Bk 78 Pane Widths - Why Do They Vary

Attached are part scans of three panes from the BK 78 booklet.







The variations in the width of the margins is documented in Unitrade without any explanation as to how they occurred.

The margin on the top pane is 9mm wide and the overall pane width is 91mm
the corresponding numbers for the other illustrations are
15mm/96mm for the second pane
20mm/100mm for the third (lower) pane

The lower pane shows 2mm of tagging at the left edge and also half of a perforation hole. These must have come from another booklet pane on the left of this one.

I am curious as to the layout of the printing plates and also how the booklet panes were separated to produce these widely differing margins. Any references to information on this booklet will be much appreciated.

Thanks for the pictures. Now we understand the issue.

Are all three from the same booklet?
The top one is shifted down. the middle is shifted left and the bottom is normal.

All are from BK 78 but obviously different booklets. I cannot see that the slight shift in the relative positions of the stamp to the perforations has any bearing on the width of the margins. I assume that these are the normal production variations.

AQ

That is great. Now All I want is an answer

AQ

Dumb question but are you referring to stamp margins or the tab at the left of the pane that holds the pane in the booklets?

This booklet, like most of the ones with definitive stamps issued from about 1968 to 1985 (and a few 50c booklets beyond 1985), was printed by British American Bank Note Co. (BABN) on its Goebel web-fed press. The web-fed press prints stamps on a large roll of paper, not individual sheets, and also perforates the stamps and, for stamps issued in panes, cuts the large roll into individual panes.

The stamps in BK78 are printed by a combination of engraving and photograuvre. The printing cylinder for the engraved colours contains 36 rows of stamps around its circumference. One engraved cylinder can print up to three colours. The photogravure cylinders (one for each colour, and one for the tagging) contain 24 stamps around their circumference. For the stamps in BK78, the stamp width is laid out along the axis of the cylinder and the stamp height is laid out around the circumference.

The production of the 1967 Centennial booklets printed by BABN is explained in an article on Centennial stamp production in the Robin Harris Centennial Definitive Series 1967 - 1973 catalogue. The cylinder layout for BK69 is illustrated on page 79 of the catalogue. The production of BK78 is similar, except that the format of the stamp designs is portrait and the designs include photogravure colours whereas the Centennial definitives were landscape and had only engraved colours (except for those that were tagged).

The number of booklet panes along the axis of the cylinder is likely four (but possibly six). Referring to the article on Centennial definitives, the large roll is slit and rewound into smaller rolls containing a pair of panes along the axis of the roll. The smaller roll is put into a "booklet machine" that prints the cover stock, also in a continuous roll one booklet pane wide, glues the roll of stamps to the cover stock, and guillotines the roll of cover stock + booklet panes into individual booklets. If the roll of booklet panes was two panes wide, the roll is slit during the operation, one side is glued to the cover stock and the other is rewound and subsequently re-fed into the "booklet machine".

All this to say that that your booklet varieties, Anthraquinone, were produced because the slitter that separated the large roll into smaller ones was misplaced. In fact, for your example showing part of the tagging and perf hole of an adjacent booklet, it looks like one slitting wheel was somehow completely disengaged. This is a rather nice variety because it shows exactly what the spacing was between one pane and the adjacent one to the left.

Admcol

Thank you very much for that clear explanation. It was just what I was after.

AQ