SPREADING RATES
The spreading rate of paint, is the area that a specific volume
of paint will cover at a specified film thickness.
There are two standard measurements used to describe the film thickness
of a coating, Mils and Microns. Microns are from the metric system
and are equal to 0.001 millimetres, and Mils are from the imperial
system and are equal to 0.001 inches. Since 25.4 millimetres equals
one inch then 25.4 Microns is equivalent to a Mil.
Spreading rate in Mils
Any liquid will cover 424 square feet per litre (ft2/L) when applied
at 1 mil wet. Therefore, a 100% volume solids material will cover
424 ft2/L when applied at 1 mil wet, and because it is 100% solids,
it will yield a 1 mil thick dry film. However if a coating is less
than 100% solids then the dry film thickness will be less since
the volatile portion of the volume will evaporate and leave the
film thus reducing the dried film volume or thickness. Suppose a
material has 42% volume/solids, you can calculate the square feet
that it will cover when a dry film thickness of 1.5 mils is required.
424 ft2/L x 0.42 = 178 ft2/L at 1 Mil thickness.
Since 1.5 mils dry is desired then: 178 = 119 ft2/L 1.5
A coating with %42 volume solids applied at 119 ft2/L or 450
ft2/Gal will produce a dry film that is 1.5 mils thick.
To calculate the wet mil thickness needed to get 1.5 mils dry:
1.5 mils = 3.6 mils .42
Spreading rate in Microns
Any liquid will cover 1000 square metres per litre at 1 micron
wet. Therefore, a 100% volume/solids material will cover 100m2/L
dry when applied at 1 micron wet, and because it is 100% solids
it will yield a 1 micron thick dry film. However if a coating is
less than 100% solids then the dry film thickness will be less since
the volatile portion of the volume will evaporate and leave the
film thus reducing the dried film volume or thickness. Suppose a
material has 42% volume/solids, you can calculate the square feet
that it will cover when a dry film thickness of 38.1 microns is
required.
1000 M2/L x .42 = 420 M2/L at 1 micron thickness.
Since 38.1 microns dry is desired then: 420 M2/L = 11.0 M2/L
38.1
A coating with %42 volume solids applied at 11.0 M2/L or 41.6
M2/Gal will produce a dry film that is 38.1 microns thick.
|
