New Technology For Renovating Historic Lighthouses
By Sue Clark on Jul 14, 2008 in Featured 
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Dry Ice Blasting - Cheaper and Safer for the Environment
Earlier this year, Split Rock Lighthouse (Minnesota) was closed for renovations and painting. Normally, when lighthouses and other historic structures are repainted, the removal of the previous outer coating and its attendant cleanup is the most expensive part of the process, involving the use of sandblasters or other grit based removal systems. And with the attendant cleanup, the costs rise exponentially. What was unique about Split Rock, is that a relatively new technology that came into being in the late 1980s was used rather than the old fashioned, and damaging methods.
Yes, damaging, because the gritty medium usually used to blast away the old paint cannot be completely removed. It adheres to the substrate and will cause early peeling of the new covering, leading to an earlier than planned repainting. Harsh solvents used to remove grit contamination are neither good for the environment nor good for our historic buildings. So it was with great interest I read of Split Rock’s use of dry ice as a blasting medium.
A Recent Technology
The use of dry ice pellets for cleaning is a young technology developed in the mid 1980s as a safe and environmentally responsible industrial cleaning method. It’s used to clean everything from circuit boards to concrete to mold removal. Dry ice pellets do not leave a residue, nor does it need cleanup afterwards, as sand or other grit based pellets require.
Dry ice pellets are made by taking liquid carbon dioxide (CO2) from a pressurized storage tank and expanding it at ambient pressure to produce snow. The snow is then compressed through a die to make hard pellets. The particles are then propelled at supersonic speeds to clean a surface. The micro-thermal shock, caused by the dry ice temperature of -79º C, the kinetic energy of dry ice pellets and the air pressure break the bond between the coating and the substrate. It pops off the coating from inside out and the air stream removes it from the surface. The pellets vaporize, so the only cleanup is the original coating.
Environmentally Safe
Although carbon dioxide gets a bad rap in the press, it’s actually necessary to life. In fact, our own breathing is regulated by the amount of carbon dioxide in our lungs, not by oxygen. However, to allay fears of the global warming alarmists, the carbon dioxide used in the production of dry ice pellets is obtained as a byproduct of other industrial processes, that is, it is made from reclaimed CO2. It does not produce CO2 or add CO2 to the atmosphere and therefore does not contribute to the so-called greenhouse effect.
For further reading about this extremely safe method for lighthouse restoration, below are some further resources. If your group is involved in any restoration, I’d highly recommend this method, as a cost saver, environmental saver and time saver. Not to mention the protection of our buildings. If this method can be used to clean fire damaged books, you can be assured that there will be no damage to the underlying structure.
Further reading
Photo credits:
- Split Rock Lighthouse by Boodie131. Some rights reserved.
- Split Rock Lighthouse at Sunset by Elm Studio. Some rights reserved.
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More About Restoration Challenges
- Lighthouse Restoration Can Be a Challenge
- Lighthouses - Self Destructing Bricks
- New Technology For Renovating Historic Lighthouses
