With the recommencement of laser cleaning activities at the V&A, I’ve had the exciting opportunity to work closely with our conservation teams on a variety of projects. The aim of our collaborative work is to preserve some of the museum’s most delicate and historically significant objects and introduce the laser cleaning technique to new members of the department.
My first task was looking into laser cleaning of plastic buttons affected by various surface contaminants, such as blooms of plasticizer, sticky residues, or dirt. The blooms, which are surface deposits resulting from the migration of plasticizer, can obscure the original appearance of the buttons, and so can the sticky residues and dirt accumulating over time. We can gently remove these deposits, bringing back the vivid colours without damaging the underlying buttons.
So, how does this work?
Laser cleaning is a precise, non-invasive method that uses focused light to remove surface contaminants from artifacts without damaging the underlying material. Whether they are made of metal, stone, or plastic, all materials absorb light in different ways. When a laser is directed at an object, it emits a highly controlled beam of light at a specific wavelength (or colour). This light is absorbed by the unwanted dirt, grime, or pollution on the surface of the object. As the contaminants absorb the light, they break down, essentially vaporizing off the surface. What’s left behind is the clean, original material underneath.
The Er:YAG laser in particular emits light at a wavelength of 2.94 micrometers, which is highly absorbed by water, a key component in organic surface coatings or contaminants like biological growth or paint layers. When the Er:YAG laser beam hits the surface of an object, it’s absorbed by the thin layer of dirt or unwanted material that contains moisture. The energy from the laser is then converted into heat, which causes the unwanted material to evaporate in tiny bursts. This process happens in a controlled and precise way, layer by layer, allowing conservators to remove dirt or surface coatings while leaving the original material intact.
As part of my work, I am also analyzing laser-cleaned materials using a range of advanced techniques available in the Science laboratory, including optical and digital microscopy, Scanning Electron Microscopy (SEM), and Fourier-Transform Infrared Spectroscopy (FTIR). These tools provide valuable insights into the materials’ composition and their specific reactions to laser cleaning. By examining the surfaces at a microscopic level, I can assess the precision and effectiveness of the cleaning process, ensuring that the objects are treated without compromising their integrity or causing any visible or invisible damage. This approach helps to fine-tune our methods for optimal preservation.
The dirt was partially lifted off by the laser, and the surface could be gently swabbed with cotton to clear it. Note that the cracks look less conspicuous after treatment, due to the removal of the dirt.
The combination of science and conservation practices ensures that we can preserve these items for future generations. While conservators possess an intimate understanding of the materials and techniques, scientists bring expertise in the physical and chemical properties of the materials. By working together, we can tailor the use of cutting-edge technologies, like lasers, to address specific conservation challenges.
The fellowship is made possible thanks to generous funding and donation of the Er:YAG laser by Ed and Anne Teppo.
We are grateful to the UKRI Arts and Humanities Research Council (reference AH/V012134/1) for funding the refurbishment of the V&A science laboratory, including the purchase of the Hirox HRX-01 digital microscope used for the digital microscopy carried out in this study.
