Marked on bulb: F 20 T 12-BL / Black Light / 20 watt
Purchased from www.Granger.com
part # SV 871-8
... Notice that all the strips were fully changed after about 13 to 19 days of 24 hours/day exposure.
... From this we might extrapolate that in direct natural sunlight, betwean 312 and 456 hours of exposure might be needed for the same maximum effect to occur. ...Notice also that the rate of increase in tone (the slope of the curve) is almost a straight line; up until it stops increasing.
...The test strip with three coats of an experimental ground coating increased from A#4 clear up to E6; about 1 1/2 octaves or about 140% increase in frequency.
...I noted an estimate that a factor of 2.75 times longer might be necessary for complete insturments based on their increased surface area (compared to these test strips)
...For instance, the above test suggests that an instrument made without a special ground coating still might have its plate frequencies raised up to 50% with judicious exposure to sunlight.
...It might be equally obvious that if an instrument's plates had not yet reached their maximum frequency due to U.V. light exposure, that being out in direct sunlight or even bright natural indirect sunlight over a long period of time will increase the plate frequency, perhaps upsetting a presently ideal arrangement as the wood changes due to light effects.
...I imagine that we might build our instruments in such a manner that we allow for this increase in plate frequency from sunlight and expose the instrument to enough sunlight so that the plate frequencies become stable and unchanging before we release them to their future new owners.
...Or, as I mentioned above; I hope to learn just how much sunlight will increase the plate frequency and expose new violin plates to enough U.V. light so that they reach their natural (stable) state. Once that is done, the final graduation (adjustment) of the plate frequencies can be carried out and that plate tuning frequency should be permanent.
...Another thought on this line: I could carve and finish the outside of the two plates and rough graduate the inside of the plates, leaving them somewhat too thick (too high in frequency). Then expose the finished (exterior side) only to enough U.V. light to reach this natural stable position. If a tone-raising ground coat is to be applied, it should be applied before this step so that the U.V. can have its 'developing' effect. Notice in the chart above that the plate wood samples with the ground preparations (not bare wood) raised frequency (tone) much more with the effect of U.V. light than did the untreated wood samples, so it is important that this step be done first before final plate graduation.
...A word of caution is in order here, with regard to varnish ground coats. Some of the ones I have experimented with (and used) put the surface of the wood into compression, which distorts wood samples (at least cross-grain) that are violin plate thickness ( 2 1/2mm or 0.100") so free violin plates thinned this much might have a significant amount of distortion. If this becomes a problem, then I would recommend the violin body be assembled before the ground is applied (and then probably also the varnish too) and THEN expose the assembled (completed) violin body to U.V. light (natural sunlight if possible). In order to do this, one needs good information about just how much the wood plates' frequency will increase further.
... I believe that this effect tensions the outside surface of the violin plates and acts to increase sound projection much like tightening a drum head.
... I am working on gathering more information on this subject and will share it in future.
... I suspect that the varnish proper (the six or seven coats of varnish applied on top of the ground coat (or bare wood)) will have little actual affect on the plate tone, even as it cures over time. {However, soft (new) varnish propably does have a significant dampening effect which improves (diminishes) as the varnish cures}
...Please do not be shy to contact me with your insights in this important aspect of instrument making. Perhaps I can act as a clearing house to share good ideas...
