff it for an outstanding shine!
Use Acetone for your cleanup. Just like other Polyester-based products, Acetone is the best cleanup material!
The most important step: Adding the proper amount of Catalyst. We recommend 1.5%-2% Catalyst ratio. After adding the catalyst, you will want to mix for two minutes, preferably with a mechanical agitator (drill mixer). For your reference, here is the catalyst chart so you know exactly how much catalyst you need.
Brushable gelcoat is not recommended for pool surfaces.
Tips 1 mL = 1 cc If using wood mixing stick, place stick in resin before adding catalyst so wood doesn’t absorb catalystOnly catalyze slightly more than needed. Resin that cures still in the mixing pot is unusable.
Be sure to have a good strategy when applying your gelcoat. Once you mix and catalyze, you have about 15 minutes to apply the gelcoat before it starts getting hard or starts to “gel.” The actual working time depends on the amount of catalyst and how hot the working conditions are. Anything below 60 degrees and your gelcoat will not cure, but as you get warmer and warmer, your working time will decrease rapidly. At 70 degrees, you get 15 minutes, but at 90 degrees, you only get 5 minutes. If you need more time to work, be sure to sit the can in some cold ice water to cool it down to 60 degrees to allow you a little more working time.
Here are some helpful tips on how to work with brushable gelcoat, especially during the warmer months.
Cooling the gelcoat, by refrigerating the product to around 70 degrees, will give you up to 15 minutes of working time.
Humidity can be another factor, so, make sure the mold and surrounding area is dry before applying your brushable gelcoat.
Make small batches of gelcoat at a time and catalyze at 1 ½ % to avoid the material from getting hotter. When spraying the gelcoat, make sure you catalyze at 2 %. If you choose to use Duratec, please note, that the product must be cool as well.
If you seek to roll on the gelcoat, the product should be applied evenly at 14 mil thick.