We were recently tasked with conducting an analysis of the historic interior finishes in a section of the North Office Building of the Pennsylvania State Capitol Complex. The Building was built and finished between 1928 and 1930, and based on the historic architectural design drawings, there should have been ornate spaces with decorative plaster and paint in the rooms where we were investigating.
When we started the investigation of the spaces, we sampled the obvious and not so obvious places. We took samples from walls that included the current wall fabric but made sure to get the plaster beneath. We took samples high up in the room and down low. We made sure we got a couple samples from each wall of a room. We even crawled around, above the black iron and plaster drop ceilings (fitting through an access door in the ceiling that was literally only as wide as my shoulders and crawling in a space about 30 inches high), to find original decorative material.
We could tell early on that the current wall covering was not original because there was a substantial build up of paint layers below it in some rooms, painted directly on the plaster walls. We thought that possibly the painted decoration could have originally been painted directly on the plaster walls, though buildings of this scale, and especially from our experience, in other buildings in PA's Capitol Complex, there should have been canvas on the larger sections of walls.
Some of the wall samples, that were reviewed under microscopic analysis, showed evidence of an adhesive between the earliest paint layer and the plaster substrate, evidence that an earlier wall covereing had been removed, leaving only traces of adhesive. The image below is of a sample taken from the wall surface above the original chair rail. The walls above the chair rails did not originally have canvas on them.
We searched through historic written documentation in the PA State Archives and discovered what we had already surmised: that c. 1950, the spaces were scoured clean of most of the historic fabric and decorative plaster ceilings. The drop ceilings were added at this time to hide the air conditioning equipment. The original wall fabric was removed during this "upgrade", then re-painted directly on the plaster in some rooms, or new fabric was added in other rooms and it was painted. The c. 1950 demolition crew were pretty thorough when they removed the orignal material. We searched everywhere for any original wall fabric and found none, until the drop ceilngs came down.
Once the c. 1950's drop ceilings were removed for asbestos abatement we were able to see and gain access to more areas of walls above those none original ceilings. We were able to look in the nooks and crannies above the drop ceilings that had essentially become time capsules for the orignal finishes and fabric and also of the evidence of the c. 1950 workers haste removing them. Remnants were left were it was more difficult and time consuing to remove them than it was worth.
Small fragments of canvas were left, stuck under original picture rails and picture rail anchors, in some spaces that were inaccessible when the drop ceilings were in place. Other fragments were left in corners of the room where their orignal adhesive held them tight.
It only really took one sample, though we reviewed all of the orignal canvas evidence found, to add that missing piece of the decorative puzzle. One sample had the known original, upper wall color, dripped over the original paint color on the canvas.
When conducting historic finishes analysis it pays to not only think like a scientist, by conducting random sampling of all elements, but to also think like a decorator, targetting areas where decorative elements and/or original historic fabric should be. In a way it is our job to reverse-engineer the original decorator's or architect's way of thinking.