2347 Gold River Road Unit J — Sacramento, CA 95670 — Phone (916) 635-5424

We get asked commonly about reconditioning older gel coat. Boat owners are concerned about damaging the finish when they polish and wax their boats. This article will cover the basics of polishing and waxing sun damaged gel coat beyond the limits of hand polishing that the owner can readily perform. If the damage is slight enough that hand polishing will suffice, the same techniques will work, though the products will be different.

Let’s start with definitions. The words ‘rubbing compound’ and ‘polish’ are a common source of confusion. Manufactures use these words interchangeably and they refer to a liquid or paste that contains some degree of abrasive grit. There are ‘heavy’ and ‘light’ compounds that only differ in the degree of abrasiveness.  (We use a wax product called a polish by its manufacture that has no grit in it at all.)

Gel coat, like paint, fades (changes color) and oxidizes (chalks over) due to exposure to UV light over time. Polishing removes a thin outer layer of gel coat exposing less damaged material underneath. Oxidizing tends to be a surface effect while fading is much deeper in the material. A dull oxidized surface may restore to a deep luster with polishing but still leave an uneven color due to fading. This is more prevalent in dark colors but can be seen even in off-whites.  If the color has faded, no amount of polishing will restore a uniform appearance. We occasionally are asked if wet sanding, or color sanding as some know it, with ultra fine sandpaper will eliminate this effect. Wet sanding works like a very aggressive polish and will not reduce the fading. It will however, reduce the life of your gel coat by thinning it out and is not ever recommended. An additional issue with heavily oxidized gel coat is stability. It is not uncommon for a dark color to polish to a deep bright finish only to bleach back out within a year regardless of the type of wax or sealer used. If this happens, the only ‘fix’ is new gel coat. If we are not sure of the stability of older gel coat to be polished, we will polish a sample area and send the boat home for a few months for the owner to watch. If the polish is holding, the restoration will likely work.

So how do I do this?

Tools:

Gel coat needs heat and abrasion to polish. This is best accomplished with a rotary, (circular), motion electric or air powered tool. The tool should spin at about 2500-3000 RPM. If you look at most grinders they will be rated at 7000 and higher RPM. This is much too fast to work as a polisher. A tool designed to spin with a dual action pattern will not generate sufficient force and should not be used.  

Polishing pads are available in three primary styles, wool, wool/polyester blend and foam. These can be thought of as different grits like sandpaper has. Wool is the most aggressive and is used for heavy cutting of oxidization and scratch removal. It will also leave swirl marks in the finish that will need to be removed by finer polishes. Wool/poly blend is a medium duty pad and is used as a follow-up for the pure wool or as a primary pad for lighter polishing needs. The foam style pad is used for application and polishing with a sealer glaze and is the least aggressive of the three. Many pad manufactures (though not all) color code their pads with wool being white, wool/poly blend is yellow and foam is black.

Polishes/ Compounds:

There are many brands of fine polishes on the market, too many to cover in a single article. I will focus on products we use in our boatyard but other brands will have comparable items.

For highly oxidized and/or faded gel coat you will need to start with a ‘heavy’ compound. I would use 3M 05955 Super Duty Compound. It is a thick liquid with a very abrasive grit. When combined with a wool pad it makes for rapid material removal and scratch removal. Starting with a clean gel coat surface apply a thin film of compound using a damp rag to spread the material. It is common to see boat owners use the ‘more is better’ method. Resist this desire. A thin film is all that is needed. Start the machine and slowly move the pad left to right and up and down over the polish area. Work on an area about two by two feet at a time. The compound needs to stay damp. If it is drying before you can get to it, reduce the area covered at a time. The polisher should be held at a slight angle to the boat so most of the pad is in contact with the surface. Move over the area until all the polish has been pulled into the pad then continue for 30 to 45 seconds.  Make two passes over the work area with this technique and look at the finish to see if it is doing what you want. If the air temperature is high enough that the polish is drying out too quickly, wet the applicator rag with more water. You need to apply some pressure to the pad while running the machine, the amount of which you will need to discover by trial. We usually start with ‘more’ pressure and back off to ‘less’ as the polish is consumed.

After two passes with this compound, rinse off the boat with water and see if the oxidization has been removed. You can make additional passes over the entire boat or small areas if you think it’s needed. The pad must be kept clean during this process. Look at the pad surface frequently as compound will build up in the fiber. As the first small clumps of compound become visible in the face, remove the pad from the tool and flush it with a water hose. Spin the pad dry and begin the process again.   

This process will likely have removed all the fading and oxidization that is going to get removed but left the finish with swirl marks and with a moderate shine. You may proceed to wax at this point or move to a finer polish to improve the surface luster.

If you want to increase the shine, I would recommend 3M 06039 Finesse-It Compound. When used with a wool/poly blend pad, it will remove most of the swirl marks and deepen the shine. This material is a paste and can be applied with a paint brush or clean rag. Again, use it sparingly. Polish with the same technique as the Super Duty, about a two foot square, side to side motion and more pressure to less as the polish is consumed. Keep the pad clean. Wash the surface again.

You can now proceed to wax. Wax types based on naturally occurring compounds, carnauba, bees, paraffin have a long record of use and work well but tend to erode when washed with water and detergents.  Synthesized waxes, those with silicone, Teflon polymer based, tend to not be water soluble, have UV shields incorporated and will have a longer life. We use a polymer product called ‘Driven’ that has worked very well for us. Apply two coats of your chosen product following package instructions and you are finished.

There are additional steps that can be taken with additional products that we do use depending on the condition of the surface and the desired result. If you are not getting the results desired with this approach, call our boatyard and we might be able to offer you a suggestion that would help.

A repair to a non-skid surface presents different issues than repairs to a smooth surface as the texture will need to be restored. This article will focus on repairing a small area of damage, in this case, a fastener that has cracked the surface. Much larger repairs are possible but require an alternate approach.

1. In the first image  you can see the result of a fastener from the interior of the boat that has cracked the deck. Begin the process by removing the screw and installing a shorter fastener. (If the fastener is not accessible, it is possible to leave it in place.)

2. Using a burr type of abrasive bit, grind away the loose material from the gel coat surface and underlying fiberglass. Take care to chase any fractures in the gel coat as well. You should be left with a shallow depression in the surface with smooth edges. If the fastener is still in place, grind the tip down as well to get it below the surface at least 1/8”.

3. If the depression in the surface is greater than 3/16”, you will need to fill it with a filler prior to casting the finish in non-skid texture. If less than 3/16” you can skip to step 6 to proceed with the gel coat portion of the repair.

4. If a filler is needed an epoxy like MarineTex is a readily available and well suited to this work. You can alternately use a polyester filler (like Bondo) although it may not be as durable. Some epoxies (like WEST Systems) are high quality materials but may not bond well to the polyester gel coat you will use to finish this work and are not recommended. Mix your chosen filler per package instructions and apply it into the void leaving the material below the surface of the surrounding gel coat.

5. When your filler has cured, take the same burr you used to begin the repair and grind the filler to a uniform depth about 1/8” below the nonskid surface.

6. Now you can prepare the stamp mold with the texture. Select an area on undamaged nonskid near the repair site and clean it thoughly. Allow the area to dry and brush on a wet coat of PVA release agent This material will dry to a thin film that will prevent the mold material from sticking to the surface. When dry to the touch, mix up some of the polyester filler and place about a 1” diameter ball onto the dry PVA surface. ( 1)With a clean paint stick or putty knife pat the filler into a flattened shape about 1 ½” in diameter and ½” or more thick.  As the filler begins to cure and thicken up, place a small stick vertically into the mass and hold it until it is cured enough to support the stick to create a handle. Allow the filler to come to a full cure.

7. Remove the stamp mold by pushing on one side of the handle. Sand two or more of the edges on the mold to a break in the pattern. This will help to properly align the mold later. If there are air bubbles in the mold face, you will need to use an intact area of the mold over the repair or recast the mold if the air is too widespread.

8. Set the mold over the repair area and twist it around slightly to feel it ‘lock’ into the deck pattern. This may take rotating the mold around until the pattern lines up. With the mold sitting on the deck ‘locked’ in, place a layer of masking tape on the deck along two sides of the mold for a visual reference later.

9. Clean the mold with water to remove any PVA from the casting process, allow to dry, and coat the face and sides of the mold with a new application of PVA and allow that to dry. Additionally apply PVA around the repair area taking care not to get the material inside of the repair itself.

10. You are now ready to cast the gel coat pattern. Mix up a quantity of gel coat following package instructions. Fill the remaining space of your repair area with gel coat using drops off a small stick or similar tool. You are trying to slightly overfill the space. Avoid placing gel coat outside the repair area. If you can sight across the repair area, you would want to see a slight round of gel coat above the surrounding deck. When you have filled the repair area, bring the prepared mold straight down onto the deck using the masking tape as sight lines. Gently push the mold back and forth to ensure it has dropped into the pattern. Allow the repair to cure.

11. When the gel coat has cured, lift the mold off the deck. There will likely be some ‘flashing’ of gel coat beyond the mold from the material displaced. This can be trimmed back with a sharp razor knife. Wash off any remaining PVA and your done!

MATERIALS AND TOOLS NEEDED

Materials
PVA (Mold Release)
Polyester Filler (Bondo)
Gel Coat
Masking Tape
Stir Sticks

Tools
Drill Motor or Dremel type tool
Metal burr grinding bit
Paint Brush
Safety Gloves
Safety Glasses