Update: Alki Statue of Liberty brick-cleaning quest

David Hutchinson from the Seattle (Alki) Statue of Liberty Plaza Project sends an update on the “brick legibility problem” (previous report here): He says the city Parks Department has been investigating methods for “safely removing the calcium deposits that have formed on about 100 of the 1,500 inscribed pavers.” The photos at left show the results of a white-vinegar cleaning method that was tested – for spot-cleaning, it looks “encouraging,” but an evaluation by a professional cleaning company subsequently suggested it wouldn’t be appropriate for the large-scale plaza cleaning Parks wants to do initially. He explains, “It is not possible to use many of the standard cleaning methods for ordinary masonry products in this situation due to the nature of the engraved inscriptions.” So the tests continue – as do the sales of additional pavers (through 12/31/08; order info is available at sealady.org) to be placed next spring or summer, probably “in the east and west paths and in the brick landings of the stairs.”

cjboffoli October 23, 2008 (7:45 am)

The problem might be that the deposits aren’t just calcium but calcium silicates which are harder to remove. Vinegar is a good, low impact choice considering this site’s proximity to the ocean, but it is unfortunately not strong enough. You might look into a commercial product called “Noskum” (if you can get it within budget) or “CLR” which are both phosphate-free.

Jo October 23, 2008 (12:31 pm)

The professional cleaning person said above: “It is not possible to use many of the standard cleaning methods for ordinary masonry products in this situation due to the nature of the engraved inscriptions.”
What is the nature of the engraved inscriptions that makes this so different? Does it have to do with the environmental impact on the area?
Also, what responsibility does the brick company, Kenadar, have in this? Are they being at all helpful with this problem, or is it falling on Parks to come up with a solution?

David Hutchinson October 23, 2008 (5:55 pm)

Jo – Thanks for your interest.
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The inscriptions are first sandblasted into the pavers and then filled with “black epoxy grout”. This technique was chosen over the use of black paint as it was recommended for high traffic areas. You can’t clean the inscribed pavers the way you could pavers with no inscriptions – the standard acid treatments could irreparably damage the black grout. These pavers also can’t be pressure washed.
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Kenadar has been very helpful. They sent 2 representatives to investigate the problem at a meeting held at the Plaza on October 2nd which was mentioned in the WSB – https://westseattleblog.com/blog/?p=10942#more-10942 . At that meeting it was concluded that the issue was not with the engraving but with mineral deposits on the surface of the pavers obscuring the inscriptions. As this is an issue of maintenance, Seattle Parks & Recreation has taken the lead in researching the problem. Kenadar has asked to be updated on the results of this research and has agreed to “be responsible should any deficiency be found in the engraving work”. They also clarified some of the questions on future maintenance of the pavers that will be very helpful to Parks & Recreation.
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This problem is limited in scope – approximately 100 of the 1503 inscribed pavers are affected. I realize that this is small consolation if your brick is one of those 100. It is also limited physically to 2 distinct regions in the Plaza. Each of these bricks has been photographed to document the problem
The Seattle Statue of Liberty Plaza Project and the appropriate parties are aware of the issue and are working to find the best solution; one that will clean off the mineral deposits without damaging the inscriptions.

Jo October 23, 2008 (8:26 pm)

Thanks, David.
I never doubted that the problem was being addressed.
I guess it’s just puzzling why only 100 of the total engraved bricks have this problem.
Is there any idea why the mineral deposits formed in the first place?
Just curious.

David Hutchinson October 23, 2008 (11:45 pm)

Jo,
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From what I have been told and read, mineral deposits are common on masonry products and result from the chemical interaction of the concrete and moisture. Minerals leach to the surface of the bricks and some deposits such as the “efflorescence” (the white substance that appeared soon after the bricks were installed) weather away over time – http://www.lmblockrockpatio.com/mysitelmblock/paverfaq.html. The deposits that are obscuring the inscriptions are different and seem to be more resistant. Why these particular bricks are exhibiting this problem is a question Parks is trying to answer.
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What is known is this – the bricks affected are clustered in 2 specific areas of the plaza and the problem seems to only occur on the 4×8 inch bricks in those 2 areas.

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