Ultra Violet light reflects off the surface coatings of an instrument, which is normally very helpful for being able to see evidence of retouch and other interventions of interest when producing a condition report. However, a think coat of shellac that is invisible to the naked eye and used as a protective measure will mask underlying coats of varnish and retouch, rendering UV useless. Anecdotally I first became aware of this when working with Jan Röhrmann and Brigitte Brandmair on the Stradivari Varnish book at the Ashmolean. Upon carrying the Messiah into the room that was floodlit with UV, it reflected an orange colour rather than the off-white typical of Cremonese varnish. For a moment of panic it seemed completely inconsistent with Cremonese varnish, but very quickly we were able to establish that in areas where the protective polish (invisible to the naked eye in normal light conditions) had been missed there was all the evidence we needed to be sure that the layers below were consistent with Cremonese work. The heart-in-the-mouth experience can be evidenced in the Stradivari Varnish book.
In this case, I was looking at a Stradivari violin that had also passed through Vuillaume and had anecdotally passed through the hands of Luigi Tarisio (at least, Vuillaume sold it in 1855, the year after acquiring the violins from Tarisio’s estate). As can be seen from the photograph above, much of the back of the instrument was unpolished and showed very typical Cremonese varnish, but the front was almost completely opaque with over-polish, so that although the UV photograph invites further investigation, it has relatively little use for establishing the condition of the instrument.
A good deal of condition issues that the belly suffered from are visible to the experienced naked eye. In particular, a significant area of retouch had been done with a varnish that included dragon’s blood resin as the red pigment component. Since this fades over time, the areas in question had a greenish-brown hue to them that is obvious once spotted. However the purpose of a condition report is to alert the client, who has no forensic expertise and very little technical knowledge of violin restoration, to the ravages of time that have befallen the instrument, in order to be able to assure them of the quality of the restoration work, and provide transparency and assurance.
Here are the steps I took to render this image so that the restorations were more visible. Top tip – if you are using a computer on battery, make sure that the backlight is set to maximum before you start. I will say it a few more times, this is a process of art and judgement. There are probably other ways to get the same result or better, and it would be a miracle if I was able to reproduce the same result twice. Doing this repeatedly, I find that working through the following order (even if you elect to do nothing with any of the tools) seems a good process:
Colour Balance
Hue and Saturation
Contrast
Colour Balance (again)
Exposure
The first stage is to use the Colour Balance to try and pick out the retouches and make certain that they are as visible as possible using this tool.
Using the Hue and Saturation tool, I played around a little bit with the levels, increasing the saturation significantly.
Pushing up the Contrast to 100% and playing with the brightness at this point produces a more marked difference between the two varnishes.
Then another go with the colour balance.
I’ve added the original photograph in for this final play around with the Exposure, overall I’ve worked this up so that the bare wood is a good yellow colour, and the retouch has a blackish hue to it by contrast to the reddish colour transmittedf by the original varnish.
There is a fine art to this kind of colour separation, and no specific process or settings that can be applied to all instruments, especially as if you are trying to isolate areas of retouch, they will be different depending on the composition and weaknesses of the retouching. It may also be necessary to work on the same photograph in different ways in order to put emphasis on different layers of restoration. The contrasting images of the same violin have different strengths and weaknesses.
As always, the purpose of these images is to highlight areas of interest. A detailed report can isolate each area and provide the analysis and narrative that is required for each restoration. This is all part of creating a more transparent way of presenting old instruments, in order to give the potential buyer the security of understanding the quality of restorations.
