Standard Active Last Updated: Nov 14, 2017
ASTM D115-17

Standard Test Methods for Testing Solvent Containing Varnishes Used for Electrical Insulation

Significance and Use

4.1 Control—The following tests are useful for control purposes during the manufacture and use of varnishes, and for determining the uniformity of batches:

4.1.1 Specific gravity,

4.1.2 Viscosity,

4.1.3 Flash point, and

4.1.4 Nonvolatile matter by weight.

4.2 Performance—The following tests are useful for determining the performance of varnishes during application and use:

4.2.1 Drainage,

4.2.2 Time of drying,

4.2.3 Build,

4.2.4 Dielectric strength,

4.2.5 Thermal endurance,

4.2.6 Varnish compatibility,

4.2.7 Salt water proofness, and

4.2.8 Oil resistance.


1.1 These test methods cover tests for solvent containing varnishes primarily intended to provide electrical, mechanical, and chemical protection for electrical equipment. These test methods include tests for control and performance as follows:




38 – 42

Dielectric Strength

43 – 48


26 – 32

Flash Point

18 – 20

Nonvolatile Matter

21 – 25

Oil Resistance

54 – 56

Preparation of Test Specimens


Specific Gravity

9 – 12

Temperature Index


Time of Drying

33 – 37

Varnish Compatibility

51 – 53


13 – 17

1.2 Where the entire test method is included in this standard, the precision and bias are not known unless given in the stated method.

1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 5.

Note 1: There is no equivalent IEC standard.

1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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Book of Standards Volume: 10.01
Developed by Subcommittee: D09.01
Pages: 9
DOI: 10.1520/D0115-17
ICS Code: 29.035.60