All things equal, soda or "media" blasting is a much better way to remove old anti-fouling
than sanding. Like any mechanical process, the desired end result depends a great deal on
the skill of the one performing the work. A good media blasting technician can coax all
the coatings off without damaging the underlying gel coat. Keep an eye on the process as
it begins. If the technician cuts through the gel coat more than once, pull the plug and
go to PLAN B. Always have a plan B.
If the gel coat is not perforated, you need not put any anti-osmotic coatings on the hull.
AMEL puts the anti-osmotic barrier coat BEHIND the gel coat while initially laminating the
fiberglass so, if the gel coat is not compromised, the anti-osmotics are still as
effective as they were originally. Just repair any areas where the gel coat gets cut and
you are good to go. Nothing wrong with the belt and braces(suspenders) approach of adding
more anti-osmosis coatings. However, they really are not necessary.
If you must employ any type of conventional machine sanding, watch the operator like a
hawk for the entire process as it is much more likely to result in damaged/perforated gel
coat compared to media blasting. Sand blasting has its own set of problems and should not
be used on fiberglass boat bottoms.
All the best,
Joel F. Potter
Joel F. Potter - Cruising Yacht Specialist
Amel's Sole Associate for the Americas
Phone: 1 (954) 462-5869 Fax: 1 (954) 462-3923