Clarifying Misconceptions: The Use of Wet & Forget in Historic Headstone Conservation

Discussions within the cemetery preservation community have featured inaccurate claims regarding the suitability of Wet & Forget for cleaning historic headstones, often citing a study conducted by the National Center for Preservation Technology and Training (NCPTT). A closer examination of the facts reveals important distinctions regarding product formulations, study parameters, and cost-effectiveness.

1. Clarifying the NCPTT Study Finding

Critics frequently cite the NCPTT study to argue against using alternatives to D/2 Biological Solution. However, several critical details are often misrepresented:

• Product Exclusion: Wet & Forget was not tested in the NCPTT study primarily because it was not commercially available at the time of the research. (Prosoco’s ReVive, formerly known as BioWash, was similarly omitted.)
• Broad Applicability: The study did not mandate D/2 Biological Solution as the only appropriate cleaner. Rather, it concluded that products containing quaternary ammonium compounds are suitable for biological removal.

2. Chemical Composition and pH Balance

When selecting a biocidal cleaner for historic stone, professionals generally look for a pH level as close to neutral as possible to minimize potential long-term adverse reactions:

• Neutral Baseline: Pure water has a neutral pH of 7.0.
• Wet & Forget: Features a pH range of 7.5 to 8.0, making it slightly alkaline.
• D/2 Biological Solution: Features a pH range of 9.0 to 10.2, making it moderately alkaline.

In terms of pH proximity to neutral, Wet & Forget offers a very favorable profile. Furthermore, long-term practical field testing over several years has shown no apparent chemical damage to stone substrates, with performance results comparable to both D/2 Biological Solution and Prosoco ReVive.

3. Economic Practicality and Accessibility

Some opposition to readily available retail products stems from a traditionalist mindset that equates commercial availability with lower quality. However, from a practical standpoint, project budgeting requires evaluating cost-efficiency, particularly for volunteer organizations or small-scale preservationists:

• D/2 Biological Solution: Retails for approximately $50 per gallon. It is sold ready-to-use and is generally not diluted.
• Wet & Forget Outdoor: Retails for approximately $30 per gallon as a concentrate. One gallon yields six gallons of usable cleaning solution.

To achieve six gallons of working solution, the comparative costs are stark: approximately $300+ for D/2 versus $30 for Wet & Forget.

Conclusion

Wet & Forget, D/2 Biological Solution, and Prosoco ReVive are all viable, effective products for removing biological staining on historic grave markers. When choosing between them, preservationists can confidently consider factors such as formulation chemistry, practical performance, and budget without compromising conservation standards.