Neutral Grey 43 ~ Some More Thoughts

Consider the wide difference between NG 43 and FS 16492 as shown in the schematic prepared for the recent blog on this subject. Both colours are made with the same pigments, but to different ratios. Now perhaps consider how NG 43 might shift more towards 16492 - although not as light - if the amount of titanium oxide (white) and/or yellow oxide (ochre) was increased in the mix, or the amount of carbon black decreased. Could such a degree of variance be tolerated in the production of the paint? Consider also patch painting by maintenance crews where there was a good chance that tins of NG 43, unless prepared very thoroughly, could demonstrate unequal dispersion through settling where the greater ratio pigment, white, might predominate. And finally consider chalking which produces a whiteish grey patina on the paint surface.

When it comes to the RAAF P-40N a useful little book that explores the subject of applied paint in forensic detail is John King's 'The Whole Nine Yards', celebrating and commemorating the life of A29-448 (42-104730) and her restoration. There is a whole chapter devoted to this subject, providing a valuable insight to Curtiss factory paint application and colours This follows convention in matching the undersurface NG 43 paint to FS 36173 based on extant samples from A29-448 and other P-40's. but the following comment is made:-

"There is little evidence in the literature of wide colour shifts in the Neutral Grey lower surface paint, other than normal oxidisation of the surface layers, which is easily removed with a mild abrasive."

Geoff Thomas, in an article for Airfix magazine in February 1983 ('True Colours'), matched NG 43 to Munsell 5 PB 4/1 - the closest FA value to which is 36118 @ 2.06 (where 2.0 or less equals a close match). But even so, 36118 is visually more blueish than the Munsell value as shown.  In his 'Eyes for the Phoenix' Geoff matched NG 43 to FS 36173, Methuen 22D-E2 and Munsell 6 PB 4.1/2.5. This variance probably represents matching to extant paint samples rather than a paint standard swatch. All these colours seem more typical for Sea Gray ANA 603 than NG 43.

The restorers of A29-448 were satisfied that the aircraft was in the Curtiss factory scheme and had not been repainted but the upper surface paint, assessed from extant samples from the airframe and from other P-40's where the paint surface had been protected from the environment (beneath flanges, fairings and panel joints, etc.) was darker and greener than might be expected. They matched it to FS 34083 rather than the more usually cited 34087 and commented that a can of US FS 24087 paint available to them was "browner  than any US colour seen on any of the P-40 paint samples available to the owners of A29-448". Of note is that FS 34083 is the closest FS value to the MAP paint colour standard swatch for RAF Dark Green at a very close 1.14.

For those who like to experiment with primary pigments in mixing colours the pigments for FS 34083 are titanium dioxide (white), natural raw umber, chrome yellow (red shade) and carbon black (blue shade). One formula for Olive Drab provided to MAP specifies chrome yellow (or molybdate orange), chromium oxide green, pure iron oxides (red or yellow), titanium oxide and carbon black. This formula has been matched to FS 34084 which is very dark indeed.

On some long exposed and weathered P-40N airframes with degraded paint examined in the 1960's at the Rukuhia dump, the colours showed "the well known colour reversal of the Olive Drab and Medium Green disruptive pattern on the plan-view and vertical surfaces: the OD had weathered to green and the Medium Green had weathered to a light brown." But interestingly not all the airframes showed this reversal and when weathered samples were cleaned with an oiled cloth the reversal disappeared and the colours reverted to shades closer to those expected. This suggests strongly the effects of chalking and the application of paints of exactly similar colour appearance originally but of different pigment constituents, with those exhibiting more apparent colour shift probably containing a higher proportions of extender.  

Medium Green 42 was supposedly used to obliterate the original US markings on some RAAF P-40N's, resulting in discs of an apparent lighter colour visible behind the RAAF roundel and codes in some photographs. One has to be careful here because the tonal differences seen in photos do not always coincide neatly with the colour differences of the actual paint. Medium Green 42 is another colour for which there are various equivalents cited, including FS 34092 which seems rather desaturated or faded. FS 34092 is also sometimes cited as a match for RAAF Foliage Green but extant samples of that paint are much darker and more olive. Foliage Green would seem a more likely paint colour for the over-painted markings but the tonal differences to the OD are almost in reverse to what is seen in the photos. Some references maintain that Medium Green 42 and Foliage Green were identical colours. The applied paint might have ended up appearing very similar but the Medium Green standard is not the same as extant samples of Foliage Green examined.

Geoffrey Pentland* suggests that Foliage Green was used to touch up the OD paint on the RAAF P-40N's, including Atherton's 'Cleopatra III'. He also reports that some P-40 undersurfaces (e.g. in 86 Sqn) were re-painted Sky Blue but as mentioned elsewhere the supposedly unpainted ailerons appear much lighter in photos than the darker undersurfaces, rather than the other way around. Most P-40N's seemed to have retained the NG 43 undersurfaces and it seems more likely that the ailerons, subject to maintenance, replacement and re-covering, were re-painted Sky Blue or a lighter grey like Medium Sea Grey which Pentland describes as fading "quickly to a near-white colour which then required repainting". Many of the aircraft were kept polished which deepened and intensified the colours.

Interior colours are covered in 'The Whole Nine Yards' too, with the author citing the formula from the Preliminary Handbook of Erection and Maintenance Instructions for the P-40N:-

Zinc Chromate Primer (AN-TT-P-656) 100 Gallons
Titanium Oxide (AN-TT-P-436) 1.3 lbs
Lampblack (TT-L-71) 0.1 - 0.4 lbs
or Carbon Black (AN-TT-C-121) 0.1 - 0.4 lbs
Magnesium Silicate (Commercial) 8-10 lbs

The points to note here are the variable amount of black in the mix and the addition of white (especially for those who assert that Interior Green was a mix of only Zinc Chromate Primer and Black). The author points out that the curiously confusing layout of this section could have resulted in both Lampblack and Carbon Black being added to the mix, as well as the variable proportions which would affect the final colour appearance. Some hobby paint interior greens are quite garish and "leap out" on models, perhaps the result of formulating colour based on flash photographic images of cockpits, but it is an illuminating exercise to mix the colour using the specified constituent pigments, including real Zinc Chromate rather than "yellow". The variance in black might have been specified to compensate for a yellow-green variance in AN-TT-P-656 in order to better match the standardisation for Interior Green (ANA 611) as ANA Bulletin 157 on 28 Sept. 1943 had stated:-

"ANA 611 Interior Green is intended for standardisation of the product obtained by tinting zinc chromate primer, Specification AN--TT--P--656, for shop coat or interior finish purposes." 


The Dictionary of Aircraft Maintenance Terms, Section H Paint and Dope (T.O. No. 30-1-2-H) published by HQ ATSC in November 1944 defines 'Primer, Zinc Chromate' as follows:-

"A semi-transparent, greenish-yellow liquid of zinc chromate base, thinned with toluol, very generally used as a primer on aircraft metal surfaces. Because it dries quickly, coats of lacquer, enamel, etc., can be applied on top it within a few minutes, though it is best to allow the primer to set for a few hours." 

(Toluol or Toluene was an industrial grade solvent widely used in lacquers, paints and synthetic enamels.)

* RAAF Camouflage & Markings 1939-45 Vols 1 & 2 (Kookaburra Technical Publications Pty Ltd., 1980)
  

Neutral Gray 43 ~ The Clue is in the Name

Something of a departure from regular fare - again - as a discussion at Britmodeller about the best hobby paint to represent the USAAC paint colour Neutral Gray 43 (NG43) triggered some thoughts on the matter. Regular readers will know that one of the motivations behind this blog is an attempt to separate colour facts from colour fictions - or perhaps more correctly from colour 'myths'.  Not necessarily in any kind of revisionist or heretical way, although that often seems to be the result, but by examining what is actually known, as dispassionately and objectively as is possible and applying established colour science to it. This is more often than not contrary to perpetuating what is thought to be known and which, when investigated, is sometimes found to be based on unreliable or even obscure foundations. 

The first reality check with NG43 is the idea it that it was a "pure" neutral grey consisting only of black and white pigments. It wasn't. The pigments specified for NG43 in 14105 (camouflage pigmented nitrate lacquer) and 14106 (camouflage pigmented nitrate dope) were titanium dioxide, yellow iron oxide and lamp black. More on these pigments later.

The second reality check is that there is only one colour value in FS 595B that approximately matches these pigments (see below) and none that match the colour. And this is further borne out by conducting colour comparisons to crunch the numbers. There is not a single FS value that comes even close to the 2.0 or less requirement of the DE2000 difference calculation criteria.  The FS values most often cited for NG43, FS 36270 (supposedly in error) and 36173 (supposedly correct)  both contain rutile titanium dioxide (white), phthalocyanine blue (red shade) and carbon black (blue shade). In addition 36270 contains benzimidazolone yellow whilst 36173 contains red iron oxide (blue shade). This is not surprising as contrary to what is often asserted NG43 did not evolve into any other standard colour after its appearance in Bulletin 41 of Sep 16 1940. It was replaced by the ANA paint colour Sea Gray 603 introduced in ANA 157 on Sep 28 1943 and that evolved to become FS 36118.  

The closest FS value to NG43 is FS 36152 @ 3.54. However, it is still more blueish in appearance and the constituent pigments are rutile titanium dioxide, phthalocyanine green (blue shade), chrome yellow (red shade) and carbon black (blue shade). Chrome yellow is a stronger, brighter and clearer yellow pigment than yellow oxide. The closest FS value to NG43 in pigment content terms is FS 16492 which contains almost exactly similar pigments of rutile titanium dioxide, yellow iron oxide and carbon black but it is clearly much lighter than NG43 as a result of ratio differences.

I do not know where the idea of a blueish NG43 comes from, but there is a prevalent tendency for "greys" to be perceived as blueish and many of the NG43 hobby paints seem to show this trait. Even though many modellers repeat the popular idea that NG43 was a pure mix of black and white they seem comfortable with accepting these blueish grey hobby paints as representative and in citing FS 36173 as a match!  Perhaps this operates on the "decorator principle"? I also get the impression that a lot of these matches are being made under artificial hobby room tungsten light which draws 36173 closer to a warmer, neutral grey. Certainly the swatch included in J F Dial's 1964 'United States Camouflage WW II' (Scale Reproductions) is significantly more blueish in chroma than the paint chip and printed chip in both the Archer books*. Again I emphasise that the discussion here concerns the paint colour standard and does not necessarily mean that all applied paints matched that standard perfectly and/or did not exhibit colour shift as a result of manufacturing processes or environmental and age related stresses. Please, no more colour photographs to "prove" points about paint!

Another clue to the real characteristics of the colour is the fact that for the first time in Spec 14057-C of 27 Dec 1939 Munsell colour notations had been cited for the colours and Neutral Gray 32 was notated as Munsell N5 (in the 1929 system). Neutral Gray 32, an earlier temporary camouflage paint, was identical to the subsequent NG43. The 1929 Munsell N5 is entirely consistent with the Archer chips.

Both Testors (#1725) and Xtracolor (X133) versions of Neutral Gray are said to be matched to FS 36270 and 16270 respectively, but the Testors paint is actually manufactured only with titanium dioxide (15-20%) and carbon black (0.1-1.0%), although it contains hydrous aluminium silicate (an extender also known as China clay) and magnesium silicate (a filler also known as 'talc'). I haven't tested the Testors but I presume it to be a genuine neutral gray in colour? The Xtracolor paint appears as a very close match to FS 26270 but is a little lighter and warmer. White Ensign Models (WEM) Colourcoats ACUS13 WW2 USAAF Neutral Gray has the hybrid designation "ANA 43' (NG43 was never a ANA paint colour). It is a tad darker and slightly more blue-green in hue than FS 36173.

Titanium dioxide (C.I. pigment white 6) was developed in the 1920's and was in wide scale use as a white pigment by the 1950's. Prior to its use white pigments used in paints were compounds such as lead carbonate, zinc oxide, antimony oxide, lead silicate, lead sulfate and co-precipitated forms of these compounds. Other than zinc oxide most of these other forms of white pigment have become obsolete, not least because of issues of toxicity. It is manufactured in two processes, by sulfate and by chloride from ores such as ilmenite or rutile. In the sulfate process the ilmenite ore is reacted with sulfuric acid to produce titanyl sulfate, which is then hydrolised to produce hydrated titanium dioxide. This in turn is then calcinated to produce titanium dioxide pigment. There are two main forms - rutile, with resistance to chalking - and anatase, with a tendency to chalk significantly.

As a digression, another reality check for modellers is the prevalent idea that only the sun degrades paint and then only to "fade" it. In the exposure environment the chemical and physical processes affecting a paint surface are complex, combined and cumulative as it is subjected to diverse and variable environmental stresses. The most significant are heat, oxygen, sunlight, water (both in liquid and vapour form), mechanical and thermal stresses, atmospheric pollutants and various chemicals which might be applied to it, usually deliberately to clean it or unintentionally from materials or solvents associated with other servicing or maintenance activity. The paint film also contains decreasing levels of residual solvent or water, or both, retained after application, as well as pigments, fillers, additives or trace metal impurities incorporated during manufacture - all of which will probably have some photochemical activity. The physical effects that can be expected include gloss loss, colour change, dirt retention, chalking, cracking, delamination, blistering, fouling and corrosion. 

The typical effects of chalking result in a whiteish-grey powdery patina across the surface which is not that obvious to the eye unless you rub your hand over it. Titanium dioxide is both a UV-activated oxidation catalyst and a UV absorber, with a tendency to absorb light at the blue end of the spectrum and to appear as a yellow toned white. As an oxidation catalyst free radicals are formed on the surface and oxidise the binder by photocatalytic degradation. This reduces any gloss and produces a friable layer on the surface of the paint film. The process will be exacerbated under direct UV exposure but even surfaces out of direct light will not be immune, for example a combination of extremes of heat and humidity will cause a similar degradation. Any paint that contains a majority of the anatase form titanium dioxide (such as greys and light blues) would tend to exhibit more chalking, which is why Ocean Grey, say, can appear to "fade" much lighter than adjoining Dark Green. A common fallacy of modellers is to assume that all camouflage paint colours "fade" or degrade at the same rate.

The effect of chalking on a grey paint would be to make it appear lighter (and with other colours lighter and more greyish) but typically the surface would be variegated rather than even in appearance, especially where it has been subjected to different degrees of exposure. How much lighter the grey becomes depends on the duration of exposure and degree of degradation, reaching a point where it could be almost off-white in appearance and ultimately where the paint breaks down through the whole film and begins to reveal the primer. Regular maintenance treatment will reduce the chalking process or delay it but not eradicate it entirely.

Now, to return to NG43, what should make us think that the form of titanium dioxide used in the paint was anatase?  Well, the same specifications make a point of requiring the "anti-chalking" variety of titanium dioxide for the Insignia White and Insignia Blue paints, a requirement omitted for NG43, which strongly suggests (and no more than that) that NG43 could be manufactured using the anatase form of the pigment.

Yellow oxide - or yellow iron oxide - exists in synthetic (CI pigment yellow 42) and natural forms (CI pigment yellow 43) It is produced synthetically by hydrating ferric oxide to a range of dull reddish-yellow to yellowish-orange brown hues, the final colour determined by the size of the particles in turn controlled by rate and duration of oxidisation and the concentration and pH of solutions. Yellow iron oxide is not therefore an identifiable colour by name alone. It is a relatively cheap pigment used extensively to produce cream tints with titanium dioxide. In common with red oxides it provides good light fastness (colour retention) and heat resistance, absorbing UV radiation to an extent which gives good durability. It has good opacity and good chemical resistance. It has poor tinting strength which means that when added to, say, titanium dioxide, a lot goes a very little way and the shades produced by it are usually dull rather than bright.  Why was it added to NG43?  Possibly to counter the chalking tendency of the titanium dioxide or to counter a blueing tint from the use of blue shade carbon black. The effect of a titanium dioxide and yellow oxide combination would certainly produce a warm tint grey rather than a cool blue-grey. 

Lamp black (CI pigment black 7), not to be confused with carbon black (pigment black 6) although related and sharing the same CI # 77266, is commonly used by the paint industry to produce a superior black colour. Carbon Black is much better in colour and tinctorial value than Lamp Black but the difference between their structures is not completely understood. Carbon blacks are often known by the name of the hydrocarbon they are made from, e.g. Acetylene Black or Benzol Black. It is usually made by heating oil, gas or acetylene at very high temperatures with limited air.   It has a very small particle size which can cause dispersion problems leading to poor gloss and poor colour. It can also have stability issues in air drying media and when combined with other pigments such as titanium dioxide it can flocculate, changing colour in storage. In pigment form, far from being constant, the hue varies from deep brownish or bluish or greyish to deep black.

* The Official Monogram US Army Air Service & Air Corps Aicraft Color Guide, Vol.1 by Robert D Archer (Monogram Aviaton Publications, 1995) and USAAF Aircraft Markings and Camouflage 1941-1947 by Robert  D and Victor G Archer (Schiffer Publishing 1997).

Seasons Greetings

Chris Huhne models his Department's answer to rising winter fuel costs. The pensioner's own breath is re-circulated to warm the lining of the Lib Dem Xmas Utility Suit.

Wishing all friends of American Aircraft for the RAF a Very Merry Christmas and a Happy New Year

Image credit: Secretary of State for Energy and Climate Change

That Old Chestnut - The Can of Worms

Modellers often describe colour related issues as a "Can of Worms", usually as a preliminary to drawing their own particular conclusion in one of those published celebrity builds which are avidly followed and where, by dint of modelling expertise, the sometimes contrarian choice of paint colours is often taken as some form of definitive guide. This is not always appropriate. In colour terms the plaudit "That looks good" is not always synonymous with "That is accurate" or even "That is close enough".

"Can of Worms" is usually taken to mean "a source of unforeseen and troublesome complexity". What it doesn't really mean is "different opinions in the absence of hard data". That is just speculation and/or disagreement. The arguments and counter-arguments involved might be based on hypotheses which might include  elements of complexity - or not. What it certainly doesn't mean is an absence of data per se. But because we live in an online world where it is much easier to present an opinion as a hypothesis, or to promote a hypothesis via an opinion, the distinction between complexity and the simple unknown is sometimes blurred. As a consequence the vacuum of the unknown is all too often filled with unverifiable assertions and counter assertions. Over time these become confusing to anyone trying to ascertain the base data - or lack of it. It is the speculation that often becomes the can of worms, not the base data or absence of data which for an objective mindset usually remain unchanged.

A case in point is the Brewster Buffalo. As built for the RAF we can presume with some confidence that it was painted in colours intended to represent the RAF Temperate Land Scheme (TLS) of Dark Green, Dark Earth and Duck Egg Blue (Sky). Nothing complex or "can of worms" about that. What we don't know is exactly what those paint colours were like or how far they differed from the MAP Standard colours. AFAIK there are no accessible extant paint samples, no colour photographs, no factory paint specifications and no paint company swatches (at least not Fuller). There are contemporaneous descriptions, subjective as well as subject to interpretation, and there may be contemporaneous colour paintings. Speculation about the probabilities and possibilities around these unknowns is not a can of worms - it is just speculation.

Some modellers understandably approach builds where there is an absence of solid colour data with trepidation and there is these days a more evident need for reassurance - or consensus - about the colours to be chosen. Whether this arises from some harsh judgements or snide comments at model shows I couldn't say but the notorious "colour police" waiting to pounce on the wrong RLM seem, at least online, to be an urban myth. Sure there is debate and disagreement, often heated, over colours, but very rarely is a model displayed online criticised harshly for its paint choices - even when it deserves it. Nevertheless "can of worms" often appears as a plaintive, to discourage a mythic storm of criticism (it seldom discourages a storm of heated discussion). But ask yourself, next time you comment on model colour, whether approval or disapproval rests on the "decorator principle" ("I like the pretty colour you have painted your model. I'm going to do the same") or the "accuracy principle" ("I think the colour looks correct, based on the verifiable data available"). Nothing really wrong with either, except when they pretend to be each other. 

In modelling the expression "can of worms" is not just misused, it is over used. It is a cliché. And it is all too often, sadly, a cloaking device for ignorance. So choose colours and paint your Buffalo with confidence, in the freedom and joy of objective interpretation - not in the angst of seeking a consensus of speculation. Just my two cents worth . . . . .

Dupont, FS and MAP colours

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. 

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.

Brewster Buffalo Colours

The current thread on Brewster Buffalo colours at Britmodeller gives me pause for thought. In January this year I wrote in another thread at Britmodeller:-

"I do have reliable measured colour values for the Du Pont upper surface browns and green from the original swatches but have not prepared or published rendered chips and comparisons yet. When I started comparing the colour values that had been given for these hues in the past (FS, Pantone, Methuen, etc.) I found disparities between them that were impossible to reconcile - probably the results of attempts to match subjectively and visually under different forms of illumination and perhaps from colour photos. The paints are very much deeper and more strongly saturated than MAP colours and the dark green has a different character entirely to MAP Dark Green, being more of a forest green in appearance than an olive green. One thing I can confirm and that is that the dark green is not like 34092 at all - the difference calculation to that is over 15 where less than 2.0 = a close match but I guess "scale colour" may come into this. The full scale paint does look very dark indeed but colour photographs reveal how it faded under uv exposure. I have nothing on the Fuller paints yet."

Since then I have published rendered chips of the Du Pont TLS colours here in August together with a comparison to the MAP colours they equate to. The closest FS match to the green is 14056 and for the darker of the two browns 26120. The lighter brown is close to 30140. The difference calculations are 0.87, 2.73 and 0.75 where < 2.0 = a close match so they are all useful comparisons, although the darker brown is a little lighter and not so chocolate in appearance as 26120. FS 34092, often cited for  Dupont 71-013 is the same basic hue (Munsell 4.7 G 3.5/1.9 vs 1.5 G 2.0/1.7 but is significantly lighter and de-saturated than the actual paint colour, as though representing a very faded version. It's a personal choice but on a 1/72nd scale model I would probably select a tone somewhat between 14056 and 34092, moving more towards 14056 for models in larger scales. Even allowing for "scale colour" the dark green needs to look like a "dark green" rather than a "bright green" on a model!

The mention of Fuller paints is pertinent because I now have good reason to believe that Brewster procured Fuller paints for their export aircraft and those used on the Buffalo might have been the same as those applied to the Douglas Boston:- Fuller enamel TL-8713 Brown, Fuller enamel TL-8714 Green and Fuller enamel TL-8715 Blue (Duck Egg). Unfortunately I have not yet been able to find any charts, swatches or chips for these paints and the only clues as to their appearance are the Getty Images colour photographs of Bostons that I posted on the blog in June 2010.

Reading the current thread at Britmodeller drives home to me just how absolutely pointless it is posting this sort of data. 

Airfix Curtiss Hawk 81-A-2

There is a big spread on Airfix's new 1/72nd Curtiss Hawk 81-A-2 in Issue 12 (November 2011) of the Airfix Modelworld magazine. The kit offers only a single markings option for an aircraft of the famous Flying Tigers (American Volunteer Group or AVG). A previous post here revealed that the under surface colour suggested in the Airfix kit is Humbrol Matt 28 Camouflage Grey. This has now been confirmed by examination of this excellent kit. The magazine goes further in providing a splendid multi-view profile of the subject aircraft calling out the Humbrol and FS 595B colours - 116 Matt US Dark Green (No FS), 117 Matt US Light Earth (FS 30219) and 28 Matt Camouflage Grey (FS 36622). These are all called out as approximate equivalents to the correct Du Pont paint designations 71-013, 71-009 and 71-021. Unfortunately they are not. The Du Pont paints were darker and had a higher chromatic intensity (being more saturated) than the MAP paint colours and there is some doubt whether 71-009 or 71-035 (or both) were applied to the AVG Tomahawks. The closest FS match to the very dark Du Pont green is 14056 which is nothing like Humbrol's 116 even allowing for oxidising, chalking and fading of the paint surface. However, the box artist Adam Tooby has done a good job of representing the colours in his dramatic image.

A build article is included in the magazine where the author Tony O'Toole uses Humbrol equivalents for RAF Dark Earth, Dark Green and Sky to represent the colours on the AVG aircraft. This is arguably a more representative choice than the colours suggested by Airfix and, dare I say it, makes his superb model "look right". He refers to Sky as a "worthy alternative" for the under surface colour. 

The plot thickens just a little. Humbrol 28 is reported to be a match for FS 36622 whereas there is no match in the Humbrol range for the FS equivalent of Du Pont's 71-021 Sky Type S Grey which is 35622. The colour value 36622 arose in a discussion at Hyperscale and was reported here but I still don't know whether this was in error for 35622 (a typo) or based on an interpretation of colour photography or on something else. Having said that it might not be such a bad choice to represent  the heavily oxidised and chalked appearance of the paint colour on an AVG model. It is certainly a preferable choice to US Aircraft Grey/ANA 512/FS 36473/Tamiya Sky Gray but ironically, it is the suggested upper surface colours that are probably more contentious!