The question of FS 25622 matching Dupont 71-021 came up in an offline conversation as a colour comparison site has suggested it as a match for MAP Sky Blue (together with FS 25550). The schematic above shows the colours.
FS 25550 is the closest FS colour to MAP Sky Blue but it is not a particularly close match @ 5.51 where less than 2 = a close match. It is lighter and brighter. FS 25622 is close enough to the Munsell value of 71-021 to be considered a useful match but the original colour has a slightly stronger chroma.
These variances are probably not worth worrying over in modelling terms because in addition to the expected variables in manufacturing processes most of the under surface light blues and light blue-greens contained anatase Titanium Dioxide (white) as their main pigment, together with China clay extender. Both these ingredients cause severe chalking of the paint surface which after a few months of exposure and depending on the environment and maintenance regime will make the colour appear significantly lighter and more greyish-white. Having said that there is still a need to represent the colour in an identifiable way so 25622 would not be the best FS colour to represent MAP Sky Blue.
Seen in isolation it is easy to perceive 25622 as a cool "light blue" but the colour actually has a green aspect and is a pale blue-green. MAP Sky Blue is a cool, sightly greyish light blue, not as strong chromatically as many seem to think. The Sky/Duck Egg Blue formula was too subtle and too imprecise for the paint technology of the time to produce consistent results so variance was inevitable. Also, whilst paint manufacturers were given swatches to match against and the preferred pigment formula "solution" was suggested it was not mandatory. Manufacturers were free to select their own pigment formulae provided the applied paint matched the swatch. What happened afterwards was unpredictable as pigments, whilst creating the same or similar enough colours using different formulae, age and degrade in different ways. Even in the modern FS 595B standard the procurement process allows for the "Visual Evaluation of Color Differences of Opaque Materials" (ASTM D 1729) on the basis of whether a critical or general match is required. This subjective, visual evaluation allowed for an inspector to decide what was "close enough" so incremental variances between pale blue-greens towards more green or more blue could be expected to pass through the process. But the inspectors were not stupid and neither were the staff of the handling and receiving units so it would be wrong to suggest that "close enough" could include paints formulated to completely different hues, such as neutral greys. Establishments in Britain testing specific aircraft types from manufacture were expected to report on all aspects, including whether camouflage paint was "acceptable" in both colour and quality of application.
Another thing to bear in mind is that many contemporaneous observers not versed in the official paint names would probably see and describe these colours simply as "green" and "brown", the under surface colour being "light blue", "duck egg blue" or "sky blue" all interchangeably. The subtle nuances of these paint colours are often important only in hindsight and from a modelling perspective.
Another thing to bear in mind is that many contemporaneous observers not versed in the official paint names would probably see and describe these colours simply as "green" and "brown", the under surface colour being "light blue", "duck egg blue" or "sky blue" all interchangeably. The subtle nuances of these paint colours are often important only in hindsight and from a modelling perspective.
The tendency for paints of the time to chalk badly was well known and although I have no specific evidence for it I suspect that the more deeply saturated paint colours applied in US manufacture recognised this and were intended to compensate for it, especially where procurement was under commercial contract.
Receiving units in Britain included "sister" firms charged with providing maintenance and manufacturing support for specific US aircraft manufacturers and aircraft types. This support extended to thorough documentation concerning the paint colours applied to aircraft, even to itemising their pigment compositions, in order to assist in the procurement of matching paints in the UK. The whole process, whilst acknowledging the realities of aircraft and paint production, was by no means as cavalier or as casual as some modellers believe and would have us believe. In the case of the Douglas Bostons the strong blueishness of their under surface colours was the subject of both comment and complaint at the time. So far I have not encountered a single reference to paint colours expected to be supplied as "duck egg blue" actually being grey.
0 comments:
Post a Comment