3.1 Choice of Cleaners

The most important variable in the study was the choice of cleaners. The team investigated fifteen possible cleaners for inclusion in the study. Possible cleaners are shown in Table 1. The chemical action of these cleaners includes acids, bases, alcohols, chelating agents, solvents, surfactants, and bactericides.

Acids and bases are strong chemical cleaners that work on the basis of the pH of the product. Products such as the Stone Kleen contain ammonium bifloride that easily converts to hydrofluoric acid, a strong acid that can chemically etch and potentially damage the surface of a stone. On the other end of the spectrum is the Kandu product, a low foaming cleaner containing sodium hydroxide, a basic compound.

Alcohols work on the basis of dissolving dirt and grease. They tend to evaporate quickly and are less likely to leave chemical residues. They may be one component of a multicomponent cleaning system. Four of the products, including World Environmental group Marble Cleaner, incorporate alcohols into their formulas.

Chelating agents work on the premise that the cleaner will bind the dirt or grime to itself in order to remove the soiling. Some products containing chelating agents include Stone Quest, Zep-A-One, and World Environmental Group Multi Surface Cleaner 1000.

Solvents work similarly to alcohols in that they dissolve the soiling and may be a component of a more complex cleaning system. Only the product GK125 is listed as a solvent-based cleaner. Solvents are incorporated into some of the other cleaning systems.

Surfactants are wetting agents that lower the surface tension on a liquid allowing for easier spreading. Surfactants also allow grease and oils to be diluted and mixed into water and washed away. They are commonly found in cleaning detergents. Stone Quest, Multi Surface Cleaner 1000, Zep-A-One, World Environmental Group Marble Cleaner, D/2, Kodak Photo-Flo, and Kodak Hypo Clear all contain surfactants.

Bactericides are chemicals that kill bacteria and are commonly found in disinfectants, antiseptics, or antibiotics. One group of bactericides contain cationic surfactants such as quarternary ammonium cations. The D/2 product is an example of a bactericide containing quaternary ammonium cations. Another group of bactericides contain strong acids. Stone-Kleen is an example of a strong acid bactericide.

The five cleaners chosen for inclusion in the study are shown in Table 2. The team wished to include cleaners that were environmentally friendly, user friendly, and were unlikely to damage the stone. Cleaners containing strong acids and bases, such as Stone- Kleen and Kandu, were eliminated on this basis. Daybreak was the most commonly used cleaner within the NCA, and thus was included in the study. H2Orange Grout Safe was chosen to represent an acidic cleaner containing citric acid. D/2 Antimicrobial cleaner was chosen as a bactericide and cleaner. The team felt that the two products by the World Environmental Group were very similar in nature and relied on surfactants and chelating agents. The World Environmental Group Marble (WEG Marble Cleaner) was chosen for inclusion in the study. The final cleaner selected was the Kodak Photo-Flo because of its common use in the cemetery cleaning world. Table 3 shows the range of pH values found for the products chosen for the study.