Pixiq

Recently, I made a short trip to Sardinia – a mere hop and a skip by air from Rome, even on Ryanair, with no particular goals other than to be a kind of parasite because my good lady had some work down there doing hotel inspections before managing an archaeological tour.

One of the (many) reasons I love being in Italy is that you never quite know on waking up where a day will go. Completely unplanned, we ended up in caves, fabulous caves with incredible concretions, stalactites and stalagmites where the appeal to a sense of awe was vast and ample compensation for walking down and back (over 600 steps each way) to Neptune’s Cave (Grotto di Nettuno) near Alghero in Sardinia's north west.

Typically, there were notices around barring all forms of flash photography. I asked about this and was first told it ‘damaged’ the caves... when we talked more, the guide admitted it had more to do with the way people stop and inconvenience others. In fact, this being Italy where people are still prepared to think for themselves, the guide (a geologist) said I could hang back in the group and get some shots…it would never happen in the UK where an authoritarian jobsworth streak is the raison d’être for many. Yes, Italy might be a mess economically but I love it. There is always a way!

Over a good lunch (another prime ingredient in Italian travel photography) I did some back of the envelope calculations (again) because I have never believed for one minute the so-called claims advanced for flas-induced damage. It is that physicist's nose for BS, again. In fact, flash guns potentially cause less damage than the continuous lighting used to illuminate caves, works of art and the like as s simple calculation can show.

A flash is only very bright (intense) because the energy is discharged in a very short time. My most powerful portable flash is a Nikon SB900 that has an energy output per flash that seems to be at most 100 Joule (Ws) though working from capacitor values and assuming it is charged to around 350 volt this is optimistic (it would be closer to 70 Joule) but 100 is an easy number.

The flash looks much brighter than the continuous lamp for, at full power, it discharges in 1/880^th sec….which is equivalent to a momentary power output of  88,000 Watt….pretty high intensity  but what matters is the total energy emitted, not how quickly, because it's those little bundles of energy (photons) reaching the surface of a painting or something else sensitive that potentially does the damage, especially. That likelihood is greater if they happen to have wavelengths in the UV range and, being more energetic, can help break down pigment molecules causing fading, for example. Most camera-top flashes are much less powerful that the one I used and you'd need many thousands per hour to compare with even modest continuous lighting.

There is an excellent article written by Dr Martin H Evans entitled Amateur Photographers in Art galleries - Assessing the harm done by flash Photography. It's recommended reading because it is very clearly and rationally written. In it, Dr Evans considers the history of objections and produces a careful analysis. He understands the problems completely: many of those prejudiced against flash simply repeat a mantra knowing nothing about the science involved. He cites one incredible example based on a misunderstanding of the idea that flash ‘freezes’ movement  “A friend of mine was once admonished by a museum attendant, who said that the light was so bright that it could freeze an object, and this sudden cold shock would be damaging to a delicate wooden exhibit!”

Some cynical folk will venture the idea that, if we cannot take our own pictures then we will be that much keener to buy guide books and cards…given upkeep costs that is not unreasonable as long as the shots are good and the printing does not look as if someone got the Photoshop Kiddies finger-painting kit for Christmas.

However, whereas the case to made for damage might be 'specious', I would support a general ban on flash guns for all places with works of art on aesthetic grounds alone. Organisers in museums and galleries have usually done a superb job in lighting to create the right ambience and make sure damage via continuous light is minimal. A succession of random flashes from people seemingly unable just to look and experience what many of us get from art… is infuriating. But any antagonism I experience there pales into insignificance with the venom I feel towards those ingrates who allow their mobiles (with their moronic jingles) to interrupt classical concerts. This is very common in Italy.

When it comes to protecting ancient sites, works of art and so on what makes a real difference other than the obvious wear and tear from tramping feet and sticky hands?

In the past, fumes from coal-burning were extremely damaging to works of art in big cities and acidic effects of sulphur dioxide ate away at buildings made of limestone whilst tars and soot coated others. Hydrogen sulphide, another gaseous pollutant from coal burning, darkens pigments containing lead (or mercury) employed  in paintings - those old masters did not start off dark and sombre!  

Major clean-ups in cities can give a false impression. Visit Oxford for example and the light-honey-coloured limestone, of which most colleges are built, looks as if it has always been there. Well, it has in a sense, at least for hundreds of years but In 1968, when I first went there as an undergraduate, many buildings were still blackened with a thick crust of nasties. All details on carvings, for example, were eaten into. In Athens much of the marble façade on the Acropolis was eaten away by the acidic effects of sulphur dioxide which dissolved in rainwater produces sulphurous acid.

Another good read for those interested in the why’s and how’s is David Saunders, authoritative National Gallery technical Bulletin (on pollution effects). 

It has not all ended with cleaner air for  serious problem arises from admitting humans (in much larger numbers these days) to places where cave paintings, sensitive crystals and so on have remained secure from light, in conditions of constant humidity, perhaps for thousands of years. Interior conditions change when humans are allowed to flock in.

• Our first crime is that we breath – easily rectified but the solution is drastic  Our exhalations contain CO₂ and a great deal of water vapour so, where sensitive restoration has been carried out some museums allow only a few people might be admitted at a time into an environmentally controlled space.
• We perspire… yet more moisture and, how can I put this,  there is also the delicate question of other 'gaseous emissions' from humans that include methane (CH₄) and hydrogen sulphide (H₂S)

Methane is certainly a problem in the atmosphere where it contributes massively to global warming – cows, for example, produce enormous amounts. Hydrogen sulphide is definitely bad news – in low concentrations it smells of rotten eggs (its common name is rotten-egg gas): when you can’t smell it (at high concentrations) then it is deadly. In many churches in Italy you can find paintings darkened by age, the original pigments affected by atmospheric contaminants. So, should the advice to congregations be to keep off beans in the diet at least before Sundays? Probably not, the tallow candles and coal and wood fires probably did far more damage with what was contained in their smoke…than any  ‘pooping peasantry’

Pigments used by Renaissance artists included salts of arsenic, antimony, lead and mercury. Whereas, for example, Lead carbonate is white and much used both on its own as a white in paints (and also to lighten other pigments and produce pastel tones) any contact with hydrogen sulphide promotes the formation of Lead Sulphide which is black…

I would love the chance to see again some of the cave paintings at Lascaux in France now closed to visitors or to witness the wonderful crystal formations in Mexican caves. The danger is in believing its OK for me but not others…but we are all a bit like that when it comes to it.