Section 5: Printing
How NER Stamps were printed
This is a very brief introduction. There is much more information in Section 5 of the Catalogue, plus many helpful illustrations.
The printing process is significant because it governs the nature of the variations which can occur. Most NER stamps were printed using lithographic techniques. Lithography is one of several significantly different printing techniques that have been used in stamp production.
The lithographic process would be the third phase of stamp production - the first phase being the design of the stamp image, and the second phase being the creation of a master image (or original copy) to the agreed design.
What is Lithography, and how does it work?
Lithography is the process of creating or copying an image (or text) onto a flat surface and then using this flat surface to transfer the image to a sheet of paper (or other target surface). The flat surface initially used was a limestone block - hence the term stone. This stone had to be smooth and finely polished.
Basic Lithography depends on certain properties of limestone:
- When an image is drawn on (or transferred to) the stone using a greasy / fatty ink, the image adheres strongly to the stone. The amount of ink so far transferred to the stone would not be sufficient to transfer a lot of stamp images from the stone to paper
- When the stone is wetted, water is absorbed only onto those parts of the stone which are not covered by the greasy / fatty ink (viz. the 'non-image' parts of the stone), causing these parts to repel further inking
- When further greasy / fatty ink (enough for transferring stamp images to paper) is applied to the stone, this ink adheres to the previously inked parts, but is repelled by the wetted parts
Basic Lithography - using stones (Designs 1, 2, 3)
Stamps of Designs 1, 2 and 3 were printed using basic lithographic techniques, which can be simplified (very much simplified!) as follows (but there are numerous variations for each design):
- Cut a single-stamp Master Image (in a copper sheet), the same size as the final stamp pattern, but without any value shown
- Ink this copper
- Lay a sheet of paper on the copper to create a transfer. The transfer sheet picks up ink from the copper
- Apply the transfer to a stone (a small limestone block). The ink now adheres to the stone
- Create a separate master image for the first value number and similarly transfer it to the same stone. This is now a Value Stone for this particular value
- Take multiple transfers (small stamp-sized pieces of paper) from this Value Stone and patch them together to create a full-sheet sized transfer page
- Apply this transfer page to a full-sheet sized limestone block, creating the Printing Stone. The ink from each image on the transfer sheet adheres to this Printing Stone
- Apply further ink to the Printing Stone. The ink adheres only to the already-inked stamp image areas
- Press a sheet of paper onto the Printing Stone to create a sheet of printed stamps
Repeat steps 2 - 9 for each value of this set to be printed.
Photo-Lithography - using Negatives and Plates (Designs 4, 5, 7-11)
Stamps of Designs 4, 5, 7-11 were printed using photo-lithographic techniques, probably using negatives in the Egg Albumen Process (still practiced in the 1950s and possibly later). These processes are simplified (very much simplified!) below.
- Assemble the Master Image as a drawing on paper (without a value). This is often a complex multi-stage photographic task
- Draw an original copy for the first value number, create a negative of it (number negative), and also positive mask of it (number mask)
- Photograph the Master Image to create a negative of the Master Image
- Expose a sheet of photographic paper using the negative of the Master Image (superimposed with the number mask)
- Before developing this sheet, expose it a second time using the number negative from step 2
- Now develop the sheet, and take a negative from it (on a glass slide). This is now the Value Negative
- Dissolve powdered egg albumen (the white of eggs) in water, and mix it with ammonium dichromate in a weak solution of ammonia
- Coat a full-size metal plate (usually zinc, or aluminium) with this egg albumen solution. Allow the coating to dry
- Insert Value Negative into the slot at the foot of a light box (explained more in the Catalogue)
- Place the light box over the first stamp position on the plate, and expose the negative. The light hardens the egg albumen coating through the transparent parts of the negative (viz. the lines of the image) but does not affect the 'non-image' parts of the coating which are covered by black areas of the negative
- In turn, move the light box to each subsequent stamp position on the coated metal plate and expose the negative (in the light box) again in each new position
- Wash off the un-hardened (un-exposed) egg albumen coating, leaving the 'non-image' areas of the plate with nothing on them. This is now the Printing Plate
- Ink the plate. The ink adheres to the hardened egg albumen, but not to the 'cleaned' parts of the plate (from which the un-hardened egg albumen coating has been washed off). At this point, you have a Printing Plate which functions in much the same way as the printing stones did for earlier issues
Repeat steps 2 - 13 for each value of this set to be printed.
There are again numerous variations for each design, and it is worth reading the descriptions in the Catalogue to get a better understanding of what is going on.
Letterpress - Design 6 only
There are no graphics on Design 6 stamps. These stamps were printed by letterpress, using movable type for the text, and metal strips for the lines.