Just about any new, unpainted surface, interior or exterior, should be
primed before applying a finish coat. Previously painted surfaces should
also be primed if the existing finish is deteriorated, after preparing the
surface - scraping, sanding, and washing. Prime can also be used as an
'undercoat' when painting over a darker color or tinted to match the new
paint color and used as a first coat in situations when you know you will
need two coats to cover. (I painted over a dark red with one coat of primer
and a single coat of the new light blue color).

As for when a primer is not needed - if the surface is in good shape, and
the new finish is close to the old, you can probably get away without
priming.

Remember - primers generally do not cover like the finish coat, so don't
paint yourself crazy trying to get good coverage with the primer. Just
ensure that it is applied evenly, without roller or brush marks - these are
hard to hide no matter how may finish coats you apply


"Robert11" wrote in message
news
Hello:

Not too sharp in the painting area.

Regarding Paint Primers:

Are there general rules of thumb for when, and where, paint primer should
be used before applying the regular paint ?
Interested in both interior and exterior.

Would the answers be different for oil vs latex paints ?

Guess I should also ask if there are times when it should not be utilized
?

Thanks,
Bob