15h – cracked printing plate at 11/II
Updated 24 June 2017
Plate cracks occur on several values of this issue, especially at marginal stamp fields where the risk of mechanical damage is naturally higher. While reconstructing the first and second plates of the 15h (POFIS no. 7) I came across a very interesting example of a cracked printing plate.
A pronounced crack of the upper-left corner occurs at field 11 of plate II. I believe it arose from damage to the plate during routine cleaning. Stamps with this damage are, in my view, scarce.
How the crack may have arisen
Cleaning the plate stresses the exposed edges and corners of a field the most, which is where a hairline crack most easily starts. On the next impressions ink gets into it — printing as an extra line — and the pressure of the press widens it a little further with every pass. That is why the crack grows over time, as the phases below show.
Development of the crack
The crack developed gradually, as the images of the individual phases show:
Phase 0 – intact plate · Phase 1 – faint deformation · Phase 2 – the plate shows a crack · Phase 3 – the crack grows · Phase 4 – final phase
| Perforation | Phase 0 intact plate | Phase 1 plate not yet cracked, but shows deformation | Phase 2 plate shows the crack | Phase 3 the crack grows | Phase 4 final phase of the crack |
|---|---|---|---|---|---|
| imperforate | ✓ | ✓ | ✓ | ✓ | |
| A | ✓ | ✓ | ✓ | ||
| B | ✓ | ||||
| C | ✓ | ✓ | |||
| D | ✓ | ✓ | ✓ | ||
| E | ✓ | ✓ | |||
| F | ✓ | ✓ | ✓ |
Addendum: an interesting article on this subject by Jaroslav Michalík was published on infofila.cz: infofila.cz – Hradčany: cracked printing plates.