Japanese Anti-Submarine Aircraft in the Pacific War ~ A Review

Japanese Anti-Submarine Aircraft in the Pacific War by Ryusuke Ishiguro and Tadeusz Januszewski, published by MMP Books, has been long and eagerly awaited since first announcement here in February 2017 and subsequent updates. This magisterial book does not disappoint and is an important addition to the accessible English language literature of WW2 Japanese aviation as well as an important subject in its own right. Far from being an arcane or obscure aspect of Japanese aviation the airborne anti-submarine response was a critical component of both Navy and Army airpower during the Pacific War, deployed against an increasingly effective, wide ranging and destructive Allied submarine campaign. The latter has been covered in the West to great depth in various books over the years but most of them have paid only superficial attention to Japanese anti-submarine warfare (ASW), either focussing on surface vessels or making scant reference to Japanese ASW aircraft, and usually in generic terms. Books on the development of Air to Surface radar follow a similar pattern, where the Japanese programme and projects are covered all too briefly, if at all, to no great depth and leaving many unanswered questions.

Here then is a book that sets out to answer those questions and delivers, often for the first time in the English language. But more than that it provides a seminal reference to the subject from the tactical to the technical, and should therefore leave no excuses for future naval historians of the Allied submarine campaign to omit its impact or reference to it. In that sense it is not just an 'aviation' book but is of undoubted naval interest as well. For modellers it should be required reading for any contemplating a collection of Japanese aircraft models in ASW guise - and there are plenty to choose from here! But, because many aircraft were adapted to the ASW role by both the Navy and Army the book is of more general interest too. Each type, whether adapted or specialist, operational or experimental, receives the same degree of attention, with full background, development history and operational use where appropriate, together with newly drawn and excellent plans. This coverage of some familiar types already described elsewhere might be questioned by some but this reviewer thinks the approach is correct. It results in a consistent structure to the book with all relevant information in one place, achieving a balanced presentation. Wiki entries on individual Japanese aircraft are patchy and too often full of errors. The standard English language reference work for Japanese aircraft in the Pacific War is the Putnams book, by R J Francillon, with the latest edition now being 18 years old. It won't be accessible to everyone and second hand copies are not cheap. Otherwise one must look to monographs on individual aircraft types with many gaps still to be filled. Too easy therefore to get drawn into reviewing a book from the perception of an interested and informed 'pundit' with an already extensive subject library, who might think that 'there is nothing new here' for those types, rather than to consider those taking up an interest for the first time and new to the subject. But in fact there is much that is new throughout this book and the authors have worked long and hard to unearth it. The whole package is excellent.    

The book consists of 248 pages and is divided into sections with the first 11 pages covering patrol service, IJN units and tactics and sea escort service. There follows a detailed compendium of individual ASW aircraft, first Navy and then Army, examining their development and operational use, with performance data tables and, in some cases but not all, a discussion of their colour schemes with some interesting information and insights. These sections prompt the obvious gaps for kits, especially of Army types. New mainstream 1/72 kits for the Kyushu K11W Shiragiku, Kokusai Ki-76 and Tachikawa Ki-54 would be welcome! After the individual aircraft sections there is a chapter on patrol and anti-submarine aircraft equipment, followed by one on anti-submarine bombs and torpedoes, and finally an exposition of IJA aircraft carriers. Although individual these chapters link to present a holistic whole and a book which delivers a satisfying, well-structured read as well as a useful reference work to dip into as required. Of particular note is the inclusion of operational aircraft types which have received little detailed coverage elsewhere - the IJN's Kyushu Q1W Tokai, the IJA's Kayaba Ka-Go and Ki-76 Stella. That alone gladdens the heart but some of the even more obscure proposed and experimental types are described as well. The coverage is comprehensive.  

There are 22 sets of aircraft plans, to 1/72 scale where feasible, 229 photographs, four in colour, and numerous diagrams and tables, as well as excellent colour cutaways by Giuseppe Picarella. Those detail the Q1W1 Marker Bomb Rotary Launcher, Q1W1 cockpit layouts and radar equipped B5N2 cockpit layouts. The photographs, albeit on matt paper, are clearly printed and presented to good sizes, the majority being absolutely relevant to the subject matter; in fact a remarkable compilation of many new and interesting images as well as some more familiar ones shown clearly for the first time. Collected at the rear of the book are 38 large colour profiles by Dariusz Karnas representing the aircraft types described in the text, with nine additional plan or detail views in colour. The profiles do not have individual captions which seems a pity, so that some controversial schemes like the blue Ki-51 of Dokuritsu Hiko Dai 49 Chutai (page 245), for example, have no further description or elaboration.  There are some minor typos in the book and some inconsistencies in terminology but those pale against the wealth of information provided and its attractive presentation. A video preview of the book from publishers MMP is available here and it is very highly recommended.

 

With thanks to Ryusuke Ishiguro and the publishers for the review copy. 

Image credit: © 2018 MMP Books

An Early Vietnamese Military Aviation Pioneer

One of the first military aviation pioneers, a street in Casablanca named after him, was a Vietnamese, Lieutenant Do-Huu Vi, a French Foreign Legion officer serving in the French Army's 1st Aeronautical Group which was sent to Casablanca in February 1912 with four Blériot monoplanes. Their sponsor was  General Lyautey, later Resident-General of Morocco, influenced perhaps by his mentor General Joseph Galliéni who had confounded his contemporaries in the 1911 manouevres in France by using aerial reconnaissance to capture a Colonel of the Supreme War Council and all his staff.

The Moroccan Aero Group spent five months on preparatory familiarisation flights, planning routes by stages and the siting of emergency landing grounds and fuel depots. On 17 August the first operational sortie was flown by Lt Do-Huu with Lt Van den Vaéro when they provided air reconnaissance for a column under Colonel Robillot south of Fes.  Do-Huu, without proper maps to navigate, drew sketch maps showing the position of hostile concentrations and dropped them to the column in weighted bags. Flight was challenging in the heat of the Moroccan summer as the Blériot's 80hp engine could not ascend above 4,600 feet, dust impeded fuel flow, damaging the engines and there was constant turbulence. to contend with. In May Lyautey had requested bombs but they were not available, however the number of Blériots was increased to six. Aerial bombing was not conducted in Morocco until April 1914 when 3 kg bombs were dropped in support of General Gouraud's campaign against the Tsouls tribe. The bombs were manufactured in Morocco with glazed earthenware casings. The tribesman responded with mass rifle fire, bringing down the aircraft of Capt Hervé and air mechanic Cpl Rocland on 8 April 1914. They were killed on the ground and their heads displayed around the Tsouls villages.

In December 1912 Lt Do-Huu flew a daring reconnaissance sortie in the Blériot to the fort at Dar el Kadi where Major Massoutier was under siege. In November 1912 a second section of the Group had been established at Oujda with five pilots and Deperdussin two seaters (below), flying operational sorties from January 1913.  

Lt Do-Huu was one of five sons of a prominent Vietnamese family in Saigon, his father the honorary mayor of Cholon. He was born on 2 February 1883, educated in France and in 1906 was commissioned à titre etranger at the military academy at St Cyr. He served in the 1st Regiment of the Foreign Legion in Morocco from 1907 to 1910 before undertaking flying training and gaining pilot's licence no.649 from the Aéro-Club de France and military licence no.78. Do-Huu remained in Morocco until 1913. After touring in France he returned to Saigon in 1914 to explore the use of the Lambert hydroplane (below) on the Mekong and Red Rivers. 

The outbreak of war saw Lt Do-Huu return to France where he continued operational flying, and all aircraft in Morocco were also returned to France. In 1915 a bad crash during bad weather left him with very serious injuries - a fractured skull and jaw, his left arm nearly torn off and in a coma for nine days. On partial recovery he insisted on returning to combat flying but his crippling injuries prevented him from piloting an aircraft so he became an observer in the 1st Bombardment Group, flying on sorties over Germany from Malzéville with Marc Bonnier as his pilot. Eventually his physical condition grounded him and he returned to infantry duties as a Captain in command of the 7th company of a Foreign Legion regiment on the Somme. The 33 year old Capt Do-Huu was killed on 9 July 1916 leading an attack near Chancelier and buried at Dompierre. In 1921 his brother Colonel Do-Huu Chan brought his remains back to Vietnam and re-buried them in the garden of his ancestors at Cholon.

When urged by his friends and relatives not to be so daring and reckless Do-Huu would say that it was necessary for him to be doubly courageous because he was both French and Annamite. His tombstone in France had reflected that - 'Capitaine-aviator Do-Huu. Died on the Field of Honour. For his fatherland Annam. For his country of France.'  

Image credits: Heading photo via web; postcard via web; Blériot plan Flight magazine circa 1910; Deperdussin image Flight magazine circa 1914; Lambert hydroplane Automotor magazine .          

  

Tom Hall's Comment & Associated Ideas ~ A Response

Here is the response to Tom's interesting comment about the perrenial subject of the early Zero colour.

TH: Nick, won’t you comment on the article in Gakken’s Rekishi Gunzō for February 2018? 

I have not read it yet, although I have been made aware of those new ideas from various other sources. (Ed. I've since read it)

TH: The article ostensibly states that the paint of a Mitsubishi-built Zero was tested at a fairly prestigious lab for cultural properties in Japan. That lab found only two pigments in the top layer of paint: white and black. (This test was just for a Mitsubishi-built machine.)

Samples from just one machine tested? And if black and white pigments were identified did the article state what they were? There are several types of black and white pigments which can result in significant differences in the resultant grey colour. Did the lab reveal the nature of the paint binder? I understand (and I might be wrong) that the paint sample(s) examined are from A6M2  Houkoku-515 which had lain exposed in the New Guinea environment for 66 years. If so the residual components of paint on the airframe are unlikely to represent the original and are possibly contaminated by other intrusive elements. The absence of evidence of certain pigments (or tinters) might not be evidence of their absence. Even with Raman microspectroscopy the results are not always absolutely conclusive. 

TH: White and black in the right proportions can make J3. 

So you say but how do you know? The swatches of J3 in the Kariki 117 document and the Kugiho 0266 report do not appear as pure neutral grey. It is quite possible that the swatches have yellowed with age producing their current appearance and that originally J3 was indeed a pure neutral grey. However, GSI (Gunze) Mr Color 35 (IJN Gray Mitsubishi) as measured is not a pure neutral grey. Without knowledge of the official formula for J3 it would be bold to assert that black and white in the right proportions can make J3!

TH: However, to get a shade of khaki, you need additional pigments; or there must be damage to the paint that changes it from a neutral grey to a shade of khaki; or you need different lighting; or there must be some combination of the three. 

Khaki is your word not mine. I would prefer amber grey - a grey paint with a slight amber or yellowish tint as well as a fugitive olive undertone. That seems more consistent with the Kugiho 0266 report which describes a tinted grey. Your brief summary of how to get khaki and what can happen to paint and the pigments in it is overly simplistic. May I refer you to 'The Chemistry and Physics of Coatings' by A R Marrion, published by the Royal Society of Chemistry in several editions. That will provide a better introduction to and understanding of the multiple factor complexities of the subject.  There you will also learn about sacrificial anode pigments and tinting dye-like pigments, amongst many other fascinating scientific facts about paint technology, rather than ideas about it where enthusiasm to find something new might romp ahead of established science. . 

TH: Mr. Taizō Nakamura has demonstrated that lighting with a flash for a camera can produce the sort of gold tones that would qualify as “ameiro”. 

How the paint surface might look under different forms of illumination has no bearing on the constituent polymer of the paint or its colour values when measured. Rather the reverse is true - the polymer will determine how metamerismic the surface appears. And I do not believe that the Kugiho 0266 authors were making flash photographs of the paint inside their hangars in order to describe its appearance. But please read on.

TH: So, when the Japanese naval officer said in a footnote that the Zerosen then in use was J3 and had some ameiro, he was exactly right. He was referring to an unusual finish that exhibits a lot of metamerism.

Yes, well, I have no disagreement with the paint being prone to metamerism - it very much is - but there is more to the naval officer's description than simply a 'footnote'. When you commented on the translation of that 'key passage' in 2005 you agreed that the meaning was that the paint 'has somewhat of an ameiro tint. In other words, a warm gray as opposed to a cold one'. You also asserted that the 'genyo' (sic) in the statement referred to the Zero rather than the paint. 

In fact there are other references throughout the report which make it clear that 'genyo' refers to the paint and that it was not simply J3. The 'genyo' paint is referred to as 'ameiro' throughout the rest of the report. In the report's recommendations the Head of Kugiho states (Exhibit A):-

'At present, my opinion is that we may continue using the currently used ameiro'

And it appears distinct from J3. One of the test aircraft - Yo-105 - was specially painted with J3 for the trials, described as hai iro (ash colour - grey) and another - Yo-107 - painted with J3 and D1 (Deep Green Black colour) in patches. The J3 chip in the report shows a slightly greenish-grey appearance similar to the J3 chip in Kariki 117. The methodology used in painting all five trials aircraft is described in the report as follows (Exhibit B):-

'The paint is camouflage paint: Standard Chi-57A, Type # l.  The paint was applied directly over the currently used ameiro.  The film of the paint was rendered matte ['frosted'] and was produced by adding talc or clay powder without making the paint body coarse.'

In other words the test paints, including J3 and J2 (described in the report as blueish grey), were not the existing factory-finish colour of the A6M2 aircraft being used in the camouflage trials. They were paints applied over the existing amber grey finish. The report is dated February 1942 and I do not believe that the authors were referring simply to the effects of metamerism (which would vary anyway) when they consistently describe the paint as ameiro.  Occam's Razor tiptoes into the room at this point, hopefully not to become an elephant.

I've recently had correspondence from a Japanese interested party who went to extraordinary lengths to try to prove that ameiro as referenced in the report meant a grey colour tinted to become light blue green as a result of adding clear yellow. He also asserted that the amber grey explanation in Japan is not popular - which doesn't make it wrong.  It seems that the starting point for some is to want to believe in an absolute grey paint as a preference with the evidence being marshalled to try to prove that, rather than an objective analysis of all the evidence to draw a reasonable conclusion. The former endeavour involves either disregarding the Kugiho 0266 report entirely or attempting to distort its rather obvious meaning to mean something else.

The report's description is also consistent with the appearance of extant paint samples from several different aircraft as examined by different researchers in the USA, Japan, Australia, Canada and the UK. Mr Nakamura himself has shown extant paint samples of his own juxtaposed in comparison to the JPMA colour deck chips C27-50D and C27-60D. Those two chips are also matched to Munsell colour values 7.5 Y 5/2 and 7.5 Y 6/2 - Munsell Y = Yellow - and neither neutral grey nor grey-green. 

Most of the samples physically examined by those various researchers were originally collected and stored more or less contemporaneously with the particular aircraft's demise. As such they have not been exposed to UV light or the resultant photo-chemical activity and retain much of the paint's original integrity. The binder in six A6M2 and A6M3 examples, analysed in two other fairly prestigious laboratories, is consistently identified as a plant-type resin modified with styrene. The resin is made from the sap of trees now called Toxicodendron vernicifluum, also known as Chinese laquer tree, Japanese lacquer tree or Varnish tree. The old name for it is Rhus verniciflua. The 'urushi' type varnish made from the sap is naturally amber to dark brown in untinted form and will darken and brown further with age without UV exposure. It would have an immediate tinting effect on a paint containing a predominant quantity of white pigment.  The combination with black and yellow-brown anti-corrosive pigments creates the fugitive olive undertone but there are multiple influences going on there as the paint ages in storage. The styrene modified resin binder forms a thin film which air cures and cross links to create a very hard and durable surface as new, almost like a ceramic. But the majority anatase form of Titanium Dioxide (white) pigment in the paint compromises that durability because it is so prone to chalking. The paint also incorporates magnesium silicate (talc), an extender with reinforcing properties which improves the impermeability of the paint film (but also exacerbates chalking). With exposure to UV light the amber tone would gradually bleach out as the top surface of the paint absorbed radiation, the amber tinting preserved only in the underlying and chalking protected paint strata where it would gradually become slightly darker and browner. Was that process deliberately intended? Dunno! But the paint is by no means crude in its composition.

The dope on the fabric components of the Zero is cellulose acetate butyrate which is clear and does not readily yellow with age. It also contains triphenyl phosphate which is a plasticiser and fire retardant. There would be no need for anti-corrosive protection of light metal in the fabric dope. That is one explanation for the different tones of rudder, ailerons and elevators apparent in some monochrome photographs, also suggesting that the amber appearance of the metal paint is not simply age related degradation.

Also, Jim Lansdale has metal artifacts painted in J3 which show no sign of becoming amber or olive grey in appearance.  

It is quite possible that some aircraft were painted or re-painted plain ol' J3 from stores on repair or overhaul by Japanese naval units, especially perhaps in training units, whereas Mitsubishi applied a more complex anti-corrosive factory finish. In 2008 an artifact from s/n 3647 said to be from V-103 in Saburo Sakai's own collection was compared to Munsell N 5.5 (N = Neutral).  That's quite a dark grey - not far off FS 36251! Did Sakai do something to it? And Owaki-san once presented a piece from A6M2 W1-187 which he compared as close to FS 16314. When taken together with all the other artifacts they are the exceptions rather than the rule.  

By the way, have you raised your interesting neutral grey suggestion with David Aiken or were you being 'target specific'? ;-) David promotes a distinctive and rather bright light grey-green for the Zero, not far off RAF Sky, which is rather harder to reconcile with both your neutral grey idea and the tangible scientific facts accumulated from many extant samples.  Maybe it's that metamerism again, an idea which appears as a convenient fig leaf in order to promote any colour desired. 

Post-Blog Note. Since writing this response I have received a translated summary of the Rekishi Gunzō article referred to by Tom. Contrary to his suggestion of paint samples from a Mitsubishi-built Zero being analysed, it reports analysis of the 2-6 paint chip from the 8609 standard (the successor colour to J3) by Dr Hashimoto of the Tokyo Cultural Properties Research institute, with a presumption that J3 was the paint colour applied to the Zero. In fact no black pigments were identified in the analysis and the other chemical elements identified included more than just white pigment. The relevance of the 1945 2-6 chip to the early A6M2 paint finish is moot, although it has been reported as identical to J3, for the reasons described above.  

Disclaimer: Nothing in this blog article is intended to prevent or discourage anyone painting Zero models or illustrations in any colour they might wish to. 

References: Yokosuka Kaigun Kokutai (KuGiHo) Report No.0266 Revised Translation November 2010 via James F Lansdale

CAL# 5370 Conservation Analytical Laboratory Report on A6M3 paint, Smithsonian Institution, May 1992  

Molecular Microspectroscopy Laboratory Report, Department of Chemistry and Biochemistry, Miami University, January 2006. Paint samples tested from A6M2 Lt Iida PH, A6M2 Lt Iwama Midway, A6M2 PO1/c Shigenori PH, A6M3 c/n 3023 Buna, A6M3 c/n 3268 Lae, A6M5 USS Lexington (Kamikaze) & B5N2 F1/c Kitahara PH  

Painting the Early Zero-Sen by Nicholas Millman, self-published 2011.

A6M Zero Painting Guide by Ryan Toews, unpublished thesis, 2011.

Paint samples loaned to author for analysis and measurement by James F Lansdale, Bob Alford and Greg Springer. 
Degradation models © 2018 Aviation of Japan

 

 

Piebald Army Tanker by Dan Salamone

Dan Salamone, continuing his innovative foray into Japanese airfield vehicles and equipment, has very kindly shared these images, of work-in-progress and completed model, of his skilful conversion of the 1/48 scale Hasegawa Isuzu TX40 fuel truck (Kit # X48-14) with fabric roof cab into the steel cab version. The unusual dazzle painting is based on a colour photograph taken at Kumanosho near Kumamoto city on Kyushu, a 6th Air Army airfield used for operations against Okinawa. 

 In Dan's own words then. . .

"This is my completed 1/48 Hasegawa TX40 steel cab truck conversion project. After finding enough photos of the real vehicle, I started converting it from the fabric roof version as molded in the kit. Evergreen styrene was used for the various parts, the roof is styrene sheet laminated and glued together, then cut and sanded to shape.      

The fuel tank itself in the images I was using as reference showed a smooth surface rather than the ribbed version as molded in the kit. I sourced the fuel hose from my LHS (as was the kit and all other finishing materials).

I used custom mixed Vallejo acrylics for the camouflage, then weathered with artist's oils, AK pigments, and Vallejo washes and acrylics. The final clear coat is Gunze Mr. Super Clear matt, from a spray bottle. 

Normally these vehicles were painted in overall IJA Khaki, however, a series of post war color images show a collection of various fuel and starter trucks left at a base along with some Ki-67 bombers*. The trucks were all painted in a variety of bright “dazzle” schemes, and make for a very unique modeling subject."

*The Ki-67 bombers appear to be from Hiko Dai 110 Sentai which ended the war at Kumanosho (隈ノ 庄). The 110th was formed in October 1944 at Hamamatsu under Major Takeo Kusakari (who survived the war) with only two chutai throughout its existence. The unit conducted bombing raids against Saipan, losing six aircraft on the night of 7 Dec 1944. In an 8-day period during early February 1945 the unit transported 30 tons of material to Iwo Jima via Tachiarai in preparation for the expected  US invasion.  After the invasion began it engaged in daring low-level nocturnal attacks against shipping and landing areas. In one of these attacks on 21 February the tail turret of Lt Nino Sonoda's aircraft was blown off by anti-aircraft fire with the gunner Sgt Jusaku Saito falling to his death. Sonoda managed to fly the badly damaged Ki-67 back to a forced landing offshore at Hamamatsu  On 6 March a Ki-67 was lost attempting to transport replenishment ammunition to the island whilst fighting was in progress (1Lt Kazuo Sakonji MIA). The 110th then moved to Kumanosho on 18 April to conduct attacks against enemy shipping off Okinawa and later against Okinawan airfields. That airfield, although designated for twin engine bomber operations, proved unsuitable for heavily loaded take offs and the aircraft instead sortied for operations from Kumamoto airfield where Hiko Dai 60 Sentai was based. A total of 20 aircraft were lost in those operations, several from forced landings at sea, and seven chutai commanders were killed in action, with the 1st chutai bearing the brunt of five consecutive commanders being lost. At war's end the 1st chutai was commanded by Captain Tatsuhiko Kishimoto and the 2nd by Captain Akira Suzuki. 

With special thanks to Dan for sharing his images and write-up of a brilliant and unique model.

Image credits:- All model photos © 2018 Dan Salamone; Kyushu map © Google Maps

References: Japanese Army Heavy Bomber Units by Dr Yasuho Izawa; Air Operations on Iwo Jima and the Ryukus (Japanese Monograph # 51)/

IJN Type 99 Air-tro-Air Bomb

Here are data sheets for the 'Mk.3' air-to-air bomb included in the new Fine Molds C5M2 kit - in case anyone was wondering! Although Fine Molds call this a Mark 3 bomb its correct designation was Type 99, No.3, Mk.3, Mod.1 bomb. The additional body fins were required for arming the clockwork tail fuse. 

 

The US Intel sheet says the additional body fins were to accelerate the bomb whilst the RAAF bomb disposal sheet says they were to slow down rotation, to stop the bomb bursting prematurely when it reached 1,000 rpm. The fuse burst the central charge and scattered white phosphorous filled steel pellets which ignited on contact with the air. 

 

 

The sheets also provide asdditional colour details. The Type 99 was an air-to-air bomb intended to be dropped over bomber formations per the Fine Molds box art but the sheets also imply an air-to-ground use. There are several photographs showing the resultant white 'jellyfish' type air burst (heading photo). 

Image credits:- National archives

It's Not That It's This! No It's Not! Etc.

Recently a friend of mine wrote that he was tired of The Great Zero Colour Discussion because people will continue to illustrate white Zeros regardless!  So true and I can understand his weariness. I thought about it on seeing that the latest Fine Molds Mitsubishi C5M2 kit (now available) recommends GSI (Gunze) Mr Color 35 IJN Gray Mitsubishi for the overall finish. Those stubborn purveyors of RAF Sky-like grey-green for the Zero will be disappointed because that paint is actually a rather bright, light, slightly blueish grey. 

The sample of Mr Color 35 paint that I measured in 2010 was a Munsell B - Blue - 4.7 B 6.4/0.8. Interestingly the Hobby Color version H61 IJN Gray measured at the same time as a Munsell GY - Green Yellow - 8.9 GY 6.2/0.7. I haven't tested more recent bottles but it appears that H61 in the new bottles is now closer in appearance to the light blue grey of 35.  Both Munsell values indicate very low blue colour saturation, or chromacity, from neutral grey. And the perception issue of low saturation blue or green undertones is well established. Some might perceive more green, others more blue.  

 In 1972 Matchbox suggested FS 37875!

That Munsell value for Mr Color 35 is interesting because both the closest FS 595 and RAL values are at exactly 1.69 in difference where < 2.0 = a close match. However they travel in slightly different directions. FS 36373 is a Munsell BG - Blue-Green, again of very low saturation, whilst RAL 7040 Fenstergrau (Window grey) is a low saturated PB - Purple-Blue. Pigments for 36373 are rutile (non-chalking) titanium dioxide (white), phthalo blue (red shade), natural raw umber (a dark, slightly greyish brown) and carbon black (blue shade). If you look at one and not the other, without looking at 35, they will mislead, despite their closeness.   

Zero replica from Eternal Zero (永遠の0 Eien no Zero) 2013

The idea of a light blue grey for the Zero seems very strong in Japan and appears to have made a comeback for modellers after popularity in the 1980s - although not with the makers of the Eternal Zero movie. The surface of the real paint does in some cases shift towards a light slightly blueish grey as it chalks* and degrades from glossy to dull matt. Most of the argument for light blueish grey as the original factory colour seems to be the emotional, personal choice kind (it does look smart on a Zero model) where the preferred colour is settled on before the evidence is marshalled and any inconvenient contradictory evidence is simply disregarded. 

Another idea promotes the grey-green colour, infamous as hairyokushoku (ash green colour), which in the minds of its adherents somewhat resembles RAF Sky, a cool, minty light green with a slight blueish undertone. Or maybe that's a cool light blue with a slight minty green undertone? Usually those arguments come with images lifted from online GSI or Tamiya colour charts or photos of models from Tamiya adverts (above), or rely on the semantics of colour descriptions - ambiguous at the best of times but even more so in Japanese. Rarely if ever do they incorporate physical analysis of the real paint - let alone the scientific measurement of it. Both ideas are more wishful thinking, if not a cult, than science.  And we are well into an era of post-revisionist revisionism where fad often defeats fact.

Tamiya XF-76, which in colour charts and their own model adverts often appears to support the minty grey-green brotherhood, is, as measured (and sorry to disappoint), a Munsell Y - Yellow.  It is slightly more greyish than the Zero factory paint - at a difference of only 3.67 - being something of a compromise between the original amber-grey appearance and a slightly oxidised and chalked appearance, or, alternatively, between  J3 leaning slightly towards ameiro and plain ol' J3. Note especially that it has an identical Munsell lightness value of 5.8. The pigments and their ratios in XF-76 paint are as follows:- Titanium Dioxide (white) 16.5%, Pigment Green 7 (Phthalo Green) 0.2%, Red organic 0.2%, Yellow organic 0.5% and Diatomaceous earth 0.7%. Pigment Green 7, although a strong tinting colour (despite being transparent), is known to darken and dull with long term exposure. The red and yellow organic pigments are not specified and there are several different types. Diatomaceous earth is a naturally occurring silecious sedimentary rock ground into a fine, off-white powder used as a filler and matting agent.  XF-76 is perhaps more representative of a moderately weathered aircraft in service for several months. Depending on lighting it can appear browner or greener, brighter or duller in online model images. 

Tamiya XF-14 (IJA Grey) is intended to represent the JAAF paint colour  # 1 Hairyokushoku (ash green colour) and is often suggested as the basis for the Zero colour in the erroneous belief that the Army and Navy paint colour standards were identical. It is actually further away from the original paint colour value than XF-76 and there is no comparison between the Army colour # 1 Hairyokushoku and the Kariki 117 ‘M’ series Hairyokushoku beyond the common name (# 1 vs M1 are at a difference of 20.1). The pigments in XF-14 are Titanium Dioxide 17.7%, Carbon black 0.1%, Pigment Blue 15 (Phthalo Blue - type unspecified) 0.1%, Pigment Green 7 0.1%, Red Organic 0.1% and Yellow organic 0.5%. XF-14 might be considered by some to provide a reasonable out of the bottle representation of 'scale colour' on a moderately weathered aircraft but it also lacks the distinctive amber undertone. Hopefully the relatively subtle differences in the Zero colour, IJA # 1, XF-76 and XF-14 will be apparent from this presentation.  

Ameiro ~ The Culprit

あめいろ 【飴色 · あめ色】noun:  amber;  yellowish-brown

'Ame iro' - a colour - has a quite different sense to 'ame' alone which also means rice jelly or candy. For most Japanese there is indeed a 'sense of transparency' in this term (which might have given rise to the idea of a clear varnish applied over grey paint, ambering as it aged) but it is also used to describe an opaque, solid colour.   So when the author of Kugiho 0266 described a grey colour leaning slightly towards amber/yellowish brown colour he was probably not describing a grey turned blue-green in appearance by the addition of clear yellow! 

If he wished to describe a light grey-green colour then it would have been far less ambiguous to refer simply to hairyokushoku for which the IJN Kariki 117 already had the established colour standard in the 'M' series. In fact one of the test aircraft (Yo-151) used in the camouflage trials recorded in the 0266 report was specially painted overall in M1, described in the report as pale green colour (see above). However that was not the colour described by the author throughout the rest of the report as gen'you (currently used) ameiro (amber colour) for the factory finish of the Zero.

Kariki 117 also had an established standard for blue-grey colours - the 'K' series described as kaiseishoku - but the author of 0266 referred to J3 ash/grey colour, any blueish undertone for which is unproven. The measured standard chip for J3 (and its successor colour 2-6) being a Munsell GY - Green Yellow of very low colour saturation. The slight greenish undertone of the chip could well be the result of age related yellowing and it is conceivable that J3 was originally a more neutral grey, but that does not substantially alter the effect of adding yellow-brown pigments to it.

Astonishingly, the extant paint appears exactly similar to the description grey colour leaning slightly towards amber colour and that description is absolutely consistent with the quantifiable attributes of the pigments and binder which it incorporates. But as my good friend observes, nothing will change and personally subjective ideas of how the colour ought to look will proliferate, as with all opinionated twaddle** on the internet. 

One last thing to always bear in mind if undecided. Ignoring evidence does not mean that it doesn't exist.

*Chalking 

The polymer of the paint surface is degraded by a combination of heat, moisture and light resulting in a powdery, greyish-white pigment or patina forming on the surface. This type of degradation is exacerbated by certain types of white pigment, for example the anatase form of titanium dioxide, as well as by common paint fillers and extenders like China clay. Titanium dioxide is both a UV-activated oxidation catalyst and a UV absorber. Free radicals are formed at the surface and then oxidise the paint binder by photocatalytic degradation. This reduces the gloss and produces a friable layer on the surface of the paint film - "chalking". In effect the titanium dioxide pigment and any extender particles are being 'released' from the fractured binder to form a greyish-white powdery patina over the surface of the paint. That has the effect of dulling (de-saturating or washing out) and greying the appearance of the underlying colour and is often mistaken for colour fading. The powdery residue, like fine chalk dust but usually slightly greyish rather than pure white, will appear on the hand when rubbed across the paint surface. A diligent maintenance regime can reduce it but in certain environments it cannot be prevented. Many wartime colour photographs of aircraft reveal severe chalking of the paint surfaces, often misidentified as the 'real' colour.    

** Twaddle - trivial or foolish speech or writing; nonsense.18th c an alteration of twattle (1556), of unknown origin.

Image credits: Heading photoof Zero replica Martial heland via Wiki; Matchbox Zero box art © 1974 Lesney Products plc via Scalemates; A6M2 'Eternal Zero' replica via web; Tamiya 1/32 A6M2 image © 2003 Tamiya Inc.;Rendered colour chips © 2018 Aviation of Japan