Boat Pox? Bumps (bubbles?) after stripping bottom paint

[NateD]

I used peel away to strip off the bottom paint this weekend (more on the whole process later). Once the paint was off, the hull looks like it is covered in many, many small bumps. Looking at pictures of "blisters" on the internet, these look too small. I haven't done much sanding yet, but it seems like they might disappear after sanding (or at least be greatly reduced). Anyone know what causes them? Are they blisters? Old paint that has lost it's pigment? Remnants of a clear or white barrier coat? Something else?

Long View, I did a little sanding in the spot.





Close up 1, still a little paint left around the bunk (that's the project for this weekend).





Close up 2.

[jpfx]

are you confident that this was not caused by the paint stripper?
what is the texture like?
from what I've read (I have no personal experience of this) you should be extremely careful with whatever remedial action you take that you do not contaminate the hull any deeper by sanding paint particles further into the surface.
I would probably consider, removal of bumps, fastidious cleaning of surface and application of an epoxy barrier coat if I had the task myself (and I might do as I plan to remove the complete hull paint job on mine this winter).
good luck

[mrb]

NateD

Looking at bottom couple pictures it looks as if you sanded through some of the bumps and blue color is showing. Or is the blue just residue from old paint you are taking off. If the blue is bellow the bumps then what you may have is an old barrier coat that was not put on smoothly. Have you found a layer that looks like it may be the original jell coat. Whether you are looking at blisters or not you should have areas that resemble the finish above water line. Like the strip just below the red line in picture 2.

If they are blisters ( after seeing the strip below red line in pic. 2 ,I am thinking you have an old barrier coat showing up)  you will probably want to sand them out and make proper fix.  

Regardless of what they are I would sand smooth, apply a good barrier coat them bottom paint.  Just me.  You will receive a lot of opinions and advice and in the end do what you feel good with.

Good luck, Melvin
PS If the bumps are harder to sand than the surrounding area they may be epoxy from a old barrier coating

one man's requirement may be another man's pain  

[NateD]

The blue is residual coloring from the bottom paint. Areas that I sand turn white. My plan is to sand the entire thing by hand with 100 grit to remove all residual coloring and bumps. Repair some deep scratches in the hull with gel coat. Repair with epoxy a couple spots on the keel where the gelcoat is completely gone down to the mat. Go over the hull again with 220 grit. Then a couple layers of epoxy bottom coating, finishing it in a white coat. She rarely spends more than a day in the water (and no more than a week), so I think I'll skip the bottom paint and leave it smooth and shiny.

[Craig Weis]

The bumps are similar to the ones on my 19 from boot stripe down. I believe these are from the optional factory non ablative anti barrier coating applied directly to the 'white' fiberglass as she came out of the mold. A second brown ablative bottom coat was applied prior to shipment.

Some 18 years later when it was decided to add a 'KEEL BOOT' a good hand sanding and scrubbing from boot down mostly removed the brown, but I never scratched into the 'bubbles' and never saw 'white' fiberglass. Then two coats of fresh Interlux Bottom Coat in blue was applied and waxed three times, the last two times the wax was not removed.
crazy skip.

[NateD]

The bumps are similar to the ones on my 19 from boot stripe down. I believe these are from the optional factory non ablative anti barrier coating applied directly to the 'white' fiberglass as she came out of the mold. A second brown ablative bottom coat was applied prior to shipment.

I bet that is what it was. There were a couple layers of blue bottom paint, then a layer of brown. I believe my boat sat in a slip in Florida for the first half of it's life, so I bet the first owner had Hutchins put on the factory non ablative barrier straight out of the gate.

[Steve Ullrich]

If the previous owner left her sitting in the ocean for years she could well have blisters.  They certainly look like blisters to me... If they are, the liquid inside is reportedly nasty, don't get it in your eyes.  I'd "pop" one to see if there is any liquid in it.  http://www.essortment.com/hobbies/hullblisterrep_sezg.htm

Steve

The bumps are similar to the ones on my 19 from boot stripe down. I believe these are from the optional factory non ablative anti barrier coating applied directly to the 'white' fiberglass as she came out of the mold. A second brown ablative bottom coat was applied prior to shipment.

I bet that is what it was. There were a couple layers of blue bottom paint, then a layer of brown. I believe my boat sat in a slip in Florida for the first half of it's life, so I bet the first owner had Hutchins put on the factory non ablative barrier straight out of the gate.

[Craig Weis]

I might add that although I purchased my CP-19 used from Yacht Works in Sister Bay, Wisconsin, I was the first fellow to put her in the water. The guy before me, Lloyd had lost his wife and traded the 19 in for a 'single hand' Sun Cat after fitting a Harkin '0-0' furler to my boat. I had a beer with Lloyd and his girlfriend at Sister Bay not too long ago. The cool thing was that Lloyd had kept every piece of paper that came with the boat and they are in my 'ship's papers'.
skip.