A harder replacement is not automatically a better repair

A fictional restoration project involves an old mineral facade with localized salts, a history of water entry and several original decorative layers. A proposed replacement coating is harder and less vapor-permeable than the existing finish, but its compatibility has not been assessed. The team has not yet established which original layers should be conserved or which moisture routes remain active. A contractor argues that the most durable-looking product will make further investigation unnecessary. This classroom exercise removes no historic material and approves no chemical treatment. Review the difference between isolated product properties and performance of the existing assembly, and identify how material evidence, exposure, conservation requirements and an accountable approved repair strategy affect the decision.