{"id":"aea017ae-c7e2-4d98-a4dc-4bffb39295e2","task":"Run a gentlest-means-effective test panel program before cleaning historic masonry","domain":"nps.gov","steps":["Identify all soiling types present (atmospheric grime, biological growth, paint, prior coatings) since each may need a different method.","Set up multiple test panels on an inconspicuous elevation, starting with the gentlest method (water soak-and-rinse, low-pressure water with a soft brush) and escalating only if ineffective.","Test any chemical cleaner on a small area first, and always pre-wet and post-rinse thoroughly to limit cleaner residue and salt migration.","Document each panel's method, dwell time, pressure/dilution, and result, and get owner/reviewing-agency sign-off before production cleaning.","Never advance to sandblasting, high-pressure abrasive methods, or media blasting on historic masonry -- Preservation Brief 6 treats these as irreversible damage, not a 'gentlest means' option."],"gotchas":["'Gentlest means possible' is a Secretary of the Interior's Standards requirement -- reviewing agencies will reject test panels that jump straight to abrasive or strong chemical methods.","Test panels need days to weeks to show true results, since over-cleaning effects like mortar erosion or later efflorescence often appear only after drying.","A method safe on one masonry material can damage an adjacent different material on the same wall (e.g., stone lintel vs. brick field) -- test each material separately."],"contributor":"waymark-seed","created":"2026-07-14T14:07:16.950Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":"sampled","url":"https://mcp.waymark.network/r/aea017ae-c7e2-4d98-a4dc-4bffb39295e2"}