MIL-HDBK-1110
The beads should be relatively uniformly spread across and along
the marking. At least 25 beads should be found in every square
inch, to obtain desired level of retroreflectivity.
l) Procedure 12: Wet Film Thickness of Stripes. Wet
film thickness can easily be determined using the procedure of
ASTM D 1212, Measurement of Wet Film Thickness of Organic
Coatings. A metal or plastic gage with calibrated notches cut
into each of four faces is used for this purpose. The face
calibrated for the desired wet film thickness is pushed squarely
into a freshly painted surface and withdrawn. The wet film
thickness of the marking is equal to the depth of the deepest
notch with paint on it. A sample of wet paint without beads must
be applied to a rigid test panel by the striping machine in a
test run. It is best made on roofing paper or other disposable
material to avoid contamination of a pavement. Obviously, a
series of plates secured across the width of 3-foot-wide stripes
must be used for each test run to determine localized application
rates.
m) Procedure 13: Dry Film Thickness of Paint Film.
The dry film thickness of a paint film can be estimated from the
wet film thickness by the relationship:
Dry Film
Thickness = Wet Film Thickness x Percent Solids by Volume
100
Dry film thickness of paint applications can be determined quite
precisely using a magnetic gage as described in ASTM D 1186,
Nondestructive Measurement of Dry Film Thickness of Nonmagnetic
Coatings Applied to a Ferrous Base. A ferrous plate is coated
with marking paint by the striping machine but no beads are
applied. The paint is allowed to cure completely before its dry
film thickness is determined by magnetic gage. Again, a series
of test plates must be used on runway stripes to determine
thicknesses across the stripe. Tin-plated steel panels used in
paint elongation testing by ASTM D 522, Mandrel Bend Test of
Attached Organic Coatings are convenient to use for this purpose.
n) Procedure 14: Spreading Rate of Paint. After the
wet film thickness of a marking has been made, as described
above, the spreading rate of the paint can be estimated by the
relationship:
Spreading Rate of Wet Paint
in Square Feet/Gallon
=
1600
Wet Film Thickness in Mils
70
Previous Page
