The glass in aged windows might be the very early 'plate' or 'broad' glass to 'crown' or 'cylinder'.[5] Aged glass is recognised by its imperfections ('ream') which lead to optical distortion. These strips are often appropriate for draught-proofing a window with casements but not sash styles.  Their ingenious well balanced https://angelinak814jkl7.spintheblog.com/36231178/5-easy-facts-about-sash-window-draught-proofing-described