Gloss Coat/Polish (Optional)
Gloss coats are essentially a second hot coat that is fine sanded, compounded, and polished to a shine. Typically, gloss coats are found on longboards and retro-style boards, where weight isn’t a factor. Adding a gloss coat increases the weight of your board, so typically high-performance shortboards skip a gloss coat and are considered done after fine sanding the hot coat to 400 grit or so.
If you are making a longboard, tinted board, or opaque pigmented board, the colors will really pop when they are glossed and polished. The process requires some specialized materials and tools (all borrowed from the automotive finishing industry), all of which you can get in Greenlight’s Gloss/Polish Kit. Glossing/polishing epoxy has always been considered more difficult than doing it on polyester resin, but the truth is, you can get a really nice shine on epoxy by using a few higher grits of sandpaper before switching to your compounding bonnet.
Brushing on your Gloss Coat
The process for applying your gloss coat is nearly identical to applying a hot coat. Since you already have a smooth, sanded hot coat, you need a little bit less resin for your gloss coat. Still, plan on about 1oz of mixed material per foot of surfboard length, and don’t forget about your 2 capfuls of Additive F to help the resin flow evenly on the board. Just like hot-coating, you want to tape off your rails with high-temp masking tape to keep drips from running down the rail. Also, if you aren’t satisfied with the sharpness of your tail edge, you can use the gloss coat as a second chance to square it up with a small tape-dam in that area.
A little trick while glossing is to use a razor blade to scrape away the bump of epoxy left along the tape border once the epoxy has set up and is no longer tacky. It is easier to scrape away this small line of epoxy when it is soft (but not sticky). Do this twice (after you have glossed each side of the board), as it will make your final sanding/polishing step easier.
Fine Sanding the Gloss Coat
Once your gloss coat has cured, you should have a nice, shiny flat finish that is ready to sand. Since you did a lot of the rough sanding on your hot-coat, you start sanding your gloss coat with higher grits. Most glossers start with 320 grit and remove the shiny surface first (don’t worry, it will come back). Make sure to keep your sandpaper as clean as possible, brushing the buildup off with a wire brush. Once you have sanded away the shine, you need to work your way up with progressively higher grits of sandpaper. Each grit removes the scratches left by the previous grit.
After 320 grit, move to 400, still using your power sander. You may also want to start wet-sanding at this stage. From 400 grit, you may want to switch to hand-sanding with a soft or medium sanding pad. The progression of grits should be: 600, 800, 1000, 1,500, and finally 2,000. You should wet sand all of these grits, as it helps keep the sandpaper clean and cutting evenly. Run your sanding pad nose to tail and tail to nose during these stages. You want to avoid going rail to rail or in circles, as you are just trying to remove the fine scratches from the previous grit.
Once you have wet-sanded to 2,000, it’s time to break out your wool compounding bonnet and compounding liquid. You need to use your variable speed sander/polisher for these final steps. The goal with the compound is to squirt it on the board and spread it around while it’s still in liquid form. Typically you work in sections with the compound, spreading it around and buffing the board until the compound dries in a haze. Once that section is dry, move on to the next section. Finally, when all of the sections are dry, you basically buff off the compound with your polisher/sander. Don’t forget the rails. You should be covering the entire board with the compound. You can do the whole thing with the power polisher. No need to hand-compound at this stage. Once the compound is buffed off, hand-wipe the entire board with a microfiber cloth to remove any compound residue before you start the polishing stage.
The final step in the process, polishing requires use of a polishing compound (finer grit) and polishing bonnet (typically foam). Besides these two components, the polishing step is essentially the same as the compounding step. Work section by section, and don’t forget the rails. Once the polish has dried to a haze, you buff it off with your polisher and you won’t believe your eyes. The board should be back to it’s original post-gloss shine. At this stage, take one final pass with your microfiber cloth, and you are DONE.