Special Report
Rules of Removal, Chemical Stripping and Historic Masonry

From D+D Print, May 2013

by Courtney Murdock, AMT Lab
	The author explains the process for removing coatings from historic substrates, specifically masonry.... (Login to read the full article)

Comment from Jon Cavallo, (7/5/2013, 8:58 AM)

I suggest that Ms. Murdock spend a little less time lecturing and a little more time attending state-of-the-art conferences to see what technologies are now available for surface cleaning involved in restoration of historic structures. For instance, lead and other heavy metals can be reliably detected using nondestructive instruments without disturbing the existing coating layer. Her photos in the article (particularly of the US Capitol project) demonstrate the environmental mess that can be created by combining chemical strippers with high-volume water cleaning. Additionally, please note the construction "white-hats" standing in close proximity to the water cleaning operation are most assuredly breathing in the paint-debris laden water mist produced by the water cleaning operation.

Comment from Tom Schwerdt, (9/3/2013, 11:12 AM)

Why not dry ice blasting? When I saw a demonstration on a historical bridge, it worked very well (certainly faster and cleaner than the chemical stripping) - with no damage to the underlying concrete. Of course, old mortar and brick is a lot softer than structural concrete. The chemical stripper photos shown above show a lot of debris and water just being released into the environment, without even tarps on the ground to try and catch debris for proper disposal. Also, are you being sure to test EVERY layer of EVERY paint for lead? It was not mentioned in the article. Just dabbing the topcoat is not sufficient to determine if lead is present in lower layers.

Comment from M. Halliwell, (9/4/2013, 11:02 AM)

A lot has changed in the last 15 years (since some of the used photos). Locally, neither of the rinse / water blasting projects in the photographs would have been permitted to proceed without containment for the debris and wash water as well as better protection for the observers (whatever their roles).

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