As a researcher on Ronald Reagan鈥檚 abortive 鈥淪tar Wars鈥� anti-ballistic missile programme in the 1980s, Ray Schaefer had to learn all about how laser beams interact with surfaces. Now he is applying his extensive knowledge to a very different task: making old houses safe for children.
Instead of trying to blast holes in Soviet missiles, powerful pulses from a new type of light source Schaefer has developed can vaporise lead paint that might poison incautious youngsters.
Once widely used in housing, lead paint is now banned in most countries because of its toxicity. However, it is still be found in the US in many houses built before 1978, putting children at risk of ingesting lead from dust and by chewing painted objects. Removing paint by scraping or by dipping items in paint remover is costly, time-consuming and creates extra contamination risks.
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Another method would be to vaporise paint with intense pulses of light lasting less than one-tenth of a millisecond while mechanically sucking away the resulting fumes. Lasers strip paint from aircraft in this way, but such systems are far too expensive for domestic paint removal.
鈥淎nother method would be to vaporise paint with intense pulses of light鈥�
So Schaefer, founder of Phoenix Science and Technology of Chelmsford, Massachusetts, has developed a variation on a xenon arc lamp that he calls a surface discharge lamp. Instead of firing pulses through a tube filled with xenon gas, as a xenon flashgun does, Schaefer鈥檚 device has a ceramic tube surrounded by xenon running between the electrodes. A discharge current travels along the surface of the ceramic tube, producing a highly localised, high-energy flash of a duration and intensity that he has tuned for effective paint removal.
In tests the idea works well, Schaeffer reports in the journal Environmental Science and Technology (DOI: 10.1021/es061328g). His next step, for which he has already received a grant, will be to build a truck-mounted version of the paint-zapper to test in municipal renovation projects.
