The investigation was initiated to develop additional tests to supplement Quartermaster Corps Specification No. 3-16A, which is identical with Federal Board Specification No. 18, so that a revised specification could be written which would incorporate the necessary requirements for a satisfactory spar varnish for use on aircraft. The tests included in this specification are: Appearance; color; flash point; nonvolatile matter; draft test; film test; water test; elasticity. The additional tests were a gas test and durability or outside exposure test, which have always been a part of Air Service Specification No. 14001-C, a viscosity test, and a baking test. The last test was made in order to determine whether the varnish could be used in a dual capacity as a baking varnish and a spar varnish. ... The substance of this investigation was to make a study of the relation between laboratory tests and exposure tests with the desire to eliminate the latter and eventually modify Air Service Specification No. 14001-C by the addition of new tests if necessary. Many specifications for spar varnish do not include outside exposure as a necessary or qualifying test. The study was also made on the advisability of including a baking test on the spar varnish specification so that one material could be used either as an air-drying or baking varnish.