Blisters on antifoul

[cmedsailor]

Last time I antifoul my boat (haven't lift since then) was March 2011. The boat is in the Med and I have used Nautix A4T hard antifoul. Early May and since then a few times I brushed the antifoul paint (it's hard paint so you can do it) with a "medium hard" brush to remove some dirt. Lately I have noticed, in places where I used the brush (both on hull and ludder) that there are lots of blisters on the antifoul paint. I broke a few with my nails and were simply blisters on the paint. Why is this happening? Could it be osmosis or is the life of my antifoul paint coming to its end?
Thanks

 

[little_roundtop]

When you break the blisters do they smell?

 

[cmedsailor]

When you break the blisters do they smell?

I will check during the weekend!