Results

The dielectric constant as determined by the method below is: 2.7. 2.7 is the capacitance of the varnished cotton (0.065 nF) divided by the capacitance of an air capacitor (0.024 nF).

The test was made using a parallel plate capacitor where the plates were aluminum of dimensions .8mm x 101.6mm x 101.6mm. The spacing between the plates was 4mm. To calculate the dielectric constant two capacitors were made: one with varnished cotton for the dielectric, the other with air for the dielectric. The dimensions of the varnished cotton was 122mm x 122mm (thickness unknown). The air gap for the air capacitor was 4mm. To get 4mm thickness of varnished cotton, sheets were added until 4mm was reached. 9 sheets were required. The capacitance of each was measured using the capacitance measuring feature of a Fluke 187 True RMS Multimeter. Rather than making yet another air capacitor measurement, the results from here were used. The measurements for the varnished cotton capacitor are detailed in the pictures below.

Varnished cotton capacitor

A sample measurement being made (0.065 nF). The meter is in relative mode.

The test setup.

Construction

The varnish that was used.

An unvarnished cotton sheet is on the left and a varnished one is on the right. Only one coat of varnish was used.