General information about printing on TD6 presses

Introduction

In this article, we will first explain the printing principle on a TD6 press and then the way sheets of stamps are printed on such a press. We will also present the notion of phosphor band and the four types of such bands known for the stamp 0,50F Marianne de Béquet.

Printing principle on a TD6 press

A six-colour intaglio printing machine (TD6 press) is made of two printing blocks of three colours, various items for additional printings, a perforator and an output device, either in the form of sheets or in the form of booklets (cf. the article Preparation of booklets).

The first printing block is an indirect recess printing one. This first printing will have no relief (this block generally prints swaths of colour such as backgrounds). The form cylinder is engraved and the image is upright. After inking with cut touch rollers and wiping, the ink is deposited by pressure, with images back to front, on a transfer cylinder in soft plastic which, in turn, deposits ink by pressure in the face of the paper, as in offset. Printing is then dried in an infrared tunnel.

The second printing is direct line-engraving. The form cylinder is engraved, with the image upside down, to have a printing of the image upright. Inking is obtained by three hand cut touch rollers. A wiping roller removes excess ink to leave it only in the grooves of the engraving. After a second wetting of the paper, the form cylinder directly deposits ink by pressure of an impression cylinder, itself pressed by a counter-pressure cylinder. This printing is again dried and rapidly cooled on contact with hollow cylinders in which some cold water passes to create a thermal shock.

Stamps are then perforated by a comb. On a TD6 press, a comb is made of two horizontal rows of pins with the sheet of stamps width and of 11 side rows.
 

comb operation on a TD6 press

 

Phosphor bands (for printings with such bands) are then printed with some UV ink and immediately dried by an UV dryer. Several printing systems of these bands have been used, we shall return there farther.

Printer’s markings are printed in letterpress by a cylinder with the control number, the number of the plate used to print the sheet and the date.
 

basic diagram of a TD6 press

 

A rotating cutting cuts each sheet to let them overlap on a conveyor belt of reception where it only remains to stack them by packages of one thousand.

It is always possible to only use a single ink reservoir to produce a monochrome printing (which is the case for the stamp 0,50F Marianne de Béquet). In this case, the touch roller will not be cut.

The drying, to avoid mixtures of colours and spots, is a major concern throughout the run on a TD6 press. A TD6 press has an infrared dryer tunnel and paper passes four times in this tunnel:

  • Before printing: the paper undergoes a preheating to lose the maximum moisture. This operation, which causes an important shrinking of paper, allows to limit its dimensional variations during the drying of the indirect recess printing;
  • After indirect recess printing: the paper goes back in the dryer tunnel to dry ink and to avoid any maculation and mixture of colours during the direct line-engraving printing;
  • After direct line-engraving printing: this new passage allows to dry ink of the direct line-engraving printing and, thus, to perform the latest operations of sheet numbering, perforation and cutting;
  • After printing phosphor bands.

Finally, stamps, once printed, are sent as parcels of 1000 sheets, probably to one post office by department. For that purpose, the printing office of Boulazac printed labels which appeared on the sent parcels:
 

label affixed to the package containing 1000 sheets of the stamp 0,50F Marianne de Béquet (with phosphor bands)

 

Printing method of TD6 sheets

printing scheme for sheets on a TD6 press

Every tour of the gravure printing cylinder prints bottom up three 100 stamps sheets, numbered from 00000 (= 100 000) to 00001, separated by a stamp height gutter, in which the guillotining of sheets will be performed.

The first sheet (sheet A on the figure on the left) has an {{electronic mark}} ( R.E. in French) on the left of stamp location 91 (it is worth noting that electronic marks are hand-engraved on the gravure printing cylinder to allow the electronic tracking of the second printing and of the perforation after optical character reading. Being hand-engraved, they have different shapes and are at different locations from each other with regard to stamps. This enables philatelists to describe and to study them). Sheet B has no mark and sheet C has two fine red lines under the stamp location 100 (for some printings, the two red lines are located in the left corner; for other editions, the two lines are not inked. This information will be given in the section about the description of printings).

On the following figures, we show the three dated plate blocks of 20 stamps printed by a single turn of a gravure printing cylinder (i.e. three sheets with consecutive control numbers). One can see the two red lines of the cylinder AG on the dated plate block numbered 10913 and the electronic mark of the same cylinder on the dated plate block numbered 10911.

Dated plate blocks of 20 stamps number 10913 printed by the form cylinder AG. On mouse-over, an enlargement of the right corner of the sheet appears showing the two thin lines of the form cylinder AG.

Dated plate blocks of 20 stamps number 10912 printed by the form cylinder AG. This bottom of sheet has no particular mark.

Dated plate blocks of 20 stamps number 10911 printed by the form cylinder AG. On mouse-over, an enlargement of the left corner of the sheet appears showing the electronic mark of the form cylinder AG.

characterization of a form cylinder by its two red lines

Philatelists (cf. SOCOCODAMI's books for example) used to describe printings thanks to gravure printing cylinders and to characterize these cylinders by means of the two red lines appearing in the right corner of one in three sheets of stamps. We would like to recall here how these cylinders are characterized.

The two red lines are respectively called S (for Superior) and I (for Inferior). They are defined by the distances in millimetres between each of these lines and the bottom of the stamp situated just above (cf. the opposite image). For example, cylinder T is described on SOCOCODAMI's book on Béquet by:

S = 4 3/4, I = 5 3/4, short lines to the right.

The control number is located under stamp location 91, the plate number TD6-x (x = 1 to 7) under stamp location 95, 96 or 97 and the printing date under stamp location 100.

A 100 stamps sheet measures approximately 285 mm high and 230 mm wide. Side margins are white and pinked, high and low margins white and vertically perforated.

Phosphor bands

Luminescence is the property that have certain substances to restore in the form of photons part of the energy absorbed during an excitement of a certain type (electric, chemical, mechanical, light energy,...). Fluorescence and phosphorescence are two different forms of luminescence: for fluorescence, the emission of photons is visible as long as the absorbed source of energy is active. For phosphorescence, the brilliance persists during a few seconds after the extinction of the source of energy, phenomenon which is called persistence.

Phosphor bands used for French stamps correspond to the above definition, ultraviolet light being used as source of energy of excitement, as shown by a note of the general management of the French Post authorities in 1973:

A phosphorescent pigment almost colourless in natural light with the peculiarity to emit a yellow-green light when it is lit by an ultraviolet light is incorporated to ink. Furthermore, after excitement by ultraviolet light has stopped, the product still emits for a few seconds this yellow-green light of luminescence.

These bands are overprinted in letterpress or in flexography.

According to J.J. Rabineau’s work (see reference 20), four types of phosphor bands, denoted A, B, C and D, were defined for the first issues of stamps with phosphor bands (other types of phosphor bands will appear after the disappearance of the Marianne de Béquet and will not be described here). The characterization of each type of phosphor bands can be found below (the images come from the site LES BARRES PHOSPHORESCENTES ET LEURS VARIETES):

Type A bands

  • Ink is viscous, thick and matt to the naked eye, hardly discernible in daylight ;
  • Bands, which seem homogeneous under UV light, are printed in letterpress (by means of a metallic printing plate covered with bronze) and naturally dried.
type A phosphor band seen under UV light on the left, magnified 60 times on the right

 

Type B bands

  • Ink is fluid (diluted with alcohol), matt, hardly discernible in daylight;
  • Bands have a peripheral tide line and are more or less hollow and very heterogeneous under UV light; they are printed in letterpress (by means of a metallic printing plate covered with plastic) and infrared dried.
type B phosphor band seen under UV light on the left, magnified 60 times on the right

 

Type C bands

  • Ink is viscous, thick and pasty in the naked eye, brilliant in glancing light;
  • Bands are rather heterogeneous under UV light, with a more or less broad peripheral tide line; they are printed in letterpress by means of a rubber or plastic printing plate and UV dried.
type C phosphor band seen under UV light on the left, magnified 60 times on the right

 

Type D bands

  • Ink is viscous, thick and slightly brilliant in the naked eye and in low-angled light, highly visible in daylight;
  • Bands have a soft peripheral tide line under UV light with a more or less pronounced dotted aspect; they are printed in letterpress by means of a metallic printing plate and infrared dried.
type D phosphor band seen under UV light on the left, magnified 60 times on the right

 

The stamp 0,50F Marianne de Béquet is 20 mm wide and 26 mm tall: the figurine is 17 mm wide and 22,5 mm tall, which leaves a margin of 1,5 mm on each side. Phosphor bands are 3 mm wide and 22 mm tall.