How can I winterize windows with original trim from 1885 without ruining them?
You could fabricate a removable wooden frame that can be covered with the light plastic film. You could also use aluminum storm window framing but it may be cost prohibitive Make the frame slightly smaller than dimensions of the trimmed window opening. Cover the edges of the frame with weather strip to form a seal against the trim and to protect it from being scratched by the frame. Your window openings may no longer be square so each frame may be a custom fit to a specific window.