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All paints,
oil-based and latex, are made of three main components: 
They can also
contain other ingredients, which are known collectively as additives.
Binder is key
to paint formulation. The type and amount of binder affect everything
from stain resistance and gloss, to adhesion and crack resistance.
Waterborne paints
use several polymer types as binders, including:
- 100 percent
acrylic
- styrene-acrylic
- vinyl acrylic
(or "PVA" for polyvinyl acetate).
Oil paints use
a binder based on a drying oil such as linseed or soya, or some
other type of modified oil (in which case these paints are called
alkyds).
In general,
acrylic paints have better exterior durability than do oil-based or
alkyd paints. They have better colour retention, chalk resistance
and resistance to longer-term embrittlement and cracking.
Higher quality
acrylic paints have greater durability and other performance advantages
over lower quality latex paints -- mostly due to the type and amount
of acrylic binder used.
Quality paints
with 100 percent acrylic binders are especially durable. They adhere
to many different surfaces, such as:
- wood
- masonry
- aluminium
cladding
- vinyl
cladding
These all-acrylic
paints are more durable than other waterborne paints (with vinyl binders)
on fresh masonry surfaces. Other paints will show early colour loss
and film deterioration while 100 percent acrylic paints are
resistant to the effects of alkaline surfaces.
Pigments are
finely ground particles or powders which are dispersed in a paint
"Prime" pigments
provide colour and opacity (opaque coverage). The most common prime
pigment is titanium dioxide, which is white. It is used in acrylic
and oil-based paints.
"Extender" pigments
provide bulk to the paint at a low cost. These pigments impact on
properties like scrub resistance, stain resistance and chalk resistance.
Higher quality
paints will have higher levels of prime pigment than lower quality
paints. Also, better quality paints have less extender pigment in
relation to binder level. This makes them more chalk resistant on
exterior exposure, providing better colour retention and durability.
Though all paints will eventually fade, the rate of fading will
be much lower with better quality paints.
Additives are
performance-enhancing ingredients that are typically added to top
quality paints more than to ordinary paints.
Additives provide
desirable properties such as ease of application and the appearance
of the applied paint. Some also have protective qualities.
Mildewcides
are a category of additives used in exterior paints to keep mildew
in check so that the paint looks fresh attractive. These ingredients
are expensive, hence, higher levels are found in higher quality
paints.
Some other additives
used in acrylic paints are:
- dispersing
agents (to help the pigment remain evenly distributed throughout
the paint, rather than settling);
- preservatives
(to prevent spoilage of the paint during storage);
- materials
to minimise foaming during manufacturing and application).
The liquid portion
of the paint is either water (for acrylic paints) or solvent (for
oil-based or alkyd paints).
A
can of quality paint will contain a higher volume of solid material
(pigment and binder) than do ordinary paints. In the case of top
quality acrylic paints, that means more solids and less water.
Therefore, if
a top quality paint and an ordinary paint were applied at the same
spread rate, the top quality paint would dry to a thicker paint
film due to its higher solids content.
A top quality
paint will contain 35 to 45 percent volume solids, while an ordinary
paint will contain about 25 to 30 percent.
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