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VallelyJ 03-24-2012 11:25 PM

How to ID bottom paint
Is there a way to tell hard from soft (i.e. ablative) bottom paint when it's on the boat?
I have to touch up a few spots--the paint looks sound otherwise, but I read that you can paint new hard over old hard, but not over old soft.
Is there any sort of hardness test to tell which is which?
John V.
Alajuela 33

Minnewaska 03-25-2012 06:25 AM

Re: How to ID bottom paint
Ablative means that it will continually shed the outer most surface of the paint, revealing fresh unexposed paint to continue its job. Obviously, putting hard paint over it, would be shed off as well.

Paint compatibility is tricky. Not all hard can be painted over all hard, etc, etc. I take it that it was last painted by a prior owner. Any way to get in touch and ask? Paint manufacturers are pretty good at publishing what can be painted over what. It can be brand and formula specific, no totally safe rule of thumb.

If the current paint has worn down to where skips need touching up, you are probably in need of a full paint job, even if the rest looks intact. Consider stripping, so you know where you stand.

hellosailor 03-25-2012 11:59 AM

Re: How to ID bottom paint
As a guide but probably not a hard rule, if you can rub a white rag (t-shirt or towel) over the paint and it comes off on the cloth, that's soft paint and ablative. If you can't rub it off, that's hard paint.

If you want certainty, you probably have to strip the old paint, or just find something that's compatible "with everything" for your touchups.

VallelyJ 03-25-2012 05:20 PM

Re: How to ID bottom paint
Thanks for the replies.
The PO is unfortunately not accessible.
The white rag trick is what I was hoping for--some way to test the hardness. I think if that test indicates a hard paint, I'll touch up the bare spots with another hard paint, maybe the Copper Pro SCX that PS recommends, and see how it does after another season. The remaining old paint is sound enough that it ought to be ok till then, so I may be able to avoid stripping the whole hull.

Minnewaska 03-25-2012 05:53 PM

Re: How to ID bottom paint
Looking sound doesn't mean it still works, just that it still sticks. If it is worn through in places, I'm willing to bet you are wasting your time and money.

Fstbttms 03-25-2012 07:17 PM

Re: How to ID bottom paint

Originally Posted by VallelyJ (Post 850249)
I read that you can paint new hard over old hard, but not over old soft.

Not true. Most commonly used, copper-based anti fouling paints are compatible with one another, whether they are hard or ablative. Here is a good chart illustrating what can be used with what:

Minnewaska 03-25-2012 10:02 PM

Re: How to ID bottom paint
It's a crap shoot not knowing what you have. Here is a brand specific compatibility chart.

JimsCAL 03-25-2012 11:42 PM

Re: How to ID bottom paint
Sounds like your boat is "on the hard". Without knowing what you have on the bottom, you have to assume it is not a "multi-season" paint and thus a coat of paint is needed in any case. You don't want to launch and get into the season and find you have significant fouling and have to do a short haul to put some paint on.

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