I’m posting this in case others can benefit from this little journey I took last week while finishing up my second board. I found myself with a few minor sand throughs in my gloss coat. This board has a PU foam core laminated with PE resin. At a minimum I wanted to seal those sand through areas, but ideally I wanted to both seal them and make them disappear, so I did some reading on swaylocks and tried a few things.
First I tried rattle cans of both krylon acrylic gloss clear coat and rustoleum clear lacquer. I taped off the areas with very thin scotch tape, and sprayed several coats. When dry and I removed the tape it looked good except for the ridge created at the tape line. Sanding with 600, 1000, and 1500 grits (wet) I removed the ridge, but in most cases I created new sand throughs or re-exposed the original sand through. I then buffed those spots with the wool bonnet and surfboard polish #2, so I restored the shine, but still had sand throughs. I then tried the lacquer by spraying with a stencil held about 1 inch above the surface of the board, eliminating the need for tape and the associated sanding of the ridge line, but this didn’t work so well either.
I tried a similar approach with gloss resin, applying a very thin coat by rubbing on with my finger, but I was not able to fair that into the rest of the surface without re-exposing the original sand throughs in most cases.
I was about to do a second gloss coat on the whole board and be done with it, when I came across some posts about concrete sealers being used to seal boards with sanded finishes. I gravitated towards the posts by McDing and others regarding Behr Low Lustre Sealer since my local Home Depot had plenty, and since there were many posts and lots of info regarding how to apply it as well as the wet look version, how to buff with scotch brite pads, etc.
Considering I was looking for a traditional glossy polished mirror finish I opted to buy some of the Behr wet look sealer. What I wasn’t able to find was any posts that talked about applying this sealer directly on top of a smooth and polished PE resin gloss coat. I wondered if I could just apply a few coats of the sealer without prepping the surface in any way, and I wondered if the sealer would hide the minor sand throughs since the colors of the board are fairly dark (painted with water based spray paint on the foam before laminating). The surface was a compounded and polished Reichold gloss resin, the final step being polishing via rotary polisher and wool bonnet using surfboard polish #2. I felt like the smart thing to do might be to sand it a bit to help with adhesion of the sealer, but eventually I decided to just try it without any sanding or scuffing of the surface before applying the sealer. All I did was clean the surface with Isopropyl alcohol.
I applied the first coat top and bottom using those blue lint free shop paper towels. I just poured some sealer on the board, spread it quickly all around then used long straight passes nose to tail with firm pressure to remove excess and get a smooth even coat. I got a very smooth surface with only minor streaking. I wrapped around the rails and slightly onto the underside surface of the board with the applicator, which in my case left a visible messy line where you can see the border of where the sealer ends. This disappears when you do the other side, but sooner or later you are doing the last application, and If you want to avoid this issue, probably the best thing to do is not wrap around the entire rail onto the bottom surface but rather just apply the sealer only to the top half of the rail, right to the apex of the curve. This is not what I did, but I think the border where the sealer ends would be way less visible on the apex of the rail than it is on the surface of the board.
What did I learn:
Using those blue lint free shop towels folded over into quarters makes a pretty good applicator, resulting in minimal streaking. Using a microfiber cleaning cloth works pretty well too. Both seem to leave about the same amount of streaking, which is pretty minor.
Even three light coats of sealer did not hide the sand throughs. I’m fairly sure they are sealed, but they are still visible. Note that on this board I used water based spray paint directly on the foam before lamination, and the two main colors are a fairly dark green and a medium blue.
After one coat of sealer I tested how it would look by using a maroon scotch brite pad to scuff/buff it (by hand), but that dulled the surface, which is not what I wanted in this case.
It’s a major pain to remove any sealer not wanted like where you have drips or streaks left by whatever you use to apply the sealer. Where this happened I used rubbing compound #7 on a damp rag to essentially scratch away the unwanted thin film of sealer, and then reapply. The good news is that after reapplying the sealer over these areas where I used the rubbing compound, it looks nice and glossy again and I can barely tell that the area was scratched by the rubbing compound.
No problems with adhesion of the sealer onto the glossy surface, at least not yet. I have yet to surf the board, but based on how difficult it is to remove excess sealer where I had a few drips and streaks I feel like the sealer bonds very well to the glossy unsanded surface.
I’m pretty happy with how it turned out. Right now the finish is a fairly close approximation to that glossy mirror finish you get from traditional sanding, buffing and polishing of a gloss coat. From 10 feet away in natural light outside, I’m not sure I could tell the difference. However, in the garage with light hitting it from certain angles I can see streaks from the applicator I used, especially in the proximity of the rails. You can see this in a few of the photos.
That said, if I could figure out a way to buff this wet look sealer to an absolutely smooth surface without dulling the finish, that would be ideal. I’m tempted to try buffing it with the wool bonnet and surfboard polish #2, but before I do so, at the risk of causing me to have to go backwards a few steps, I figured I’d make this post and see if anyone has some thoughts, tips, or advice as to how to buff this sealer smooth or perhaps knows of an applicator that leaves no streaks, in which case I could just do another coat of sealer with that kind of applicator :)