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Canid skull from the US Exploring Expedition (1838-42), treated with mercuric chloride.

Canid skull from the US Exploring Expedition (1838-42). The skull had been treated with mercuric chloride as a preservative during the expedition. Later exposure to ultraviolet radiation from window light or fluorescent lamps caused the mercuric chloride to convert to mercury sulfides and metallic mercury. Photograph by the Conservation Section.

Photograph of staff members sitting at laser stations
Photography by Marlene Yandrisevits.

Lasers are a staple in science fiction—in real life, they are known by scientists to be some of the most powerful tools to work with. The field of conservation has been exploring laser technology as a promising and flexible cleaning tool for difficult objects and media. Recently, the Conservation Section here at the National Museum of Natural History was able to take part in a Smithsonian Institution-wide exploration and training with lasers. Mariana DiGiacomo describes her fun and fruitful laser adventures in cleaning all different types of media.

To us, what you worked on was simply "the laser project"—what was the project, and who was part of it?

Mariana DiGiacomo (MD): The laser project began in 2014-2015 when Bartosz Dajnowski and Martin Cooper began giving workshops on using laser to clean objects in collections. Between February and May of 2017, the latest stage of this laser project took place. Ingrid Rochon and I (Mariana DiGiacomo) of the National Museum of Natural History, Carol Grissom and Rebecca Kaczkowski of the Museum Conservation Institute, Marlene Yandrisevits from the National Air and Space Museum, and Ariel O'Connor and Helen Ingalls from the Smithsonian American Art Museum composed the exciting multi-unit 2017 lasers project.

Laser tests on shell with a variety of different ink types.<br> Photography by Ingrid Rochon.
Laser tests on shell with a variety of different ink types.
Photography by Ingrid Rochon.

Why did the laser project start? What were you trying to explore?

MD: This was the most recent of a series of laser projects hosted by NMNH. We were motivated to begin exploring and training with lasers because laser technology has been widely used in Conservation, especially abroad. This technology had been previously little explored at the Smithsonian. The 2017 stage of this project was designed to train people under the Laser Institute of American in preparation of advancing laser technologies; in the future, we'll have trained individuals who can easily learn and handle lasers that can be used to clean a variety of different materials and objects.

What kind of machinery was involved with the laser project?

MD: We used high frequency 1064 nanometer lasers. The particular model is called a GC1 laser.

What were some main results of the project?

Before and after laser cleaning of plaster mix on fossil slab.
Before and after laser cleaning of plaster mix on fossil slab.Photo by Mariana DiGiacomo.
  1. Training of staff: This was the most important result. We now have staff from different units who are trained, especially in the safety of lasers. With this comprehensive training, future projects that involve lasers only need to focus on procuring or renting lasers, with the trained staff already at hand.
  2. Testing on various Natural History media: Ingrid tested on shell and feather. The laser did a good job at removing certain types of ink from shell, but it was too strong/aggressive for feathers (even at the lowest settings). Ingrid tested different levels of cleaning on wood. I (Mariana) tried lasers on two different types of fossils: 1) a black matrix on top of bright red bone, and she could not remove the black; 2) mastodon (teeny pieces of tooth coated with shellac), which lasers also couldn’t clean.
  3. Successful cleaning of fossil slab: There was a successful treatment of a slab with an Ichthyosaurus fossil embedded in it. The fossil itself was not touched. Previously, the slab had been covered with plaster, paint, and sand to mimic the ocean floor in past exhibits. The preparatory, Adam Behlke, had been previously sanding down all of the coating, which was extremely time-intensive. With the laser, I was able to clean the entire slab in just five hours.
  4. Testing cleaning on outside of buildings: Carol Grissom tested on stones on the outside of the Smithsonian Castle. She was able to separate a dark stain. We also tested outside of NMNH, which beautifully cleaned the stonework exterior.
  5. Testing on sculptures: Ariel tested on many different metals, specifically in the sculpture context. At the Smithsonian American Art Museum (SAAM), they also conducted tests on marble sculptures.
  6. Exploring laser cleaning on textiles: Marlene tried cleaning a textile but, as expected, it didn’t work.
  7. Contributing to a PhD dissertation: I was able to use some of the laser testing for my doctoral dissertation.

Ultimately, an important outcome of our laser project was realizing that lasers can be extremely delicate but also extremely destructive at the same time if not used correctly.

What are the implications of your results?

Laser testing on feather
Laser testing on feather. Photo by Ingrid Rochon.

MD: The most important implication is that training with lasers is important. You are giving people the tools to be able to use powerful lasers in the future. The Smithsonian now has internal capacity to use lasers rather than depend on outside contractors.

Natural History has fewer conservation practitioners that other museums— it's easy to overlook conservation in Natural History. The fact that we at Natural History were able to host this exploration in lasers showed how much growth and leadership is hosted within conservation in natural history (e.g. testing laser cleaning on fossils).

When you're doing conservation, you're taught many different techniques. Lasers are just a different treatment technique—solvents can also be dangerous. If done properly, like any other technique, lasers can be a great conservation tool. It can be fast and non-damaging. All you have to do is learn this technique. It's not a new technique, it just requires something that is expensive and that not many people get to try and use. If you're informed, now you can include lasers as one of your viable options for treating difficult and diverse media (e.g. huge building, huge sculpture).

Before and after laser cleaning on metal. The cleaning was delicate enough to remove rust but keep paint
Before and after laser cleaning on metal. The cleaning was delicate enough to remove rust but keep paint (R).
Photo by Marlene Yandrisevits.

What were the greatest challenges of the laser project?

MD: Of course, scheduling was the greatest challenge! Getting different people from different museums in the same room at the same time during only so many hours a day was difficult.

Another challenge we knew that we would have to grapple with was establishing trust with collections managers. After all, we hoped to use loans from various departments for our media tests. We realized that it was difficult to pursue testing with loaned objects that might pose a safety hazard (e.g. cadmium).

What are the pros and cons of using lasers in conservation?

MD: Big pros:

  • If done right, lasers are extremely safe. If you make sure use appropriate local exhaust ventilation and wear goggles, lasers are arguably safer than other techniques.
  • Lasers are fast and accurate.
  • Lasers offer different levels of cleaning, while other techniques solely offer clean or dirty as the cleaning binary.

Big cons:

  • Lasers require certifications and training.
  • Lasers require expenses in renting and/or buying the lasers as well as their associated costs (e.g. exhaust, goggles, screens).


Do you have any especially fun anecdotes from the laser project?

MD: When something is very dirty, it's extremely satisfying to clean it with a laser. It's almost inconceivable how clean something can become with a laser. Removing rust from metal is especially satisfying.

Laser cleaning can both completely clean this metal surface (L) or provide various levels of cleaning (R).
Laser cleaning can both completely clean this metal surface (L) or provide various levels of cleaning (R).
Photography by Ingrid Rochon.

It was cool seeing the faces of people who visited for demos. Their faces of amazement at how clean objects could become with laser cleaning were nice.

A memorable experience was cleaning rust from an object in water. When you shoot a laser at the object submerged in water, the rust stays in the water. All of the rust particles fly into the water, and eventually the beam hits the teeny tiny particles so that the reaction creates a glittery snowglobe effect. It's a beam of white light and all these glimmering particles in the water—super science fiction-like. It was a lot of fun!

Skull of a single-tusked male narwhal (Monodon monoceros); photography credit: Alyx LeBlanc
The sparkly effect created by aiming lasers at iron object submerged in water.
Photography by Ariel O'Connor.

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