Tuesday 9 August 2022

Unusual printing flaw on 2nd class Datamatrix definitive reported.

My thanks to Andrew P for sending a fine picture of an unusual flaw on a new datamatrix definitive.

Here are Andrew's pictures:

 Doctor blade flaw on barcode of 1st class purple datamatrix stamp from a book of 8 (rotated 90º)

1st class purple datamatrix stamp from a book of 8 with doctor blade flaw on barcode

This is a Doctor Blade Flaw - 

DOCTOR BLADE: A printer blade which removes surplus ink from printing cylinders. Stamps affected by faults in this process are often referred to as Doctor Blade errors or flaws.  They are not consant and therefore not catalogued.

As I reported when the first such stamp was issued, the 2nd class blue business sheet, the stamps are, as usual printed in a single colour.  But the datamatrix code was printed in a combination of colours -- need to get the microscope on the new ones to find out if this has continued.

2400 dpi scan revealing magenta dots misaligned so that some are above the edge of the cyan.

400x magnification showing uneven 'splash' of magenta at random (which shows as darker blue), and more rounded and sharp black dots, possibly regularly spaced (further investigation needed on these).

I've seen them before on booklet covers and stamps, but this example demonstrates clearly that the magenta ink-spread is due to the colour used in the datamatrix code.

Has anybody else seen anything like this recently?


  1. Hi, I have many Dr blade flaws on these stamps already, (affecting the stamps themselves as well as the matrix). I am not adept at adjusting the dpi or magnification of them but can send scans with labelling of the flaws if you would like them.

    1. Thank you that might be useful.
      If you are scanning, then using the 'non-simple' mode (the name varies according to brand) should be straightforward. If you use a phone, then the best modern ones produce very sharp pictures. Send a couple of what you have to my email address and I'll see how usable they are.


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