If anyone is interested in learning more about latex paint, an excellent
resource is the website of the Paint Quality Institute:
'Painting information and resources for home interiors and exteriors -
Paint Quality Institute' (http://www.paintquality.com )
The Paint Quality Institute was established by the Rohm & Haas Company
who were the largest manufacturer of acrylic resins used to make latex
paints, acrylic floor finishes, grout & stone sealers and nail polish
for the ladies in North America until they got bought out by Dow in
2009. Dow has chosen to continue funding the Paint Quality Institute,
and to expand that web site. The original purpose of the Paint Quality
Institute was to educate paint specifiers (like architects), painting
professionals and consumers ( which I presume means people that drink
paint) on the benefits of consuming better quality latex paints, so it
has quite a bit of technical information in it. Unfortunately, I don't
know of a similar resource for oil based paints (although you can learn
lots about them at the PQI website, too).
The technology of acrylic paint is very similar to the technology of
acrylic floor finishes, and since I have to maintain both in my
building, it was important to me to learn this stuff, so I've spent
quite a bit of time on the PQI web site. I like to think I know a
little bit about latex paints now, and there's lotsa stuff in this
thread that needs to be clarified or the newbies in here might get
For simplicity, I broke this post into separate topics:
First off, here is my painting tip:
Instead of using a wire brush to clean hardened paint out of the
brush AFTER painting, consider soaking your brush in water (or mineral
spirits if using oil based paint) and shaking out the excess thinner
immediately BEFORE starting to paint. And, if you're painting for a
long time, use an eye dropper (that you can buy at any drug store) to
periodically add a drop or two of thinner to your brush (near the
ferrule) while you paint.
That's cuz those hardened pieces your're cleaning out of the
bristles are caused by the paint working it's way up the bristles of
your brush and drying there while you were painting. By wetting the
brush with thinner first, the air spaces high up in the brush get filled
with thinner, and any paint that works it's way up there will just be
diluted by the thinner, and won't dry up. So, you won't have to deal
with little pieces of hardened paint to begin with. And, it's that
process of paint drying inside the brush that causes brushes to go out
of shape, so preventing that from happening keeps your brushes in good
condition. (watch out when you first start painting with a wet brush
cuz there may still be too much water in your brush, and the paint in
your brush could be runny)
You should know that if the latex paint above your shower is peeling,
it's probably NOT because of insufficient prep work by the previous
painter. Paint peeling on the ceiling above a shower is most often
caused by using a "budget" priced paint where you need a better quality
In North America, most latex house paints are made of one of two
different kinds of plastics:
1. polyvinyl acetate (commonly called "PVA" or in paint speak "vinyl
acrylic" resins): which is used in general purpose primers and "budget
priced" interior latex paints. PVA is the same plastic that white wood
glue is made of.
2. polymethyl methacrylate (commonly called "PMMA" or in paint speak
"100% Acrylic" resins) which are used in better quality interior latex
paints, most exterior latex paints and primers for fresh concrete. PMMA
is the same plastic that Plexiglas is made of.
The problem is that most homeowners don't know very much about paint, so
they often buy inexpensive "budget" priced paint and use it everywhere,
including in their bathrooms. And, the PVA paint they use doesn't have
good enough resistance to moisture to stand up in a wet and humid
environment like a bathroom, especially on the ceiling above a shower
where the paint gets wet at least once per day.
In this case the advice not to buy cheap really applies. By buying a
better quality paint, the binder resin in the paint will be made from
that PMMA plastic which is very much more resistant to moisture.
And, if it wuz me, I would buy a latex paint specifically made for
bathrooms where the binder resin was specifically chosen because of it's
high resistance to moisture.
If the paint is peeling only where the moisture and humidity in your
bathroom would be highest, it's not a matter of insufficient preparation
prior to painting; it's a matter of using the wrong latex paint. This
is a common paint problem that most often misdiagnosed as insufficient
Go ahead and use a paint roller sleeve on your siding. I painted the
front and back of my father's commercial building with latex paint using
a paint roller years ago and never had any problems with that paint job.
I think the only reason people tend to use brushes on the outside of
there house is because a paint tray isn't as practical as a can when
you're painting from a ladder.
Someone said to pour off some paint into a small container and paint
from the container rather than the can...
..and that's because "oxygen is the enemy of paint".
Someone else said that if you have to stop painting for some reason,
wrap the brush and roller in plastic or foil and stick them in the
freezer. (I'd add that if you're using an oil based paint, wrap the
paint tray in a bigger plastic bag and put it in the fridge or freezer
Both of those statements are good advice if we're talking about oil
based paint, but they don't apply if we're talking about painting with
In oil based paints, oxygen will be absorbed into the paint as long as
the can is open. That oxygen chemically reacts with the oil or alkyd
resins to cause the paint to transform from a liquid into a solid. So,
the sooner you seal up your oil based paint can after pouring off as
much as you need, the less oxygen will be absorbed into the paint
remaining in the can and the less of a solid film will form on your
paint while it's in storage. (Pour off a generous amount since it's
better to put more paint on than to throw a bigger hunk of dried oil
based paint film in the garbage.) (If anyone is interested in that
chemical reaction with oxygen, ask and I'll post a link that explains
Since it's a chemical reaction that transforms oil based coatings into
solid films, cooling an oil based paint will slow that reaction down
immensely, so oil based coatings won't "dry" if they're cold. You can
paint a fence in a North Dakota blizzard with oil based paint, and the
paint will stay tacky until spring, when it will "dry" normally once the
warm weather returns.
However, normal latex paints form a film through a completely different
process called "coalescence" which doesn't involve any chemical
reactions, so I don't see any advantage in putting the latex paint in a
cold place. (If anyone is interested in how coalescence works, ask and
I'll post a link that explains it.)
(Latex floor paints do have a chemical reaction cuz they use something
called a "crosslinking acrylic resin", but that chemical reaction
happens in the days and weeks after that "freshly painted" smell
dissipates from the room or house.)
So, if you're painting with a latex paint and you have to stop for some
reason, just wrap the paint roller sleeve and paint brush in plastic
bags, and maybe wrap the paint roller tray in a bigger plastic bag, and
that's really all you need to do to prevent sufficient water evaporating
from the paint to cause it to "dry" while you're gone. If anyone sees
any benefit in cooling latex paint, I'd like to know what they're seeing
that I'm not.
Also, exposure to oxygen doesn't affect latex paints like it does oil
based paints, so there's no real benefit to pouring off as much latex
paint than you think you'll need and sealing up the can asap.
Someone suggested spraying your hands with Pam and putting cling wrap on
your glasses to protect them from paint spatter.
People should know that if you pay more for a better latex paint, you
won't have any paint spatter.
When I paint the walls and ceilings in apartments with Pratt & Lambert
Accolade Velvet or
Accolade Satin (at $50+ $Cdn per gallon), I don't even bother with drop
cloths to protect the carpeting in the suite cuz there simply isn't any
spatter. There might be the odd drop fall off the roller sleeve onto
the carpet, so I keep a spray bottle full of water and wet/dry ShopVac
style vaccuum cleaner handy to deal with those. But, when you figure
that you only paint once every 10 years at most, and you're saving most
of the cost by doing the work yourself, paying more for better paint to
eliminate the hassle of covering up everything isn't unreasonable.
Hope this helps someone somehow some day. Obviously, I'm not really