Machine 10p Unusual Printing Method 1980`s-Info Please?

Revisiting my collection to add some new material I came across this Machin 10p mint strip/part sheet etc. with two used setenant triples plus a mint triple as shown - stamp/centre blank/stamp, that I`d stored with some booklets/covers some years back.
I just about recall that this was a new/trial print method but thats all I have.
can others fill in some details for me. The stamps are type1 with two side bands which extend 5mm onto the central blank strip.
Any input would be a great help-with thanks


*** Moved by Staff to a more appropriate forum. ***

Rather than "triples"
I have always referred to them as "Interpanneau pairs"

The blank portion is the gutter that separates the two panes from the plate.
Can be vertical or horizontal.

Spink Swiss Interpanneau pair.

Are these Phos Paper ?

Take no notice of the following,
I am practising reading Gibbons

Are these X886 (1976) or X939 (1979) X940 (dull orange) =type 2? (all std perforation) 2 bands
10p Photo, Orange-Brown
from "sheets"

What routine do the specialists employ,
to arrive at the correct issue?

It is a normal photogravure 10p with two B3-phosphor bars. What you have is from a sheet that was printed in two panes with a gutter margin.
I think it is from Harrison's Jumelle Press. That will be in the SG Specialised Catalogue.

As for the paper, I expect fluorescent-coated paper, certainly not phosphor-coated. X886.

These stamps were actually printed on the Chambon press, rather than the Jumelle. They are the only definitives of this design that exist in gutter pairs.

The "non-specialised" SG number is indeed X886, but this incorporates two specialised numbers: U184 printed on fluorescent coated paper with two phosphor bands, and U185 printed on phosphorised, fluorescent coated paper but still with two phosphor bands. U184 comes from cylinders 7 and 9; U185 from cylinders 7, 8 and 9. The two panes in each printing were both "no dot".

Source: SG GB Vol.4 Specialised, QE2 decimal definitives, 8th edition, 1996.

Phil

That was my doubt whether it was Chambon or Jumelle that had the gutter.

And indeed, part of the printings were on experimental phosphor-coated paper. Pricewise, there is very little difference. Connoisseur quotes 40p and 50p, respectively. Deegam has them the other way around.

Thanks Phil
Can you explain the "no dot" please?

The cylinders used to print the photogravure issues had a cylinder number in the sheet margin. Normally, the definitive stamps were printed in double panes. Each pane had a cylinder number in the margin (mostly to the left of stamp 1 in row 18).

The left pane (or only pane from single-pane cylinders) had the cylinder number. The right pane had a dot behind the cylinder number. Below are cylinder blocks with cylinder D1 - dot and D2 - no dot.



The right pane of cylinder D1 (D1 - no dot) had the famous missing £-sign and was withdrawn shirtly after the stamps were issued.

But with the 10p Chambon printings, both panes showed the cylinder number without a dot.

Thank you both, fascinating.

These 10p stamps had a horizontal gutter separating the two panes. As OP's picture shows, vertical gutter pairs exist.

Normally, the double-pane sheets were printed with a vertical gutter. These primary sheets were cut in two counter sheets through the vertical gutter.

NSK: in the OP's photo, the stamps on the top row have been turned onto their sides. All the stamps shown have a horizontal gutter which separated the two panes.

@flip138: as I wrote, Horizontal gutters for the 10p Chambon printings, making vertical gutter pairs.

The gutter pairs remain vertical, whether or not shown sideways,

NSK: we are in agreement. I misinterpreted your sentence "As OP's picture shows, vertical gutter pairs exist." as implying that horizontal gutter pairs might also exist. Apologies.

Best regards

Phil

What is the difference between fluorescent-coated and phosphor-coated?

answer: Whether a fluorescent or phosphorescent agent has been added to the paper coating.

Fluorescence is a reaction caused by an optical brightening agent or a fluor. This has an immediately visible reaction under UV-light. Long-wave uv-light tends to be required.

Phosphorescence is the reaction of phosphor, normally mixed with an activator to uv-light. This causes an afterglow. It depends on the phosphor ink used whether it reacts to short-wave, long-wave, or both uv-lights. In the case of Machins from the 1990s onwards, the phosphor also has a fluorescent agent added giving a blue or yellow colour.

If you take a Machin from the 1970s with phosphor bars and you hold it under uv-light, you, likely, will see the bars turn dark. This is the phosphor absorbing the uv-light. Only after you turn the uv lamp off, will you see the afterglow.
If you look at the white border between the bars, long-wave uv-light makes it appear whiter. That is the optical brightening agent causing a fluorescent reaction. If you turn the light off (in a dark room) that is what becomes dark.

I hope this makes sense. If not, after work, I shall post some pictures.