Scratches on swim platform

[STB]

STB. Care to share why you need to thin the gelcoat and even the video is unclear as to what thinness compared to the as is can of gelcoat. Use a syringe, then pour styrene (amount of each).

Can you compare to a liquid consistency we can relate to? Why is it not thinned to start with?

Hey Steve,

Out of the can, the viscosity is appropriate for application by brush or roller. It doesn't really flow out ridges to flat. And, it won't spray well, if at all. It mostly splatters.

Out of the can is fine, even beneficial, for a roller or brush because the goal is to over apply and then sand down and polish. With it more viscous, it stays put better.

To get a visual, see how the unthinned product, while very much a flowing liquid, stands up in a small puddle in this video, which is a companion to the other one I posted:

The thickness is thicker than whole milk but thinner than honey. Maybe as thick as a table syrup? It may depend a little on brand and temperature.

Even for paints like Perfection or Awlgrip, they get thinned differently (different thinner) for spraying than for brushing. The film thickness per coat and amout of flow expected is very different between the two methods of application.

It is hard to say how much I thin the gelcoat. 10% would be a good guess. I usually thin it until the viscosity seems to me to be a hair more than spray paint, then try it, then adjust in tiny increments until I like the flow.

I wish I could give you a good scientific answer, but I don't do this super super frequently and each time seems to be a little different w.r.t. how much gelcoat, how much pigment, how much thinner, the air temperature, the humidity, horizontal vs vertical, etc.

I mix it for color first, and place some directly on the boat to check, immediately wiping it off with acetone. Then, when I like the color, I thin and test spray onto cardboard. If I need to thin more, I do. One can make.more than needed and, if over thinned, just go back to the less thinned portion.

I always start by mixing more gelcoat than I'll put into the sprayer bottle. That way I can add some back if I over pigment. I have also added some back to thicken the coat for more coverage. But I then needed to deal with small amounts of pigment.

The thing I learned is that too much light is as bad as too little light for color matching. I really like indirect sunlight. Darkness poses an obvious problem. But on super bright days when the sun is right on the repair, I can't tell the difference between the shades very well. They all looks bright white. I end up seeing the repair later in different light and realizing give got to sand a bit and try again for the perfect color match. Obviously something can be used to variously shade the repair to check color originally. But I haven't been so good at that.

 

[STB]

If not using the smaller patch, I would need to buy a can of "one step finish" and some tubes of tint to use the sprayer. I wonder if a smaller can is available.

What tint are needed for different "grey scales" of white?

View attachment 154315View attachment 154316

Hey Paulga,

They have kits that have a bunch of pigments. I've always used one of those. Total Boat or others may have more options w.r.t. size, possibly even in premixed colors that will get you close.

 

[STB]

Hey Steve,

Out of the can, the viscosity is appropriate for application by brush or roller. It doesn't really flow out ridges to flat. And, it won't spray well, if at all. It mostly splatters.

Out of the can is fine, even beneficial, for a roller or brush because the goal is to over apply and then sand down and polish. With it more viscous, it stays put better.

To get a visual, see how the unthinned product, while very much a flowing liquid, stands up in a small puddle in this video, which is a companion to the other one I posted:

The thickness is thicker than whole milk but thinner than honey. Maybe as thick as a table syrup? It may depend a little on brand and temperature.

Even for paints like Perfection or Awlgrip, they get thinned differently (different thinner) for spraying than for brushing. The film thickness per coat and amout of flow expected is very different between the two methods of application.

It is hard to say how much I thin the gelcoat. 10% would be a good guess. I usually thin it until the viscosity seems to me to be a hair more than spray paint, then try it, then adjust in tiny increments until I like the flow.

I wish I could give you a good scientific answer, but I don't do this super super frequently and each time seems to be a little different w.r.t. how much gelcoat, how much pigment, how much thinner, the air temperature, the humidity, horizontal vs vertical, etc.

I mix it for color first, and place some directly on the boat to check, immediately wiping it off with acetone. Then, when I like the color, I thin and test spray onto cardboard. If I need to thin more, I do. One can make.more than needed and, if over thinned, just go back to the less thinned portion.

I always start by mixing more gelcoat than I'll put into the sprayer bottle. That way I can add some back if I over pigment. I have also added some back to thicken the coat for more coverage. But I then needed to deal with small amounts of pigment.

The thing I learned is that too much light is as bad as too little light for color matching. I really like indirect sunlight. Darkness poses an obvious problem. But on super bright days when the sun is right on the repair, I can't tell the difference between the shades very well. They all looks bright white. I end up seeing the repair later in different light and realizing give got to sand a bit and try again for the perfect color match. Obviously something can be used to variously shade the repair to check color originally. But I haven't been so good at that.

Looking at Total Boat's product, their instructions read, "Thin TotalBoat Gelcoat with styrene, only as needed (up to 15%, adding more can affect the color of the cured gelcoat)."

TotalBoat Gelcoat With or Without Wax | Marine Gelcoats

TotalBoat ISO/NPG neutral and white marine gelcoats compatible with coloring agents. Gelcoat available with and without wax for boat building and repairs.

www.totalboat.com

 

[SteveK]

Thanks @STB

 

[STB]

Hey Paulga,

They have kits that have a bunch of pigments. I've always used one of those. Total Boat or others may have more options w.r.t. size, possibly even in premixed colors that will get you close.

Hi Paulga,

I guess I can add that I've always made the most use of white, black, red, and yellow.

 

[paulga]

Hey Paulga,

They have kits that have a bunch of pigments. I've always used one of those. Total Boat or others may have more options w.r.t. size, possibly even in premixed colors that will get you close.

I saw this repair kit yesterday. is this kit what you mentioned? is it also applied using the same Preval sprayer?

 

[STB]

For what it is, that's as good a kit as any for doing it without a sprayer -- which is a perfectly viable option. I suspect you'd want more than the 1oz and also want reducer if you were to spray. They do sell a 4oz version.

The thing that I dont like about that kit -- and I'm sure is the source of most of the negative reviews it has (among many good reviews) is that it is an unwaxed gelcoat and doesnt include any PVA.

Unwaxed gelcoat is said to cure only in the absence of air (I think it actually has to do with off gasing certain important chemical(s) that exist in minute quantities, e.g. the catalyst(s), vs exposing to air, but same thing in practice). So it has to be sealed off completely or won't cure. This can be accomplished by covering the repair with a film (the included release film or wax paper, etc), ensuring that the are absolutely no bubbles and the repair is totally sealed. Or it can be accomplished by spraying on a sealant, most commonly PVA, which is available in tiny pump spray bottles.

I like PVA much better. It doesn't mess up my repair. When I used release sheets, I always feel like I need to make the repair thicker and wider to be able to squish it down while getting the air out.

In general, I use unwaxed gelcoat and PVA for deep fills and then waxed gelcoat and a sprayer for the top coat.

I don't know if I've ever been in that day, but if I didn't have any waxed gelcoat for the finish coats, I'd probably just spray unwaxed gelcoat and then use PVA.

I'd have to have a very large repair before I'd want to use sheets instead of PVA. Sheets have the advantage of being faster to remove from a large surface when done. PVA has to be cleaned off with (warm is better) water and a rag.

There are also wax additives and other release agent additives that can be added to vanilla gelcoat, but they can be harder to dose in small quantities, which is why I'd like to buy it that way or use PVA over the top.

With PVA, you want to apply it fairly promptly before the reducer evaporates out to any significant extent. If that happens the cross linking doesn't happen fully and it will never cure, remaining soft to sticky forever. People seem to do repairs then try to seal them with film or PVA or whatever hours later -- and then get shocked that it didn't work.

Why not try this...buy that kit and some PVA (poly vinyl alcohol, not wood glue). Do the repair by hand without a sprayer. You'll be fine, even if it takes a couple of tweaks to make it right.

Next time, add a sprayer and some more reducer to your toolbox. You'll already have the coloring agents. Try your hand at spraying. You'll have already practiced the fill and finish.

Doing it this way you can do your whole repair with that kit, a cheap thing of PVA, and the sanding and polishing supplies.

Don't make this a bigger deal than it is. I know it can all be intimidating with so many options and so much chemistry.

But once you get started, you'll practically be done! Really!