After Dr. Buck analyzed her samples from the colonnade columns, she discovered that the first, and earliest, layer on all but one of the five samples was a relatively thin layer of white plaster.  In several of her samples she also found that one or two layers of whitewash had been applied over the base layer of white plaster.  Because these early plaster and whitewash layers were found under the coating of tan sanded paint, it became vital to know when the tan paint dated to.  If the tan paint was found to date to the 1840s, then the whitewash and plaster that was located under it would most likely date to when President Madison owned Montpelier.