POLISHING A HIGHLY OXIDIZED GEL COAT SURFACE
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?
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.
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.