Difference between primer & regular paint?

  This is a serious question, not a troll or a trick, as I really don't
know the answer to this: what's the difference between primer and
"regular" paint?

First of all, some ground rules: I'm hoping to get answers from someone
who actually knows what they're talking about (any paint chemists out
there? or at least someone familiar with the inside of the paint
industry), rather than the usual speculation. Therefore, any answers
from "hallerb" or "ransley" will be politely ignored.

If someone forced me to explain the difference, my answer would be
something like, "Well, duuuh, I think primer has more solids or
something; or it's made to stick better. Yeah, that's the ticket--it's
stickier!" Obviously, no definitive understanding of really what primer
is and why we're 'spozed to use it.

Extra credit for answers to the following:

o Actual differences between oil-based primer (which I intuitively
consider to be better without really understanding why) and water-based
(latex, acrylic, etc.) primer.

o Are there any paints made today which can be considered "self-priming"
and which do not require primer?

The assumption is that we're talking about painting wood products here,
not speciality paints like for metal or other materials.

Your explanation of this matter, which is kind of like the eternal
debate over WD-40 (what it is and isn't and why it's no good for
anything) will be greatly appreciated.

 
I painted professionaly for about 15 years with a crew of 10 but im no
chemist and you dont want to hear what I know as fact.

 
I painted professionaly for about 15 years with a crew of 10 but im no
chemist and you dont want to hear what I know as fact.

-----------------------

Oh don't be so touchy.  He isn't being a jerk, he just doesn't know any
better.

  Ransley
I have been a painting contractor for over 40 years had crews of over 50
workers
the O P pissed me off too
ASK SHERWIN WILLIAM'S... snicker

I painted professionaly for about 15 years with a crew of 10 but im no
chemist and you dont want to hear what I know as fact.

 To be fair though.......   Just because you've applied 75,000 gallons of
paint doesn't necessairly mean you know the answer to the question.   I
could pump gas into cars for 55 years and still not know how the gasoline is
made.

just a thought.  Not trying to throw the gas (that i don't know how's made)
on the fire.


s