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Scott 637 "Breaking" Lines Of The Rubber

 
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Pillar Of The Community

Romania
513 Posts
Posted 10/04/2022   02:06 am  Show Profile Bookmark this topic Add cupram to your friends list Get a Link to this Message
I am not familiar with the Scott catalog and it was difficult to find and identify this strip of 4 stamps
Perforation is 11 x 10.5 and dimensions 19.5 x 21.5 mm.
The stamp width of 19.5 mm and the vertical rubber break lines led me to the conclusion that it is Scott 637- rotary press with impressions placed sideways on the curved plates.



I have no information about the wide and horizontal line that appears on the rubber (I suspect that when the rubber breaks, there are pressure rollers that press on the cylinder with the role of keeping the sheet firmly stuck to the cylinder and leave a trace perpendicular to the breaking lines of the gum)





Is my assumption correct?
Is the position of these pressing rollers known? how many are? in which row/column of the sheet do they appear?
On the first stamp in the band there are some white dots and a break in the internal oval line.
Is it a plate error or just a printing error (dirty plate)?

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Pillar Of The Community
United States
3019 Posts
Posted 10/04/2022   7:40 pm  Show Profile Bookmark this reply Add hy-brasil to your friends list  Get a Link to this Reply
The horizontal line is called a gum breaker. It was impressed to try to keep panes from curling in storage and is perfectly normal and common. This type/style appears once per stamp in every pane in this case. There are other versions where there are two horizontal gum breakers per stamp.

The white spots in the stamp are either due to a dry print or ink peel where ink did not stick perfectly to the paper. This is quite normal and common also. They needed to print millions of these stamps and trivial flaws like this were tolerated.
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Pillar Of The Community
Romania
513 Posts
Posted 10/05/2022   02:44 am  Show Profile Bookmark this reply Add cupram to your friends list  Get a Link to this Reply
Thank you, @hy-brasil.
From a previous post (for Canadian stamps, I think) I understood that the gum break lines are the vertical ones (about 14 marks per stamp).
I suspect that the lines of breaking the gum are made between 2 cylinders - one smooth and one profiled with the reverse curvature of the paper strip compared to the curvature during printing.
The problem is the appearance of the wide horizontal mark on the gum, perpendicular to the vertical break lines; has this mark been observed before?
I googled "Types of rotary printing machines used in 1927" but it would be very helpful to know what machine was used for these stamps.
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Pillar Of The Community
United States
3019 Posts
Posted 10/05/2022   04:07 am  Show Profile Bookmark this reply Add hy-brasil to your friends list  Get a Link to this Reply

Quote:
The problem is the appearance of the wide horizontal mark on the gum, perpendicular to the vertical break lines; has this mark been observed before?

That is exactly what is called a gum breaker, not what you are assuming is happening with the gum lines. This began being used around this time and was still being used much later. It is ubiquitous. You just haven't seen enough mint US stamps from this time period yet.
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Pillar Of The Community
Romania
513 Posts
Posted 10/05/2022   05:02 am  Show Profile Bookmark this reply Add cupram to your friends list  Get a Link to this Reply
Thank you, @hy-brasil.
I now understand what break line gum is.
I do not have MNH stamps from this period and I would wrongly assume that the vertical lines appear during printing and not that this is how the gum was applied.
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Pillar Of The Community
United States
3019 Posts
Posted 10/05/2022   6:22 pm  Show Profile Bookmark this reply Add hy-brasil to your friends list  Get a Link to this Reply
Yes, the stripes were exactly how the gum was applied at the printers for the US rotary press definitive issues. This gumming method did not apply to flat plate printed commemoratives of the same time period. Multiple stripes do not appear on mint rotary press coils, either. Understand that there is no direct connection between the way the gum is striped and gum breakers.

More on gum breakers:
https://www.kenmorestamp.com/gum-br...on-us-stamps
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Edited by hy-brasil - 10/05/2022 6:22 pm
Pillar Of The Community
Romania
513 Posts
Posted 10/06/2022   12:54 am  Show Profile Bookmark this reply Add cupram to your friends list  Get a Link to this Reply
@hy-brasil, excellent answer and thanks for the address of a new site for my archive.
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