ALTANA Pfund Cryptometer - Manual (Page 4)

then confirm visual hiding of the paint sample at
the average setting. The number of square feet of
surface area visually hidden by one gallon of paint
is quickly determined by reference to Table 1 on
Page 2. The corresponding thickness of wet paint
in mils (1 mil = 0.001 inch) can also be determined
from Table 1. For Example: If a No. 7 top plate with
a wedge constant of 0.007 results in an average
Cryptometer setting of 27mm, then the wet paint
will hide visually at the rate of 215 square feet per
gallon, and the wet film thickness will be 7.44 mils.
This target film thickness can be controlled by
checking it periodically with the Pfund Film Gauge
to assure uniform wet hiding.
DIRECTIONS FOR SELECTING TOP PLATES
A top plate is identified by a number from 1-9 that
is equal to the thickness, in mils, formed by the
wedge over the central line when the Cryptometer
is set at 1.000 inch = 1,000 mils = 25.4 millimeters.
The wedge constant is therefore numerically equal
to the slope of the top plate caused by the length
of its protruding pegs. These pegs can become
worn down by prolonged use over abrasive
pigments, or otherwise damaged. When ordering
extra top plates, be sure to specify the correct
wedge constant that is desired, and also the
model of Cryptometer with which it is to be used.
The three standard top plates are now identified
as follows:
No. 2 with Wedge Constant K = 0.002
No. 3.5 with Wedge Constant K = 0.0035
No. 7 with Wedge Constant K = 0.007
Other top plates with other wedge constants are
available on special order
Description
DIRECTIONS FOR BLACK-AND-WHITE CRYPTOMETER
This all-purpose model is applicable not only to
black and white paints, but to paints of all colors.
It is furnished with Top Plate No. 2 for darker
paints and Top Plate No. 7 for lighter paints. In
case of doubt, it is advisable to use the top plate
which results in a setting nearest to 25.4 mm. on
one of the scales. In using the Black-and-White
model with Top Plate No.2 for black or near-black
paints, it is important to use an intense, constant
and reproducible artificial source of illumination. A
200-watt lamp is recommended.
To obtain reproducible readings for colored paints
the following steps should be taken in order:
(1) Follow carefully the instructions given under
“General Remarks” on Page 1
(2) Place the Cryptometer so that the black field is to
the left, apply a small pool of paint at the dividing
line between the black and white fields, lay the top
plate on it so that the pegs are to the right, an
make 5 pairs of readings for “disappearance” and
“appearance.”
(3)
Reverse the Cryptometer so that the white field is
to the left, and proceed as before to make 5 pairs
of readings
(4) Average the 5 quadruple sets of readings –
disappearance and appearance over both black
and white fields – to obtain a practical mean
setting that can be confirmed for visual hiding
after resting the eyes
(5) Refer to Table 1, under the column heading for the
top plate used, to obtain the corresponding Wet
Hiding Power in square feet per gallon or square
meter per liter and also the corresponding Wet
Film Thickness in mils or thousandths of an inch
or microns.
Description
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