I am testing two biocides (chemicals that kill biological growth) to see how well they clean headstones. The two chemicals are D/2 from Cathedral Stone and BioWash from Prosoco. Both products claim to continue cleaning after you have cleaned and rinsed the stone. Both also state you can apply to the stone and leave it without scrubbing or rinsing and just let the chemicals do the work. This method would take longer to get the desired results, but would allow for some stones that may be too delicate for scrubbing to be cleaned to some degree. This test was conducted at Mullikin Cemetery in Nineveh Township, Johnson Co., IN.
Chemical treatments were applied June 26, 2010.
This first image is of a marble tablet moderately covered in biological growth. The left side of the stone was treated with concentrated D/2. It was sprayed on a dry stone and left alone. The right side was treated in the same way with BioWash, There was no scrubbing or rinsing.
This photo is the same stone four days after treatment.
While it is not yet completely clean, each chemical has started to kill the biological growth
Here we see the same stone 16 months after treatment. (Photo taken Oct. 29, 2011) Except for the bit of dirt where some of the blue tape had been this stone looks nearly as white and clean as it did new and it was done without risking damage to the stone using more aggressive methods.
This next stone was done the same as the previous with the only difference being the mix ratio of the chemicals. With the previous stone a concentrate was used, in this next test a 50/50 mix of the chemical and water was used.
Again, not yet clean, but killing the growth.
The next stone was treated with a 50/50 mix of D/2, scrubbed well and rinsed. The second picture is four days after cleaning. After four days there is some noticeable difference.
This stone had a 50/50 mix of BioWash and water, was scrubbed and rinsed.
In a separate test I cleaned a marker from Nay-Tremain Cemetery in Nineveh Twp., Johnson Co., IN. I sprayed a 50/50 mix of D/2 and water on a dry stone, let it set for a few minutes and then sprayed with a small amount of water and scrubbed for several minutes, then rinsed.
The first photo was taken June 6, 2010, the second about a week later and the third on July 1, 2010.
This stone was treated in the same way at the same time as the previous example.
Summary: At this point it seems to me that D/2 and BioWash are fairly equal cleaning-wise.
Although these chemicals wont always get a marble stone as white as it was new, they will clean the biological growth from the stone without removing the top layer of stone which can be the case with cleaning methods that employ the use of power tools (pressure washers, drills with wheel brushes…)
