Hello all, my humble opinion is that what you have noticed here is not
at all a 'printing' oddity but a pure and simple cartographer's error.
Text intended for printing in a particular colour would have been
placed on the relevant 'overlay' ; a sheet of draughting film used to
hold linework, text strings, or symbols that were needed to be kept
separate for whatever reason. The cartographer simply made an error
and placed the text to the wrong piece of plastic; this error was not
spotted during the examination stage. Today's computer-based methods,
conceptually use the same approach where blue names are placed on a
blue 'layer', and the human operator is still free to make the same error.

Traditionally the OS had a whole chain of checking and examination
stages which enabled almost all errors, of any kind, to be spotted.
But no map is perfect... it just can't be done. So it is inevitable
that artifacts of this kind are seen from time to time. And I
believe, in spite of computer-based map compliation systems, that the
number of such errors may continue to grow.

Over the years, checking procedures have become less and less
rigorous, due to time and cost constraints and a misplaced belief in
the effectiveness of a 'get it right first time ' approach. I stress
that this is my opinion and interpretation of how the aproach to map
examination changed over time. 30+ or so years ago, the OS philosphy
was to put absolute quality first; controling expenditure was not a
major driver then. But the realities of 'commercial' needs means that
quality will be compromised from time to time, and in many ways.

Comments anyone?



intended for --- In ordnancemaps@..., "Leslie V Watson"
<Lez4Lynne@A...> wrote:
>
> In reply to Alan Bowring:
>
> I can't add anything on how OS maps are printed, but on looking at
> my copies of Sheet 160 I see that near to `Nant y
> Rhaeadr', `Waterfall' at SN 753436 changes from blue to black on
> edition A3. While `Nant y Rhaeadr' reverts to being all blue type on
> edition B (2000), `Waterfall' remains in black, and is still black
> on edition B1/. As a water feature it should be blue, like the other
> identified waterfalls nearby at SN 730417 and 754429.
>
> This area around Mynydd Mallaen is on the overlap between sheets
> 146, 147 and 160. On 146 and 147, `Nant y Rhaeadr' is always in
> blue, but `Waterfall' at SN 753436 changes to black on sheet 146
> edition B (2000) and 147 edition C (2001). This is probably due to
> the adoption of a single database from which to produce 1:50,000
> Select Maps. Perhaps the detail on sheet 160 was preferred, thereby
> inadvertently extending the use of erroneous black type for
> this `Waterfall' to all 3 sheets.
>
> Returning to the 2 colour `Nant y Rhaeadr', there is a similar
> oddity on sheet 18 edition B1/ (2003). Here at NF 874648 is `Loch
> Tarruinn an Eithir' (2 lines of text). `Loch Ta…' and `an Ei…' are
> in blue, while `…rruinn' and `…thir' are in black.
>
> Bill Henwood
> 27/07/2006
>