Re: [A/S] Re: Clearcoat + painting A/S Finish Durability

["Carol and Oliver Filippi" <ofilippi@xxxxxxxxxxxxx>]

Clear coatings are inherently  less durable than pigmented (paint) coatings.

The primary reason for this is that ultraviolet light penetrates the clear
coating and breaks it down from within.  To counteract this, clear coatings
often have UV filters to absorb the UV and reduce the damage.  It is my
understanding that these UV filters are sacrificial ingredients and are
"consumed" by the UV exposure and eventually lose their effectiveness.

Another possible reason is that the clear finish depends upon its cohesive
strength to hold together (how well it sticks to itself).  A pigmented
finish has finely ground pigment dispersed in the film, so it takes
advantage of the physical strength of the pigment and the adhesive (how well
the resins stick to something other than themselves)characteristics of the
coating.  [This is why concrete (Portland cement and aggregate) is more
durable and stronger than the Portland cement alone.]

In the last few years, auto makers have gone for color coat / clearcoat
finishes (a pigmented color topped with a clear finish to give added depth
and gloss.  If you look at these finishes after weathering, they not only
get dull, but the clear coat crazes (fine spider like cracks) and breaks
down, flakes or peels off and turns white. [Not unlike the clearcoat
failures we se on Airstreams] Polishing will not restore them.  A plain
pigmented finish, on the other hand,  will simply get dull, and can usually
be brought back with a compounding or polishing.  The clear coat failure
goes all the way through, whereas the pigmented failure is usually limited
to surface oxidation.

Oliver Filippi