Shellacking: The Modern Revival of an Old Photographic Varnish

I am on the verge of producing my 100th bottle of ÜberSuperBlonde Shellac Varnish for Collodion Plates for wetplaters who have discovered and appreciate its benefits, so I thought it good timing to set down for the record a brief history of the whats, whys, and hows of its development. For many doing wet plate collodion now who have been taught that sandarac is the “traditional” varnish, there might be the perception that using shellac to varnish plates is some kind of newfangled idea or a crazy experiment I cooked up. On the contrary, shellac has been a varnish for plates since the beginning of the collodion process and, in fact, was more widespread in its usage than sandarac. And a few modern wet platers before me seem to have already been using it. This short essay aspires to set the historical record straight, clear up misperceptions about shellac and sandarac, and point out the modern revival of shellac as a finish for collodion plates.

First the whats. Shellac, or lac, is a natural resin derived from the secretions of the female lac bug as it sucks the sap from particular trees. Shellac production is centered primarily in India, where the secreted “stick-lac” is scraped from the tree bark and processed into buttons or flat sheets that are broken up into flakes and sold dry to users. There are various grades and colors of shellac flakes, depending upon the type of trees the lac bug feeds upon and the levels of processing the stick-lac goes through. Selling the shellac dry is important because once dissolved in a solvent (usually ethanol), it has a shelf life of 6 to 12 months depending on storage temperatures. Refrigeration extends shelf life.

Historically, shellac replaced many oil and wax wood finishes in the nineteenth century and itself was largely replaced by nitrocellulose lacquer and later modern acrylics in the mid-20th century. Some woodworkers still use it and extol its virtues. As nineteenth-century photographic literature reveals, shellac was also used extensively as a varnish for collodion plates and especially gained popularity among ferrotypists (tintypists) once positive images on japanned iron (melainotype, ferrotype, tintype) caught on from the mid-1850s. 

There are many historical recipes for shellac varnish for collodion plates, both pure shellac and blended with small amounts of other resins such as sandarac, benzoin, camphor, and Canada balsam (Pinaceae) A recently published chemical analysis of the varnish layer of 221 North American tintypes by art conservation chemist Dr. Corina Rogge of the Houston Museum of Fine Arts confirms this widespread use of shellac, alone or in combination, as a finish on tintypes (“The varnished truth: The recipes and reality of tintype coatings,” Journal of Cultural Heritage, 2013). It appeared in 149 samples, 16 of which were pure shellac. Canada balsam appeared in 173 samples, only one of which was pure — it was used primarily to dilute shellac and sandarac. By volume, shellac was the dominant resin used. The same study also reveals that among the 221 samples, sandarac — the varnish resin most modern wetplaters have been taught to use — never appeared alone. It was always used in combination and most frequently as a minority component with shellac or diluted with Canada balsam, as Rogge displays in this chart:

Rogge’s primary goal in this study was not to demonstrate the preponderance of shellac; rather, it was to determine the degree of correspondence between known published varnish recipes of the period with actual practice among photographers. Interestingly, the level of correspondence that she found — 24% — was poor. Her hypothesis for this result is that the majority of unpublished blends corresponded to the use of shellac-based commercial varnishes whose exact formulae were kept as trade secrets, and personal variations of individual photographers. I support this hypothesis, especially given the popularity of commercial varnishes such as Anthony’s Diamond Varnish, a particularly well-promoted and highly-praised commercial varnish manufactured  for ambrotypes and tintypes in New York City by Edward Anthony’s company.

As a side note, Rogge points out that the nonetheless frequent (44%) appearance of sandarac in some quantity is interesting given the warnings some authors gave against using it, most notably A.K.P. Trask: “Some use gum sandarac for varnish; but it has one fault, which I call a serious one and very injurious to the trade, namely, any dampness coming in contact with the picture will cause it to turn a milky white, sometimes spreading over the whole picture, completely obliterating it. And by carrying a picture in the pocket, where it came near the body, it would change in the same way” (The Practical Ferrotyper, 1872, p. 30). Similarly, a 1870 German Commission for the Testing of Negative Varnishes (for which I credit Peter Kunz for pointing out) also faulted sandarac-based varnishes and recommended instead mastic and shellac for collodion negatives (Photographische Mitteilungen 1870, Band 7, p. 133). 

Such historical questioning of sandarac in addition to frustrations with it that many modern wetplaters have expressed point toward the whys of shellac’s revival. The biggest complaint one hears is that it darkens the varnished plate. Such darkening, of course, can be compensated for by overexposing, but then one hopes that the degree of darkening is consistent, which is no guarantee. It also seems to me rather backwards to have to base one’s exposure on the final step in the process — that’s the tail wagging the dog. Depending on the grade, shellac also similarly darkens the plate, but shellac responds better to decolorization treatments and functions better in a thinner blend than sandarac does, which opens the way to producing a reliable varnish that mitigates against the darkening of the plate. Enter ÜberSuperBlonde Shellac for Collodion Plates.

Minimal darkening is the basic raison d’être of ÜSB shellac varnish, which is carbon-treated and filtered to a lighter hue. But, there’s more to a superior varnish than that. Shellac is known to be a very strong vapor barrier, a desirable trait in a finish for collodion plates. It is also very compatible with microcrystalline waxes like Renaissance Wax, which are very good moisture barriers — another desirable trait. In my opinion, a combo of ÜSB and Renaissance Wax — an idea suggested to me by Dr. Rogge in personal communication — is the best one-two punch against future degradation of a collodion image. As she pointed out to me, the number one reason for degradation of tintypes in her collection is humidity getting to the plate. She has both well-preserved and poorly-preserved plates varnished with shellac, sandarac, dammar, etc. — and the poorly-preserved ones show signs of moisture damage. 

In our pursuit to preserve plates forever we often forget, however, about the aesthetic function of a varnish. In the case of varnishes for paintings, well-known conservator René de la Rie has flat out stated that varnish for paintings is for aesthetics, not preservation (“Low molecular weight varnishes. Interview to E. René de la Rie,” National Gallery of Art, Washington, DC p. 37). While varnishes for collodion plates were generally inherited from paintings (and woodworking), we do have issues of preservation to worry about given the fragility of collodion and the reactiveness of silver. But that shouldn’t entirely trump aesthetics. This is where having various options with which to finish an image comes into play. Sandarac offers a high gloss and depth to a plate, but at the cost of a change of hue and darkening a stop or two of exposure. While it might the best choice for some plates, it isn’t for others. Decolorized shellac, properly applied and dried, offers a similarly high gloss (I think on average it’s slightly less than sandarac) and a lightly warm hue without much darkening at all. Being a thinner varnish, depth is not as dramatic as with sandarac — it produces a more direct and cleaner look to the image, but not without some depth. And it effectively increases the speed of your lenses, always a concern for wetplaters. These are some of the aesthetic and technical considerations to note in the choice of any finish. 

The thinness of ÜberSuperBlonde has also been noted by users as having the benefit of easy workability on the surface of the plate without the extra step of heating the plate and/or varnish to get it to flow well. This workability is particularly beneficial in varnishing ultra large plates. Care does need to be taken to avoid spots that are too thin opposite the pour-off edge, but proper technique alleviates that. At the same time, any backwash lines that might appear on the pour-off edge are shallower and not as noticeable compared to what can happen with a thicker sandarac. Finally, shellac dries to the touch more quickly when heated after pouring off and cures to a safe hardness within hours (although I would give it a couple days to fully cure). This trait has the advantage of less chance of dust and such getting stuck in the surface and allows for quicker turnaround of finished plates to customers, something that no doubt attracted the 19th-century tintypist whose livelihood was directly related to the number of plates he could successfully turn out per hour. Giles Clement’s recent three-dozen plate performance at a cafe in Nashville where he beautifully shellacked and delivered all of them within 24 hours to customers is the modern example of this practicality.

So, if shellac has been around for so long, was used far more widely than modern teachings would suggest, and displays such good archival and aesthetic results as well as other side benefits, why is it that more modern wetplaters don’t know about it? Or, differently asked, why and how did sandarac become modern gospel? My pet theory is that the modern collodion revivalists made selective use of historical sources and, in effect, made personal decisions about what varnishes to adopt and then teach in workshops. For those folks working primarily with negatives, the adoption of sandarac varnishes makes sense because the vast majority of historical recipes containing sandarac are specified for negatives (the German Commission for Testing Negative Varnishes notwithstanding. It should be noted, however, that there are shellac-based recipes for negatives as well—it is not limited to positives.) It would be easy then simply to use the same varnish for positives. Once taught as THE (not just one) traditional varnish to a generation of students, published in guides and eventually posted to websites, one can see how sandarac would be spread exponentially and become gospel. I also suspect — with nothing but circumstantial evidence — that when mention of shellac has since come up it faces an unfortunate prejudice. Shellac simply isn’t as sexy and exotic as sandarac. It sounds (and is) cheap and prosaic. It’s the stuff of everyday carpenters, not practitioners of an arcane photographic process. Which is why I sex it up with the fancy bottles I sell ÜSB in…..

How then did I come around to shellac and devise a way to enhance it in the form of ÜSB? That development was driven by one part tech-geekiness, one part historical awareness, one part critical consciousness. After diving into nineteenth-century photography journals and books for geeky fun, I came across a wide range of varnish recipes and started wondering. At the same time I started questioning the (modern) orthodoxy, a habit well-learned through years of college and graduate training in history and literature. Amid broader researches and experiments on natural and synthetic resins I was conducting in late summer and fall 2013 (see The Varnish Report), a pivotal moment came when I came across Corina Rogge’s article (cited above) while it was still in press before publication. That someone actually took the time to conduct a scientific analysis of tintype varnishes to determine a correlation between historical literature (i.e. theory)  and historical practice — rather than simply assume that actual historical practices followed from what was published as recipes — deeply impressed and inspired me. Thus I owe a great deal to Corina and the several emails we exchanged discussing the properties of various resins and their appropriateness for collodion. 

The idea to decolorize shellac, however, came through researching alternatives to the usual bleaching through chemical processes involving sodium hypochlorite (not good for collodion). I stumbled upon an undergraduate research project involving the archival properties of shellac done by a student who went on to the Conservation Course at the Victoria and Albert Museum in London. In it, Stephen Copestake reported that “[T]he experiments to decolourise shellac were quite profitable, although the process is time consuming and messy. The palest commercial grade of flake shellac is called Platina, a dewaxed decolourised grade, and is a lot more coloured than bleached shellac. After stirring a solution with activated charcoal for some time, and filtering under vacuum, the resultant solution is slightly paler than that of bleached shellac, being a pale yellow colour. The films obtained from these solutions are virtually colourless. These experiments showed that shellac varnishes could be made as pale as bleached shellac, by using commercial grades of flake shellac and activated charcoal, with a minimum of equipment.” (“The ageing & stabilisation of shellac varnish resin,” Conservation Journal, April 1994 Issue 11). The principle is simple and ingredients and gear easy to obtain. And in addition to decolorizing the shellac, activated carbon filtering also removes virtually all impurities, leaving a very clean, clear, and smooth liquid. At this point Collodion Bastard and professional chemist Michael Koerner provided more detailed guidance on how to set up a vacuum filter capable of removing powdered activated carbon that has been mixed and soaking in dissolved shellac. I added centrifuging before vacuum filtering on my own because in theory it made sense as a way to aid the removal of carbon (I remembered some things from high school chemistry). 

After testing several prototype versions of shellac processed in this fashion, I announced very pleasing results on the Collodion Bastards Facebook group. I never intended to market this stuff, but one member, Brian Joseph of Los Angeles, insisted on purchasing a bottle and he reported back being very pleased with it. Others wanted to try it and the next thing I knew I was upgrading equipment and shopping for ingredients in bulk quantities. The first couple dozen bottles suffered from light precipitate that eventually settled out, but further improvements to the filtering process have largely eliminated that problem. I do want to recognize and thank those early adopters (you know who you are) for having faith and being willing to try something new—that’s true pioneering and Collodion Bastardly spirit….

Although helpful, centrifuging the carbon-laced shellac is not necessary, as Ana Tornel has demonstrated with the version of decolorized shellac that she has started to produce for the European market following my instructions and adding her own touches. We both brought samples of our shellac varnish and examples of shellacked plates to the 2014 European Collodion Weekend where they were met with universal acclaim.

While good technique in applying any varnish is key, many new users have noted not only very nice results with ÜSB shellac, but also a decrease in anxiety at the prospect of having to varnish plates. I personally very much disliked varnishing and was not very good at it; I now look forward to it and enjoy thinking about how I might want to finish a particular plate: burnished or unburnished with shellac or sandarac; wax or no wax on the shellac or maybe just wax and no shellac; or maybe two coats of shellac…. The bottom line here is that you should be able to expose your plate as you want and then have options that will match the particulars of your plate and your own personal aesthetic vision. 

After testing a wide range of natural and synthetic resins, I kept coming back to the plates shellacked with ÜSB as the ones I liked best for their look, their feel, and their ease in varnishing. Shellac in various concentrations and minor variations is all I use now and I’m very happy with it. Others will quite likely have different tastes and different criteria for what they judge as “good” or “bad,” but it is my hope that shellac will earn a little respect and be recognized as a varnish for collodion plates that is as good if not better than any other—just as it had been in the early days of wet plate photography. 

(For more details on the production of  ÜberSuperBlonde Shellac Varnish for Collodion Plates click here; for ordering info, click here.)