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Flash Photography in Show Caves

I recall years back reading an article on how frequent flash photography had been linked to the blackening of straws in a show cave in France. I'm aware that blackening of speleothems was once a result of sooty deposits from early forms of show cave lighting. However, this is more recent. I was having a conversation with a colleague today and offered to send her the information I had on the topic but for the life of me, I can find no trace of such info on my 'puter! I'm starting to worry it may have been one of my far-too-realistic dreams. I could have sworn I read that a paper had been written on the subject, yet Google Scholar is reluctant to assist me.

Has anyone come across this paper?

My (very) limited grasp of physics led me to suppose that perhaps the intensity of light produced from a flash might be enough to excite the molecules in the calcite perhaps resulting in calcium hydroxide, carbon and whatever other species? Please excuse my rudimentary understanding of chemistry (one might call it basic 😂), hence this post.
 

wellyjen

Well-known member
Suggest you search on the subject of the effect of light on biofilms on the surfaces of speleotherms, rather than the effect of light on the speleotherms themselves. Seem to be a lot of papers on it, particularly in show caves and the effect of lighting on the biofilms that form on the surface of calcite. Bacteria, spores and so on, on the thin layer of water on the surface, similar to the sorts of moulds that form on the tiles and porcelain in an uncleaned bathroom and producing discolouration.
Lots of paper on general Google, rather than Google Scholar.
This isn't my field and no time to look at it in depth. A couple of examples:
 

andrewmcleod

Well-known member
I can't imagine the brief flash of light would do anything either to the chemistry of the speleothems or be enough to affect anything living on them. 'Ordinary' light doesn't generally do that much (unlike UV where the individual photons can start to affect chemical bonds more easily).
 
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ChrisB

Well-known member
Interesting question. I don't know the answer but have some thoughts you might Google for more on. If flash was linked to effects on straws, it would have required a fairly long term study of one area where flash was used, and another where it was prohibited, and the two areas to be identical in terms of other pollution such as breathing, muddy shoes, and other forms of lighting. Would a short term test with very frequent flash simulate those conditions?

Could either the duration/intensity of light, or the wavelength, affect things differently? The light from flashbulbs is from oxidation of aluminum, magnesium or zirconium. Electronic flash is xenon, and will have some UV components. Smartphone flash is usually LED, at a much longer duration; there isn't space in the phone for the capacitor necessary to power a xenon flash.

The question for me is whether modern LED lighting, either fixed or on helmet lights, is putting more energy into the surroundings than flash, and at what frequencies? I suspect it is, significantly, but in a quick search haven't found much data on the energy of the flash on 'tourist' cameras or phones, only specialist photographic units.

Paper on the effects of LED lights on biofilms:
 
I can't imagine the brief flash of light would do anything either to the chemistry of the speleothems or be enough to affect anything living on them. 'Ordinary' light doesn't generally do that much (unlike UV where the individual photons can start to affect chemical bonds more easily).
I read somewhere that flash light associated with photography can emit light in the IR spectrum. If flash photography were permitted, going by the number of pictures visitors normally take, it would equate to non-stop flash over a period of several hours each day. We use UV light to demonstrate the refractive properties of straw stals, which doesn't noticeably seem to affect them.

In terms of lampenflora, that does affect the speleothems near the lights. We are in the process of replacing the old bulkhead lights with LEDs, and that has made a noticeable difference. Myself and a colleague are hatching a plan to try to convince management to let us treat the problem areas with hydrogen peroxide when we're closed for maintenance. Our straws are a main feature, and appear nice and clean as they are not directly illuminated (only intermittently with UV light for demonstration purposes).
 

mrodoc

Well-known member
To be honest any flash photos I have taken in show caves aren't particularly great as there are too many man made objects in the way. Nowadays to take photos you can use available light. Here is an example from the Jenolan Caves in New South Wales.
 

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JoshW

Well-known member
. If flash photography were permitted, going by the number of pictures visitors normally take, it would equate to non-stop flash over a period of several hours each day
Think your numbers are well out here, flash duration is generally in the region of 1/1000 of a second if not less, so to get 3 hours a day would need 10.8 million photos to be taken each day. I’d be impressed if any showcave in the world could claim to have that number of photos taken in total let alone of one stal.
 

pwhole

Well-known member
I would imagine that a strobe light would be as effective as a flashgun, and is designed to produce thousands of flashes a day - assuming the light spectrum is reasonably close. I have no idea if flashguns (or strobes) emit any UV as part of their spectrum though - I doubt it. Intuitively, that seems to be the only wavelength that would affect anything chemically or physically, but I'm happy to be contradicted.
 

cap n chris

Well-known member
It would not surprise me at all if there was an old wives tale background to this as a mish mash of repeated hearsay. Showcaves Guides have been told to verbally prohibit flash photography for decades, as a mixture of public safety (so people don't get temporarily blinded and become a danger to themselves), prior to the advent of digital photography it denied people the opportunity to take their own photos thus reinforcing the sales of pictures postcards in the gift shop afterwards, furthermore reducing the noise nuisance to bats in the high frequency range as slave flashguns recharged etc.. soot deposition from earlier visits have very likely been attributed as a quick go-to to further support such blanket bans on the use of flashes. I'd be interested and also somewhat amazed if there was a causal link with flash photography and blackened cave surfaces but there's most definitely a link if you include near permanent lighting as that results in photosynthesis and the vegetation often goes black after it's run out of steam,so to speak.
 
It would not surprise me at all if there was an old wives tale background to this as a mish mash of repeated hearsay. Showcaves Guides have been told to verbally prohibit flash photography for decades, as a mixture of public safety (so people don't get temporarily blinded and become a danger to themselves), prior to the advent of digital photography it denied people the opportunity to take their own photos thus reinforcing the sales of pictures postcards in the gift shop afterwards, furthermore reducing the noise nuisance to bats in the high frequency range as slave flashguns recharged etc.. soot deposition from earlier visits have very likely been attributed as a quick go-to to further support such blanket bans on the use of flashes. I'd be interested and also somewhat amazed if there was a causal link with flash photography and blackened cave surfaces but there's most definitely a link if you include near permanent lighting as that results in photosynthesis and the vegetation often goes black after it's run out of steam,so to speak.
Well this is exactly why I posted. I am a great fan of fact and since I, as instructed, prohibit flash photography in the one part of the show cave where we have a high concentration of well-developed straws, would like to know if it is based on sound reason or simply hearsay. If it were up to me I would prohibit all photography on the basis that it can right royally bugger up the tours and ruin it for others as you constantly have to wait for the happy snappers to catch up. The tours end up running behind schedule, and I get a rollocking for being out late!
 
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