{Page Two}
...Fuller's Earth Varnish Ground Experiment 2016...
...This research experiment began innocently enough one afternoon when my wife and I were reading and she asked me what is 'Fuller's Earth'? I said I did not know but said I would look it up in my Materials Handbook {Brady and Clauser, eleventh addition} from my Engineering classes at Oregon State University back around 1969.
...The chemical formula they listed reminded my of the chemical composition of varnish ground of famous golder period violins published in The VSA journal articles on the subject. I checked and they were very similar. The feature of famous violins of this period is that they had the characteristic of dampening the overtones above 2,300 HZ (If I remember correctly).
...It made sense to me that the instrument makers of northern Italy probably used a local product for the ground formula. To test the validity of this hypothesis, I ordered a supply of Fuller's Earth (mined in America) and made up wood samples to allow me to test many different configurations of ground and varnish materials in different combination, and applied in different orders; both for spruce and maple violin making wood.
...Some of the (17) violin wood samples prepared and tested for acoustical properties im March, 2016.
...These samples are the thickness of violin plate wood approximately, and all make from the same first quality sitka spruce; quarter sawn, and carefully the same size and thickness.
...This photo shows the test setup for gathering data for analysis on acoustical properties due to varying ground forumlas applied.
...The spruce dowel drops vertically from a stop at the top and the samples are supported the same for each sample.
...the recorder is a zoom digital recorder recording with the wave sound format (most accurate).
...Sample results were analyzed both by ear and then separately by a computer based sound analyzer program. {Wavepad Sound Editor V5.48 (c) NCH Software} Select the peak of a tap response; and under 'Tools' drop down menu, select "Frequency Analysis" (FFT) to see sound spectrum for comparison purposes.