25 years ago my wife and I purchased a house we estimate was originally built around 1835. Originally it was a four room farm house (two upstairs and two downstairs). We have finally gotten around to redoing one of the original downstairs rooms and the first thing we wanted to do was to get rid of the old lead paint. The woodwork is quite intricate. The window casings and window sashes we stripped completely down to bare wood and remounted the old glass and put on new paint. The baseboard, since it had a large flat surface, I decided to sc**** down. About 6 layers of paint pretty much 'popped' off with a sc****r. The first layer is a dull gray and looks almost like plaster. My question is - Was it common to use a plaster like material to 'prime' the casings back in the early 1800's? The first photo attached is a shot of the baseboard prior to final sanding. The second is a shot of the window casing after the new paint finish but prior to re installation of the sashes. Thanks in advance.