Analyze an existing historic mortar sample (acid digestion and sand gradation/color matching) to inform a repointing mix specification

Steps

1. Extract multiple mortar samples from protected, less-weathered locations on the wall (e.g., under overhangs) to get a representative unweathered reading rather than surface-degraded material
2. Send samples to a qualified materials-testing or preservation mortar-analysis lab rather than attempting acid digestion in the field without proper safety controls
3. Have the lab perform acid digestion to separate the aggregate from the binder and determine the approximate binder-to-sand ratio by volume
4. Have the lab characterize the recovered sand's gradation, color, and mineralogy under magnification so a replacement aggregate can be sourced to match
5. Cross-reference the binder residue characteristics (lime vs. natural cement vs. early portland) against the building's known construction date to sanity-check the lab's binder identification
6. Use the analysis output as the basis for a trial mortar mix, then cure and compare sample batches against the original before finalizing the repointing specification