Barnacle Glue removal ideas?

[relamb]

Anyone have advice on removing the glue rings that barnacles leave after scraping?  Something that can dissolve them?
MY 1988 CP27 came with some flaking bottom paint over what appears to be a gray epoxy barrier coat.  I left it in saltwater over the winter and had it scraped monthly by a diver.  Where the old bottom paint was intact, everything is fine, no growth.  Where it flaked off, barnacles grew on the barrier coat.
Those have all been scraped off, and I'm ready to sand for bottom paint.  However, I don't want to sand through the epoxy and really can't find any other way to get that ring of barnacle glue off other than sanding.

I guess plan B would be to sand them off and then get a quart of epoxy and touch up those areas.  There's no reason I can't touch up spots on the epoxy without doing the whole thing, I presume.
Opinions?

[MacGyver]

I highly suggest coating the boat with one coat of 2000 after you sand it, maybe even 2 depending on how bad you sand the boat. This way you know you are good on the thickness of the barrier coat.

I typically tell customers this because without the barrier coat, the chance of blisters is going to go up. My rep doesnt normally suggest touch ups, in stead, he tells me to touch those areas up, then also follow up after a few touch up coats with a full over coat because chances are you have sanded thin spots you dont even know about.

Mac

[MacGyver]

Oh, and I also turn out 2000 (barrier coat) jobs with extra coats on corners, rounds, edges, and places likely to hit bottom first as a extra layer of protection.
Once a small spot of broken gelcoat finds water, the blister effect will radiate out from that area........ like a chink in the armor of the bottom, and that is what you are fighting against to begin with.

Mac

[brackish]

When I had boats in the salt water I often wondered about that, but never tried anything other than sanding.  However, the ring that is left is just part of the shell and it is a material that I'm sure is way over on the base side of the PH scale, so maybe an acid will dissolve.  You could start with vinegar and move on to more aggressive acids until either you or the barnacle ring flinch.

[relamb]

As I read elsewhere on the net, acid dissolves the barnacle shell just fine.  I put on a little full strength muratic acid on a few places I'd scraped, and it fizzed up and dissolved the remaining bit of shell immediately.  About like putting baking soda in vinegar.  However, the glue ring was a different story.  It's supposedly made of protein chains that aren't water soluable and works similar to the way blood clots.  The acid did seem to soften it a little so I could scrape scrape scrape and get it off (one barnacle at a time).
Not worth the effort, so it's back to sanding like the rest of the world.
I've decided to go ahead and sand the whole hull down to the barrier coat, and then put on a new barrier coat with Interlux 2000e.
...while I still have access to college kid labor for another week.

[CaptRon28]

I've had pretty good luck with Marykate "On and Off" bottom cleaner. It's got an acid base plus other chemicals and cleaners in there. Comes as a liquid and gel. The gel tends to work better on vertical and bottom surfaces when you're going against gravity.