I removed all the bottom paint, but...

[SVTatia]

The first coat of ablative anti fouling on the gel coat is blue.
I sanded all the paint off down to the gel coat, but its not white as it should be - a blue haze is etched into the gel coat and I can't remove it. I tried different grits sandpaper and not matter how much I sand I cannot get it to be white. If I try too hard I remove the gel coat down to the fiberglass.
I also tried acetone, although the rag came out with a little blue, it did not remove anything.
Not sure how to proceed, or whether or not the Interprotect 2000 will stick to a etched gelcoat.
The boat is 47 years old and I have no blisters, but since the hull is very dry, this is a great chance to apply a barrier coat.
So here is a question to the experts, can I just wipe the hull with acetone and apply the barrier coat? Would I need a tie coat?

[UNCIVILIZED]

Have you tried a light scrub in a small section, with just plain old water & a scotchbrite pad? It's going to sound crazy, but the blue haze which you're seeing might be mold release. Which, nominally, is water soluble. And when applied, dries to a light blue haze, or many of them do anyway. Thus my question/line of thinking.

Also, you could try doing a good solvent wipe on a section, as you're suggesting. Then apply some bottom paint, allow it to dry, & do the peel test with tape. PS has plenty of good examples.
Ditto on a small section scrubbed with water & the Scotchbrite pad, as described above.

That, & it wouldn't hurt to contact the paint manufacturer(s) with your conundrum.

[Hudson Force]

I'm interested in the responses here. My own boat is 42 years old and I've been maintaining a blister free bottom for 31 of those years. Well, not actually blister free,- I've had seven or eight averaging around nickel size.

At my last bottom job I had some sheets of accumulated paint shear off down to the gel coat. We've removed a lot of old paint in the past, but not had this much delamination of old paint before.

I painted as I have before on likely as many as 20 occasions.

I don't have any specific questions beyond those posted by the OP, but I'm interested in all the "older bottoms" and individual accounts.

[SVTatia]

My intention is to apply Interprotect 2000 then antifouling.

I power washed and scrubbed the hull - it removed all the dust, but the blue haze is still there. If you wipe your hand on it, it comes out clean.

[SVTatia]

The gel coat seems to be in good shape, it has spider cracks at some places, but no blisters after all these years. I could just put 2 or 3 coats of bottom paint and move on, but the reason I plan on applying the barrier coat is that this is a unique opportunity - a dry hull because the boat has been out of the water for 4 years.

[Johnathon123]

Try a commercial Mould Release cleaner from a boat builder's supplier. You might need to search around a bit to find what it is you have available but if it is "the mould release agent" that should get it off.

Having said that, if it hasn't caused you an issue for 20 odd years, cover it up and enjoy the next 20?? Just a suggestion.
Good Luck

[SVTatia]

Originally Posted by Johnathon123

Try a commercial Mould Release cleaner from a boat builder's supplier. You might need to search around a bit to find what it is you have available but if it is "the mould release agent" that should get it off.

Thanks for the responses.

I am not sure if the blue "hue" is from a mold release - bottom paint would adhere if it was.

Starting to think that if the bottom is good after 47 years, should I really apply a barrier coat?

[Reefmagnet]

I've used general purpose paint thinner to good effect. You do need to use a good breathing filter and proper gloves. We stripped off the antifoul from a 27 footer using about 3 or 4 gallons using (lots of!) well soaked rags. Messy, but a lot cleaner than sanding without vacuum extraction.

[a64pilot]

Originally Posted by SVTatia

Starting to think that if the bottom is good after 47 years, should I really apply a barrier coat?

I think you have hit on it right there, your going to try fixing something that isn't broken, maybe. I believe if it really is blister free, why change? I mean after 47 years I assume if it was going to blister, it would have by now?
But if I understand blisters, given enough time on the hard, they eventually disappear, big ones I assume will show up as a delam with a tap test, but won't be visible as they aren't a blister. Did you see this boat when she first came out of the water or did you buy her recently?
Course I could be wrong, I have a limited understanding of the things myself.

[minaret]

The blue haze is almost certainly skip sand. This is an acid etch often applied at commission instead of sanding. It often leads to bottom paint failure down the road. Bottom paint flaking right down to gel with a blue or green film on it is a sure sign of skip sand. It's very common.


It's fine to apply 2000 over it, as long as you have a nice profile for tooth and only traces of skip sand remain.

I would recommend applying 2000, even if you have no blisters after 40 years. Several reasons:

The added thickness of coating will help fill in your grit profile and any other imperfections.


Even if you only do two coats, instead of the usual four, it will help fill in the surface.


It will provide an excellent tie coat if you apply AF by chemical bond. This will give you a base layer of bottom paint with excellent adhesion. Much much better than simply rolling AF on sanded gel.

Again, only two coats are needed if you are looking for tie coat rather than barrier.

[SVTatia]

Originally Posted by Reefmagnet

I've used general purpose paint thinner to good effect...

That is one thing I did not try, I will give it a shot.

Originally Posted by a64pilot

I think you have hit on it right there, your going to try fixing something that isn't broken, maybe. I believe if it really is blister free, why change? I mean after 47 years I assume if it was going to blister, it would have by now?
But if I understand blisters, given enough time on the hard, they eventually disappear, big ones I assume will show up as a delam with a tap test, but won't be visible as they aren't a blister. Did you see this boat when she first came out of the water or did you buy her recently?
Course I could be wrong, I have a limited understanding of the things myself.

I saw the boat a couple of months after haul out and the bottom did not have any blisters. When sanding I have some places where I removed the gel coat, but these will be filled and faired with epoxy.

Originally Posted by minaret

The blue haze is almost certainly skip sand. This is an acid etch often applied at commission instead of sanding. It often leads to bottom paint failure down the road. Bottom paint flaking right down to gel with a blue or green film on it is a sure sign of skip sand. It's very common.


It's fine to apply 2000 over it, as long as you have a nice profile for tooth and only traces of skip sand remain.

I would recommend applying 2000, even if you have no blisters after 40 years. Several reasons:

The added thickness of coating will help fill in your grit profile and any other imperfections.


Even if you only do two coats, instead of the usual four, it will help fill in the surface.


It will provide an excellent tie coat if you apply AF by chemical bond. This will give you a base layer of bottom paint with excellent adhesion. Much much better than simply rolling AF on sanded gel.

Again, only two coats are needed if you are looking for tie coat rather than barrier.

Good point, I never thought of the skip sand. Did they do that even back in 67?
The first coat of anti fouling is blue, that is why I thought I "pushed" its particles into the gel coat when sanding with 40 grit.

I have a good base for the IE 2000 to bite into as the surface is kind of rough due to the 40 grit.
I do follow your reasoning for the barrier coat, and as mentioned before, with a very dry hull, this is perhaps the only chance I'll ever have to do it.

After fairing and sanding the dings I created, I'll cleanup as much as I can and apply 2 or 3 coats of IE 2000. And yes, will go for the chemical bond for the AF.

Thank you very much, I definitely feel better...

[Cheechako]

isn't the blue haze just bottom paint in the surface of the gel coat? just sand the bottom rough and apply the epoxy.

[minaret]

Originally Posted by SVTatia

That is one thing I did not try, I will give it a shot.



I saw the boat a couple of months after haul out and the bottom did not have any blisters. When sanding I have some places where I removed the gel coat, but these will be filled and faired with epoxy.



Good point, I never thought of the skip sand. Did they do that even back in 67?
The first coat of anti fouling is blue, that is why I thought I "pushed" its particles into the gel coat when sanding with 40 grit.

I have a good base for the IE 2000 to bite into as the surface is kind of rough due to the 40 grit.
I do follow your reasoning for the barrier coat, and as mentioned before, with a very dry hull, this is perhaps the only chance I'll ever have to do it.

After fairing and sanding the dings I created, I'll cleanup as much as I can and apply 2 or 3 coats of IE 2000. And yes, will go for the chemical bond for the AF.

Thank you very much, I definitely feel better...

You may be right, '67 is probably pre skip sand. If it's just leftover AF, your 202 wipe should remove it. You are using 202, right?

[Wrong]

I wouldn't worry too much about the blue color in the gel coat provided you've followed instructions for prepping the gel coat. Dewaxing is the main objective. Sand only if the directions say so, AFTER dewaxing.

[Scrimshaw4]

You may be looking at a previous barrier coat.