This article by HM Southgate has been extracted, revised, and/or copied from Weekly Philatelic Gossip

Stamp Booklets
Experimental Interleaves
April 6, 1940

by
HM Southgate, President
Bureau Issues Association, Inc.

FROM TIME TO TIME the Bureau of Engraving and Printing has experimented with the material used for interleaves in our stamp booklets but the waxed paper used with the first issue back in 1900 still holds its own.

The first experiment of which I have record was made in 1915. Somewhere in some old notebook there lie concealed notes made when I found a few 25c two cent books with a deeply embossed white interleaf of waxed paper that looked as though it had been run between knurled wheels similar to those that were used to grill our earlier postal issues or which occasionally show up on our current issues when a new tension roller in the Stickney perforators is screwed down so hard that the tops of the knurls show up, cutting the gum or even striking through the paper as in the case of the "small pox" Stuart coils.

Across the center of each leaflet in two rows of small capitals, the top now being inverted, appears PAT. SEPT. 20, 1904. The records show that a lot of 396 books were made, doubtless from a trial lot of sheets supplied by the manufacturer. Dole, in his list, says that these fancy interleaves were used in booklet "10a" but it was type 10d.

The manufacturer of cellophane thought that booklets would be a good outlet for their new product and sent the Bureau a sample lot of sheets in the spring of 1928. This was used to interleaf a lot of 25c two cent books which my notes indicate were probably mostly destroyed and not sold with the regular stock. This booklet has the Post Office insignia on the front cover, 0.965 inches diameter, small model address form on the second page, 8 lines of admonitions as to how to mail your money, etc., on the third page and the ad of the Postal Savings System in 11 lines of text that you can deposit up to $2,500 (but not how to get it) if you are over 10 years old. Further, if you move you can "transfer between post offices without cost or loss of interest." This last quotation is probably the easiest means of cover identification as the privilege does not appear on later books. The panes are rotary press product with two diagonal breaker marks per stamp.

The price of the material prevented the adoption of cellophane as was the case with the patented paper. Wax paper interleaves served the purpose of preventing sticking pretty well but apparently there was some demand for something better as in September, 1928, some 3,500 to 4,000 books of 25c and 97c one cent, 73c one and two cent, and 25c two cent books were made up with glassine paper interleaves.

This glassine paper was very thin, 0.001 inch thick, as compared with 0.002 inch to 0.0025 inch for the normal wax paper. The surface is smoother and does not have the slightly greasy appearance of the wax paper.

Apparently there was little or no advantage gained by the glassine paper, while the thinness made it difficult to handle, the sheets of interleaves not slipping into position easily in the collating of the covers, panes and interleaves, so nothing came of that.

The cellophane lads had another whirl at the task of trying to get their product accepted. This time it looks as though they had furnished a thinner material in order to reduce prices as the July, 1936, experiments were with a 0.001 inch interleaf whereas the earlier cellophane was 0.00125 inch to 0.0015 inch thick. Some 30,000 of the 37c three cent booklets were made up and turned into the Washington post office stock, I know, going on sale at the Union Station and Navy Department branch offices and probably elsewhere. The covers are like those of the first 2c cellophane interleaved booklets except that there are only 10 lines of advertising of the Postal Savings System on the fourth page, there being no suggestion of transfer between offices without loss of interest.

There are variations in the interleaves of the earlier covers in the thickness, color, and finish of the waxed paper. This is to be expected during the 40 years we have had booklets.

However, the BEP started with a waxed paper and they still have it but from the above notes it is evident that they are willing to try to improve.

There is one interleaf change that has taken place. For 30 years, from the birth of the first "specimen" issued by Postmaster General CE Smith, an interleaf in front of the first pane of stamps has been part of the equipment of every well appointed book. Like an appendix it apparently served no useful purpose. It was in the way when you wished to remove stamps from the first pane and it cost some money but there it was and apparently no one could do a thing to omit it although the question of its utility was often raised. However, in February, 1930 on one of my periodic purchases of a sample of each type of book, to see what, if any, change had been made, I found the first interleaf missing in the 25c one and two cent books, the 49c two cent and the 73c one and two cent books and the leaf has never come back.

Taken from March, 1940, Bureau Specialist.