FED-STD-141 Paint, Varnish, Lacquer And Related Materials: Methods Of Inspection, Sampling And TestingThis standard elaborates the methods used to determine the physical and chemical properties of paint, varnish, lacquer, and related materials. The purpose of this standard is to establish standardized testing methodologies and to eliminate unnecessary or undesirable variations in test results when evaluating a product??s adherence to specification requirements. If any variation or modification of the methods established in this standard is required by any specification, the procedures listed in the specification will take precedence. Any conflict between this standard and any particular specification will be resolved in favor of the specification.

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METHOD 4061.3

March 22, 2001

4.4.2 Set-to-touch. An intermediate stage in the drying of coatings, paints, or varnishes which is

reached when gentle pressure of the finger shows a tacky condition of the film, but none of the

material adheres to the finger.

4.4.3 Dust-free. This stage of drying shall be determined by one of the following methods, as

specified.

4.4.3.1 Cotton fiber method. Separate a number of individual fibers from a mass of absorbent

cotton. At regular drying intervals, drop several of the cotton fibers from a height of 1 inch onto the

film. The dust-free time is the earliest time that the cotton fibers shall be removed by blowing

lightly across the surface of the film.

4.4.3.2 Calcium carbonate method. Lie off along its long edge equal portions of the test film and

record the drying time of each portion before dusting. Sprinkle a small amount of finely powdered

calcium carbonate on the film. Repeat the operation on different portions of the film at regular

intervals. After the film has dried tack-free (see 4.5), remove the calcium carbonate dust by blowing

with a gentle stream of air and wiping with a soft cloth or camel's-hair brush. The coating shall be

considered dust free at the time interval that the calcium carbonate can be removed completely.

4.5 Tack-free.

4.5.1 Mechanical method (see 6.1).

4.5.1.1 Tack tester. The tack tester to be used in this method comprises essentially a base or

surface-contacting portion 1-inch square and a counterbalancing portion 1 by 2 inches in area. Both

portions are made up from a continuous metal strip 0.016 to 0.018 inches in thickness. To prepare

the tack tester for use, the base is fitted with several thicknesses of masking tape and paper strips to

provide a means of attaching aluminum foil, and the angle of the counterbalancing strip is so

adjusted that a weight of 5 grams placed in the geometric center of the base is just sufficient to

overcome the unbalanced force.

4.5.1.2 Procedure. At regular drying intervals make preliminary tests of the state of tackiness of

the film by placing a strip of aluminum foil 6 by 1 by 0.0005 inches on the film and exerting firm

finger pressure against the foil. Pressure of the fingertip against the foil shall not be greater than that

required to obtain a contact area of 0.12 to 0.20 inches in diameter. When the foil can be removed

without noticeable pull, proceed with the tack tester. Place the base of the tester on a portion of the

film not previously used and place a 300-gram weight on the base. Remove the weight at the end of

5 seconds. The film shall be considered tack-free when the tack tester tips over immediately upon

removal of the weight.

4.5.1.3 Free from after-tack. Some varnishes retain a tacky condition after the dry-through period

(see 4.7) has been reached. This condition shall not be confused with the tack-free drying stage (see

4.5.4) that occurs previously to the dry-through stage. This state of drying shall be determined by

the following method.

FED. TEST METHOD STD. 141D