Here you can learn about what is needed to apply a Gel Coat.
1. Prep the area removing all of the damaged gel coat Keep the repair as small as possible. Prep the damaged area with 220 grit sand paper. Sand down any rough edges. A Dremel tool or die grinder can also be used to prep the damaged area. Cracks must be ground out prior to applying patch paste.
2. Begin by wiping the area clean with a acetone. Mix 10-12 drops of catalyst with 1 ounce(half a jar) of Spectrum Color factory color matched Patch Paste®. Fill the damaged area with the smooth drag. A second application may be necessary. After patch paste is cured, 1-2 hours sand and buff to finish.
3. Mark the repair area with a grease pencil. This prevents over sanding. Sand the patch with a 220 grit sand paper. Sand only as much as necessary to remove the excess material and or the grease pencil's color. Keep the block or sander flat to prevent a wavy patch. Repeat process with 400 and 600 grit paper.
4. Buff the area with a mild compound to remove the 600-800 grit scratches. Repeat until the area is free of sanding scratches. Do not burn or over buff the area. This can discolor or remove all of the gel. Polish to a deep shine with a wax or glaze.
How to Repair Damaged Gelcoat (Video)
Learn how to repair damaged gelcoat, presented by Boating Magazine.
Okay. Well, here is the hole that we're going to repair today. This is a hole on the gelcoat, it was for an old screw hole that was holding something down. So as you can see, there's a little bit of staining from rust and whatnot around it. So, we're going to try to fix it and I'm going to take you step-by-step through the process and we will hope for the best outcome.
Okay. Now, here is the hole as it stands right now. We're going to grind it down a little bit. We're going to use a drill bit, a drill with a countersink bit just to grind it down just a little bit. I can't get in to it that way so I'm going to back off a little bit and here we go.
All right. So, we're just going to grind it down just a little, don't want to get too carried away with this. So, there you go. Ground the edges down a little bit. Try to get it flush with the surrounding surface and camphor the edges just a little bit. So, might get a little bit more grinding on this and then we're going to clean it up and mask in off.
Now we're going to clean up this with a little bit of acetone. We got a can of acetone and we got a rag and I've got some gloves on to protect my hands from the chemical. Basically, what we're going to do here is we're going to soak a little bit of acetone onto the rag and we're going to clean up the surface as best we can trying to get rid of any residual silicone or any kind of adhesive that might be inside the screw hole, that would prevent the gelcoat from adhering properly to this particular repair.
So, we clean it up as well as we can right now and I'm going to clean up a little bit more, and then we're going to come back here and tape off the hole and get it ready for applying the gelcoat.
All right, here we are again. This time we've taped off the area immediately surrounding the repair area and that is we make a little bit carried away with the masking tape. But the idea here is to protect any of the surrounding material, such as the stainless steel, the underlying gelcoat, or the starboard structure to the left there from any damage or any gelcoat for that matter that might occur while we're doing the repair. All right, now we're going to mix up the gelcoat and get it ready to apply to the repair area.
Here we have the main ingredients of our gelcoat repair. We have a mixing cup right here, we have the resin. In this case I'm using a paste or a gel resin. We have some whitening agent and this is the whitening agent here. It's just kind of a white creamy paste that you add to the gelcoat. And finally, we have the hardener or the catalyst that you add to the gelcoat once you've mixed up the color with the gelcoat the way you want it. All right, let's get started.
All right well, the first step is to take out a bit of the gelcoat. I'm using just a little popsicle stick here and I'm going to add it to the mixing cup. Now I'm probably going to mix up more that I'm going to need for this particular application, but better to have more than you need than not have enough.
Now, the next step is to add the whitening agent. You don't really need to add a lot of the whitening agent, about 20% of the volume of the gelcoat is what you're really looking for. And on this particular case, the whitening agent is a little runny so we didn't mix it up. So, there we go. We got a little bit of whitening agent in there, now we're going to mix that up.
Now that we've mixed up our color we've added a white pigment, and I'll say I had a just a hint of some black because the gelcoat in this repair is a little bit on the grey-white side, but not much. So, next step is to actually add the hardener which we have right here or the catalyst.
We're going to add about eight drops per teaspoon of gelcoat. So, we got about a teaspoon here, maybe a little bit more, so we're going to go a little bit heavy on the hardener. Probably add about 10 drops and it goes kind of like this: One, two, three, four, five, six, seven, eight, nine, ten drops. That's 10 drops right there.
And now the hardener. This is going to work with the gelcoat and it will create a chemical reaction that'll start to make it gel and then eventually get hard. But before that happens, we're going to go out and we're going to apply this to the repair area.
All right. So here we are with the gelcoat on the boat and we're going to make the repairs to the area. So, I've mixed up the catalyst and the gelcoat thoroughly, got to do that make sure you've mixed it up thoroughly. And here we go with our repair.
So, you're just going to kind of drip it in to this particular hole. The trick here is to make sure it gets deep inside and doesn't just sit on surface and create an air pocket. So, we're kind of shoving it down there a little bit, making sure that it gets down inside the repair area. So, we're going to put just a little bit more on here. We mixed up way more gelcoat than we needed but that's kind of part of the process.
By the way, if you have any other repairs, we can do those now although gelcoat's going to harden up here pretty quickly and we won't have a whole lot of working time--we can see it's starting to gel already, maybe about 10 minutes maximum working time on this. So try not to get too much gelcoat anywhere other than the actual repair area, though you want to make sure that that gets in there really good.
So there we go. But right now, I'm going to let it sit. I'm going to let it harden. Also, we don't want to get too much on there because then we'll have more sanding to do, so let's smooth that out a little bit. So there we go. There's our gelcoat repair. At this stage, we're going to let it harden and we're going to come back and we're going to start our sanding process.
All right. Here we are now with our gelcoat setup. Some people like to spray polyvinyl alcohol on here to let it dry. I prefer to just let it dry on its own and maybe a little tacky on the outside, but we're going to sand it down anyway. So what we got here is three grades of sandpaper. I got a fairly aggressive grade, this is a 320-grit. We got a 600-grit, and I've got an 800-grit, and I got a little bit of water here because this is wet/dry sandpaper, so I'm going to be wetting the sandpaper as I start sanding.
So, I will start with my fairly aggressive sandpaper first, and then we're going to work our way down to the finer sandpaper as we finish up the job.
We've taken the repair down about as far as we can. As you can see, we're starting to sand through some of the masking tape and that's not good, you don't want to be sanding areas that don't need to be sanded down. So, at this point, we're going to remove the masking tape and we'll see that the repair is still a little high, but it's down to the level of the masking tape at this point, so that's a sign that we need to be taking the tape off.
Here we are with the tape peeled away. You can see the immediate repair area. I've worked it down at this stage with 320-grit wet/dry sandpaper. This point, now I'm going to start going to work on it with the 600-grit. You'll notice I left a little bit of tape on the sides of objects immediately surrounding this repair. That's just so I don't inadvertently sand other areas that I don't want to sand. So, better get to work now with the 600-grit. This process is going to take about five minutes. Previous to this it's going to take another five to ten minutes to finish it up.
I'm working away on the repair with the 600-grit at this point. You'll see that I'm keeping the sandpaper fairly wet and confining my sanding just to the immediate area of the repair. Believe it or not, keeping the sandpaper wet actually improves the abrasive qualities of the paper. So, we're almost ready to go to our 800-grit.
We got it damn pretty close to the surface of the existing gelcoat. I have a little bit of a match issue here, the gelcoat doesn't match exactly but that's pretty normal with these kind of gelcoat repairs, shouldn't be a major issue. And I got a little trick, I'll show you a little bit later on to help resolve any coloring match issues.
All right, here we are. We're almost finished up here with this. We've used just a little bit of sanding with the 800-grit but we got it down to the level, and it's nice and smooth, same level as the surrounding gelcoat. So, you can say we have just a little bit of a coloring match issue. That is because the gelcoat sometimes turns a slightly different color when you add the catalyst to the hardener, but as I promised you, I'm going to show you a little trick that will be able to fix that just as soon as we get this all cleaned up.
Here we've got our repair pretty much cleaned up. You can see, this is the repair area right here. Once again, have a little bit of a coloring match issue but a solution I have in this particular case is, I found a paint that very, very closely matches the gelcoat on my boat. This particular case, it's a Rust-Oleum Appliance Epoxy, comes in a little bottle that's almost like a Wite-Out. But it is almost an exact match for the gelcoat on my boat so I'm going to show you. I'm going to apply it and then I'm going to show you how well the repair matches after that.
All right. Well, we are all done. Our repair is pretty nice, not bad, not bad. We have a nice color match with thanks to that little vial of Rust-Oleum paint that I have for appliances, it's a perfect match for the boat. So, that's how you do a gelcoat repair and this one turned out to suit my liking.