7.4×
+118% recall vs. cleaned facades
Average legibility lifespan of an incised wall mark
Scratched and burnt traces persisted in field recall for 7.4 years on weathered plaster, against 1.0 year for repainted surfaces. The scar carries the memory; the clean wall forgets.
Persistence by surface condition
Incised on aged plaster7.4 yr
Burnt / charred trace5.1 yr
Painted-over surface2.3 yr
Repainted clean facade1.0 yr