another gelcoat story

On Aug 25, 10:24 am, JJ Sinclair wrote:
Brad, I wouldn't brush on the primer, half your sanding will be to
just remove the brush marks. You can get a cheap gun and compressor
for this. It is usually best to use the primer that is recommended by
the paint you are using, but most are gray in color and this will
start to show through if (when) you get a little to heavy handed with
the wet sanding during the finishing process. That is why I use PCL
Polyprimer, because it is pure white and believe me white is the way
to go. You do need good ventilation any time your spraying anything,
not only to prevent trapping unwanted by-products in the paint, but
you don't want to be trapping any of this stuff in your lungs, either!
That is REALLY true when using uretahne, we had a mechanic here who
recovered a Cub in the dead of winter with propane heaters running
inside the shop. He didn't want to ventilate because he would lose all
his heat. Then he sprayed urethane in the same environment (probably
with just a dust mask)........................anyway, he is no longer
with us!
From personal experience, I was spraying uerthane one evening and
started to lose my peripheral vision, then I tightened up the mask and
got it back! Scary stuff, I could have passed out, alone inside a
paint booth full of stuff that can kill you. I use a resporator now,
not too expensive, $300'ish from Spruce and Specialty.
Oh, my how I have carried on and we haven't even touched on the
biggest proplem you will face. Pumping water droplets out of your
spray gun. Got to go wet sand yesterdays paint.............
JJ

My $0.02 on iso-cyanates and urethane paint:

Back around 1990 I painted a ship with Deltron Acrylic Urethane (PPG).
The results were great... However, I will not be doing that again.
Urethanes are simply too toxic for this amateur. Iso-cyanates are
incredibly bad news. How bad? To give an idea: I walked back into my
"booth" without protection about an hour after spraying the fill coat
(K-201 iirc) on one wing and almost instantly had bronchial
constriction and a really nasty head buzz. No more than 60 seconds
exposure an hour after spraying.... Scared the hell out of me. If
you must do this... at least be aware of who is down wind and how
far. If you decide to cheap out and forge ahead with a carbon filter
mask instead of a proper air-supply system, change the filters
frequently and don't wait for odor to become noticeable through the
mask, cause you'll be sorry. Furthermore, wear the mask any -- I mean
*any* -- time the paint is open including mixing.

Take the warnings seriously.

Today's mad hatter is more likely to be an auto body guy. Doubt me?
Go hang at the local body shop and see what you see. There's no way
to do this stuff with zero exposure.