Hi Martin,
Thank you for the additional details, which do make a difference in how I think about the question. My short answer is that given the frequency and ongoing nature of the sleepovers, I'd be more likely to advocate for some alternative to the black light than if it had been proposed for a one-off or infrequent event. My understanding is that black lights emit UVA radiation, which is less harmful to collections than other types of UV (like sunlight), but still, something that we typically make a concerted effort to filter out. It's not a crisis in small amounts; in fact, conservators sometimes use it for object examination as in this video. But light damage is cumulative and irreversible, so I would have reservations about the amount of exposure you're considering.
Though neither specifically address black light, the Conservation Center for Art and Historic Artifacts' resource Light Exposure for Artifacts on Exhibition and the Northeast Document Conservation Center's Protection from Light Damage offer good explanations for how to think about exposure over time, and thresholds for exposure to UV light. Depending on what equipment you have, you may want to take readings with potential lighting configurations in place and try to calculate how much time you could safely recommend for the collections to be exposed (and what that would translate to in terms of hours per event, events per year, etc).
But since these events are ongoing, I would be more inclined to suggest alternatives early on. Before receiving your additional info Richard Kerschner, a conservator with expertise in lighting, suggested the following, thinking you meant a one-time event:
Practical advice would include using as little black light as possible for the shortest time possible (perhaps several bulbs illuminated during the few hours of major activity and then turned off for the rest of the night such as during when participants are asleep, with a dim regular light to move safely during the night as necessary. Very few specifics are provided for the event, but since this is a library and not a museum, books are closed and packed on shelves, minimal museum quality objects hanging on the walls (?) there would be very little possible damage with one nights exposure. However, it the event becomes very popular, it could be a foot in the door for additional events and exposure.
You might also consider moving items with the most artifactual value to different storage, or boxing or otherwise covering them; without knowing event details there might be other reasons, like presence of food/drink and security concerns, in favor of this too.
Finally, I would look into potential health risks for attendees. It may depend on specific bulbs, their placement, and again duration of exposure, but it's been standard practice in places I've worked to wear UV-filtering protective goggles even during short examinations using small UV lights. It may also be possible to angle or shield bulbs so that people can't stare directly into them.
I hope this helps you think through the situation,
Rebecca
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Rebecca Smyrl
Connecting to Collections Care Monitor
Library & Archives Conservator
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Original Message:
Sent: 09-26-2025 13:52
From: Martin Christiansen
Subject: Black lights in a library
Thanks for looking into this!
The library in question is our collection of historic and contemporary books; it is the historic ones that concern me. They are generally either cloth or leather-bound, stored in open shelves. This room has no windows, and the overhead fluorescent lights are on only when the room is occupied, possibly 4 hours a day. Otherwise, the room is dark.
The proposed event, or series of events, is our museum sleepover. How many times it happens depends on how many Scout troops, et cetera, want to have a sleepover. The usual timing is 1 or 2 nights per week, throughout the school year. It is proposed that the black lights will be on for about four hours on each of these nights.
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Martin Christiansen
Collections Management Specialist
EcoTarium
Worcester, MA
Original Message:
Sent: 09-26-2025 09:12
From: Rebecca Smyrl
Subject: Black lights in a library
Hi Martin, I don't know much about this topic, but I'm looking into it and I hope to get back to you soon. In the meantime, more information about your library could be useful. From your website, it looks like you have extensive natural history collections including books of plant specimens, but do you also have a separate library of books? If so, knowing a little more about the time periods and binding materials represented, how they are stored (open shelving, in boxes) could be helpful in thinking about the lighting risks and benefits. Also whether the space includes exhibition cases and/or collections hanging on the walls. What kind of light exposure do the objects usually receive (i.e. are there windows with or without UV film and/or other coverings, are overhead lights on all day, is the space used only occasionally and dark when not in use)?
I'm curious about the event as well, if the proposal is for the black lights to be on continuously for 8-12 hours with attendees occupying the space for that entire time, and if there might be some room for compromise. In addition to the collections, there may be human health and safety factors that I'd like to look into a little more.
Thank you for any additional info you can provide!
Rebecca
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Rebecca Smyrl
Connecting to Collections Care Monitor
Library & Archives Conservator
Original Message:
Sent: 09-25-2025 13:58
From: Martin Christiansen
Subject: Black lights in a library
Does anyone have information on the risk of light exposure damage from black lights? I've been asked to weigh in on a plan to put black lights in our library for an overnight event, but I don't have enough data to form an opinion. Thank you!
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Martin Christiansen
Collections Management Specialist
EcoTarium
Worcester, MA
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