Weathering question
Japanese aircraft paints
by François P. WEILL
Were Japanese paints really of lower quality than Allied paints ?
Was this the cause of extensive paint chipping as seen on many Japanese aircraft photos ?
Were all services and all aircraft within these services concerned ?
It has been often said that legends and myths have a grain of truth behind them. The myth of the “inferiority” of Japanese paints in WW II likely originated from the truly appalling state some Japanese paint jobs reached. The reason commonly cited was not the actual cause. Japanese aircraft, even after some service, did not necessarily lose their paint any more than comparable planes used by the Allies. Let’s now examine what caused the myth and how it should affect our attitude as modelers when completing a Japanese subject.
To better understand the problem, it might be necessary to know some basics in aircraft finish and to consider that the period that interests us, broadly 1932 to 1945, was in some respects a period of quantum leap in aircraft design.
In the early 30’s, most airframe construction was basically a refinement of the techniques used during WW I and the 1920’s. Although wooden assemblies had been generally superceded by metallic frames, most planes were still fabric covered. Ten years later, the overwhelming majority of combat planes were entirely metal covered.
Like all tissues, fabric is liable to absorb a fair amount of moisture and in so doing to augment its weight considerably and sag badly. During the fabrication of a fabric covered part, care was required to maintain sufficient tension through the material to obtain a smooth surface. The use of a tension and waterproofing substance was mandatory.
This was ever achieved through the use of many layers of tension varnish, which as a side benefit also waterproofed the fabric. Originally this product was as clear as the varnishes of the time would allow (in fact it was slightly amber in tone). For modelers this shade is well known by names like “clear doped linen” and this varnish became known in aviation terminology as dope.
From this explanation, it can be seen that the first reason to apply a finish to planes was purely technical. Doping also provided the material covering the airframe a degree of  protection from the elements. In these early times, as military aviation was almost non-existent or in its infancy, questions regarding the benefits of concealing an airplane were not in the order of the day.
With the development and growth of military airpower during WW I, some solutions were developed to help conceal aircraft from the enemy. Among the Allied Powers this was generally achieved by introducing appropriate pigments into the external layer or layers of dope. The German used a slightly different method, printing the camouflage pattern on the actual tissue itself, then using clear dope over this fabric as usual. Thus aircraft camouflage came to life.
After WW I, budget restrictions came over the military establishments in the world and rapid introduction of new types became a rarity. Short service life of an airframe became undesirable, and it was found that the dark tones used from WW I camouflage were not only unnecessary but shortened the life of the airframe. The dark tones concentrated the heat of the sun, leading to damage of the frail assemblies (most were still made of wood in the early 20’s) by creating dangerous deformations. Most air services throughout the world discarded these dark pigments and switched to much more reflective light ones.
In Japan, the IJNAF and the IJAAF didn’t solve this problem the same way. The IJNAF had been deeply influenced by the British and had used a green over clear dope scheme similar to the British system. The IJNAF chose to switch to silver dope and the IJAAF began to use a gray-green pigmented dope as standard finish. Strictly speaking, this was not a camouflage finish. Both finishing coats were nonetheless absolutely comparable in quality to worldwide standards and the current state of the art.
Around the mid 30’s airframe construction in the most advanced designs switched from fabric covered construction to riveted light aluminum alloys.
Unlike iron or steel, aluminum alloys do not exhibit signs of rapid and visible oxidation. Surface oxidation is still present and shows as a matt grayish coating, but as soon as it is rubbed and properly cleaned the aluminum becomes again smooth and shiny. Nonetheless, it was discovered that aluminum could be affected by a more dangerous and insidious form of oxidation, called inter-granular corrosion, in the form of almost microscopic black spots which literally eat the metal and make it fragile and brittle. The cause was not the aluminum itself but rather impurities in the metal. To combat this problem, the aluminum alloys were coated by an almost 90% pure aluminum called “Alclad”. This technique was known to the Japanese, who used it extensively.
This protection was only partial, something they were soon to discover, and just delayed the inter-granular corrosion, which was made worse when aircraft were exposed for any length of time to the salt atmosphere of the sea.
The attitude toward the finish of the new all-metal aircraft differed between the IJNAF and the IJAAF. Strangely enough, the IJNAF, for whom the salt atmosphere of the sea was their normal environment, changed their practices according to the new technology and didn’t use any protective paint over the Alclad surfaces. Perhaps this was because the appearance of the aircraft with this finish was similar to the silver doped birds they were accustomed to, or perhaps because it saved manpower hours, raw material and weight. The IJAAF on the other hand, stayed with its policy and continued to use the regular glossy gray green finish on their newer metal-covered aircraft. This finish was applied at factory level, and was therefore applied using “state of the art” methods with a proper priming coat. In photos of these aircraft no particular paint chipping is noticeable. In both services, fabric-covered control surfaces and similar parts were treated as before, according to each service’s standard color scheme: IJAAF planes were glossy gray-green and IJNAF planes silver dope.
Sino-Japanese War and the return to camouflage
The Japanese intervention in China was met by unexpectedly stiff resistance in the air. Defensive camouflage was introduced when Japanese aircraft came under attack once they began flying from airfields on the Chinese mainland and from shore bases that were established for floatplane units. The role of the IJAAF was minor at this time when compared to that of the IJNAF planes, and camouflage was first reintroduced on Navy aircraft. This was to be known as “Kumogata” scheme, composed of brown with irregular dark green areas on the upper surfaces similar to the camouflage adopted by the RAF[1].
There were still many fabric-covered floatplanes, biplane torpedo-level-bombers and dive-bombers in service. This camouflage, applied in the field, bonded well to the original silver dope and no particular chipping is noticeable. This is not the case with the all-metal IJNAF types, which exhibited extensive and rapid peeling. This clearly demonstrates an important point — the paint itself was not the cause for the extensive peeling, the true reason was simply that the application of the paint in the field was done without primer.
When camouflage was applied to some of the IJAAF aircraft, this was painted over the factory-applied standard gray-green (except for foreign aircraft like the Fiat B.R.20 which were delivered in the original camouflage schemes) and when looking carefully at photos of these planes, hardly any abnormal paint chipping is visible.
Once the Japanese had established air supremacy at the end of 1938, the IJNAF was quick to abandon the systematic use of camouflage, except for long-range bombers which still operated unescorted (and suffered significant losses at the hand of Chinese fighters). “Peacetime livery” had returned.
In the meantime, the IJNAF was learning the hard way about exposure to salt air. The US Navy had better anticipated this in keeping all its “metallic birds” silver painted and not bare metal. Japanese bare-metal aircraft in salty atmosphere were adversely affected by inter-granular corrosion, despite the use of Alclad. The Nakajima B5N,  for an unknown reason (better Alclad treatment ??), was not affected to the same degree. Only the Type 97 Flying Boat entered service already finished with an overall finish of
silver paint.
The way the IJNAF coped with this new problem for one of its mainstays of the period, the Type 96 Kansen fighter, is still under much debate. Anyway, some anti-corrosion measures were taken, as the appearance of all-metal carrier aircraft changed, and fast. There were no more bare-metal aircraft, apart from the B5N, and coated surfaces became clearly apparent on aircraft finished in “peace time livery”. For example, the Type 99 dive-bombers were obviously covered with the same kind of silver paint (with a smooth but not mirror like finish) that was used on the contemporary metallic seaplanes. We won’t elaborate here on the real nature of the Type 96 Kansens finish, suffice to say that it gained a mirror like finish with a metallic appearance instead of bare metal. But soon a new finish was to appear…. Anyway, during the War in China, only the field-applied Kumogata camouflage was prone to extensive peeling when used on metal-skinned airplanes, as shown by available photos. We know now it was because of the absence of primer.
As far as the IJAAF was concerned, there was no noticeable modification during those years and the Ki. 27s engaged in the Nomonhan Incident (Khalkhin Gol) were still finished in the plain traditional glossy gray-green
Policy changes
Anticipating a probable broader confrontation, the IJNAF then decided that its next standard shipboard fighters would inaugurate what we will now call an “air superiority scheme” or an “offensive camouflage”.
The author believes that this camouflage was not at first defined precisely. It is known that the first A6M1 12-shi prototype was painted gray-green. There is no clear explanation for why the first operational A6M2 Model 11’s of the 12th Ku. In China were visibly treated in two tones of paint. The rear part of the fuselage and 2/3 of the external part of  each wing were clearly lighter and matt, while the rest of the plane (excepts the regulation black cowl) was glossy and darker.
The outcome was a glossy gray-green scheme which — all manufacturers variants included and most probably the majority (if not all) of the B5N’s excepted — was to become the standard scheme in first line units of the IJNAF when the Pacific War broke out, for all planes except the big multi-engine bombers and flying boats, which kept the earlier silver finish, and older types not in production and scheduled to be phased out.
This new glossy gray-green scheme was factory-applied with state-of-the-art techniques over a red brown primer, and it proved to be extremely resistant. No plane so painted is likely to exhibit any extensive peeling, even under harsh conditions. There is one photo of a much used Mitsubishi F1M2 in a later period with the green camouflage paint of the upper surface well worn (though not really peeling), and with the central float almost stripped of green paint by the abrasion of the sea, and which still retains a nominal matted coat of the gray-green paint. This author would not hesitate to qualify this glossy gray-green as one of the best and more resistant paints in use during this period by any belligerent. This is quite a far cry from the legend of the inferior quality of Japanese paint.
On the other hand, starting with its new Type 1 single engine fighter (Hayabusa), the IJAAF adopted a much simplified factory scheme for all single seat fighters. This factory finish was to be completed by front line units with the application of appropriate upper surface camouflage. The factory scheme consisted of a bare metal finish with only the fabric covered control surfaces treated the old way in glossy gray-green, an antiglare panel and the Hinomarus (at this time still applied only in four wing positions). This policy was in place for these aircraft up until the end of 1944, except for fuselage Hinomarus when these became mandatory sometimes in 1942. Much later, and only for a limited period, some multi-engined aircraft like Ki 49 Donryu were delivered to squadrons in Alclad finish, but this remained more an isolated case than the rule. As a general rule, until late 1944 multi-engined IJAAF planes were painted in the factory with a primer undercoat and an overcoat of the traditional glossy gray-green.
Single-engined fighters were sent out to frontline units without a prior application of primer. It was there, at the unit level in the field, that the camouflage was completed. Initially the most common scheme used was a solid coat of Jungle green, then all variations of blotches, stripes, and combinations of two or more colors were used on these planes. IJAAF camouflage colors were used mainly, but sometimes mixing produced non-standard colors, and the use of captured paint was also allowed. The important thing is that the lack of primer generated a lot of paint chipping and peeling, to the point where it has now been established that some artists’ renditions of planes in a blotched camouflage were in fact misinterpretations of a solid color coat that had peeled to the point where it looked like this “blotching” was done deliberately !
In contrast, multi-engined aircraft, finished in the factory with glossy gray-green and then camouflaged in the field with whatever pattern was in use by their unit never became so worn. They weathered just like Allied aircraft in comparable climate, or even less considering the durability of the gray-green paint, which apparently had the same qualities its Navy counterpart had. At the same time, the few types delivered to the units in an Alclad finish weathered the same way that single-engined fighters did. Of course, the climate and the conditions of the aircraft’s use played a role, but all in all the main difference in the way that Japanese aircraft weathered, when compared to Allied aircraft, was not a question of paint quality but the presence or absence of a priming coat.

Meanwhile in the IJNAF
At the time of the “Hawaiian Operation”, the offensive camouflage already described was standard for shipboard planes in first line units. With the exception of the Nakajima B5N2 Model 3 torpedo-level bombers, the glossy gray-green paint clearly predominated. Kates[2], even when camouflaged with the makeshift schemes that were the rule during this first day of the war, were painted without any primer and later were to exhibit a high degree of paint peeling. (See the photo of Fuchida’s plane during the operation against Ceylon, which was taken a not much later.)
Very soon this camouflage was considered unsuitable for all planes but the Zero fighter. Despite the continuous string of victory, a kind of standard, non-factory, “sea compatible” defensive camouflage developed. This consisted of the application of a solid dark green coat on the uppersurfaces, and this solid coat was even sometimes applied at sea aboard the carriers. The main aircraft concerned were all-metal floatplanes (Jake, Pete), Type 97 torpedo-level-bombers and Type 99 Model 11 dive-bombers, but this later extended to almost any aircraft other than shore or carrier based single-engined fighters. Although not applied at the factory, these camouflage finishes were usually applied on glossy gray-green factory painted aircraft, and soon the Kates also received a systematic application of underside gray-green. For a while, until this scheme began to be applied in the factory, the Kates remained subject to the peeling associated with the absence of primer. Some older model aircraft kept their pre-war finish even in first line service, like the 96 Kansens Model 4, and a few of the older sea or land-based fabric-covered biplanes were still in Kumogata. Heavy bombers 96 Rikkos (Nells) or Is’shikirikkos (Bettys) were still delivered unpainted as before, then painted in the Kumogata scheme at unit level, without primer as before and with the same consequence as far as paint peeling was concerned. Eventually even the flying boats got their “war paint”, a solid coat of dark green. It is difficult to know if the undersurface were really treated with a gray green under surface color, as a recent ModelArt book on the subject suggests. As usual, B&W pictures are impossible to interpret on that point. The author’s opinion is that the original silver paint was - for the H6K’s - the most probable finish for the undersurface, at least for aircraft receiving the dark green solid coat in the field. Despite difficult conditions of use, the fact that this planes were painted at unit level did not affect the durability of the paint used since the original coat was always applied on a primed surface. When compared to USN Catalinas for example, paint weathering and peeling is not any more evident on Japanese flying boats.
The situation had not changed significantly when the Solomon campaign began, however, except for the Zero fighters, the application of a solid dark green coat was about to begin as part of the manufacturing process. Heavy bombers kept the Kumogata scheme for a while, into August and September 1942. With the arrival of factory finished Bettys, the planes in Kumogata scheme were more often than not retouched, their brown color being covered by green (but so badly as the original scheme is often visible) and once again, applied on an unprimed coat of paint, extensive peeling continued. New Bettys arriving with their factory-applied dark green paint on the uppersurfaces and bare metal undersides were not as prone to peeling. A sample from the Jim Lansdale collection shows red-brown primer was present under the green coat despite the bare metal undersurfaces. On the other hand, some aircraft rushed from second-line units in Japan were quite different. Another Betty (a G6M1-L transport) for which Jim has a sample of fabric has a rather strange story to tell. This aircraft was obviously delivered in the bare metal with fabric covered parts in silver dope scheme (although the silver dope was applied on the red brown primer) over which a hastily-applied sprayed coat of Japanese dark green was added, later to be touched up with a brush using a much lighter green, which I suspect was Australian paint scrounged from the Rabaul facilities, in one of the worst paint jobs ever to be seen on an airplane. Another aircraft, a Type 99 Model 11 dive-bomber, obviously came from the same replacement pool, correctly sprayed in dark green uppersurfaces but still in silver dope undersurfaces. Considering the harsh conditions on these islands, and the visible differences between factory-applied camouflage finishes and the improvised camouflages, it is obvious that extensive paint peeling was characteristic of an unprimed paint job on a bare metal aircraft. Sometimes later, as 1942 drew to a close, even the Zeros in the Solomons began to receive defensive camouflage in the form of blotches, stripes and clouds of dark green paint applied over their high quality glossy gray-green factory finish. Despite the prevalent harsh conditions and climate, it is hard to find evidence of Zeros peeling.
By June 1943 the defensive camouflage of dark green over glossy gray-green paint job was systematically being applied in factories, and primer was consistently used for all types. The exceptions were big multi-engined aircraft such as heavy bombers, which remained bare metal underneath, and flying boats, which were given a protective silver (or glossy gray green ?) finish on the undersurfaces. Again, there is little evidence to show extensive paint peeling or weathering on a scale any greater than that apparent on Allied aircraft.
To the end
At the end of 1943 or in early 1944, the use of the glossy version of the gray-green paint stopped, and a much more fragile matt or semi-matt coat replaced it. This paint displayed even more variation in shade from different manufacturers than before, except for seaplanes which seem to have used the glossy gray-green much later than other types. Conditions in Japan began to progressively deteriorate both in terms of qualified manpower and raw material availability.
Large aircraft like the Betty were the first to fall victim of this situation and from the first series of G4M2 bombers, primer ceased to be applied in the factories. Consequently, G4M2s demonstrated a real tendency to peel significantly.
As the war progressed, more and more new aircraft were delivered without any undersurface paint at all. This trend to eliminate undersurface paint and to abandon primer as part of the manufacturing process was progressive and did not apply to some aircraft. Seaplanes, for obvious reasons, continued to be painted in protective finish right to the end of the war. The Zero fighters retained primer as an integral part of the production process as the gray-green was used as an undersurfaces color coat to the end of the war. The lack of high quality glossy gray-green paint rendered the Zero’s finish much more fragile,  as shown by some pictures of obsolescent (but still relatively new) Nakajima-built Model 21s which were converted to fighter bombers (Bakusen) and used for Kamikaze missions. Some peeling is evident on these aircraft, which were extensively used and generally well-worn from extensive training service in harsh tropical climates like the Philippines, but they had nowhere near the appearance as Navy or Army planes finished without primer, nor do they detract from Allied aircraft finished with the same standard. Some aircraft switched from a higher quality finish to a lower one in the midst of the production run of a given model. For example, some N1K1-J Ko Shiden in the Philippines were seen both with and without matt gray-green undersurfaces, although all seem to have been finished without primer. As there were no real regulations during this time frame, it is highly recommended to work from photos to determine the real state of the aircraft to be modelled. In contrast to earlier periods, only photographic reference will establish whether primer was used or not.
In the IJAAF, things remained unchanged until late in 1944, when at least a “standard” scheme, factory applied camouflage seems to have been devised. (The author would like to see material evidence of gray undersurfaces applied to Hayate fighters before the new standard came into effect. Some aircraft have been restored and painted in these colors based on speculation.) Aircraft produced in late 1944 were finished a brownish green tint on the upper surface, not unlike the Dark Olive Drab 41 of the USAAF in its inability to retain the original shade and susceptibility to color shift, and not far from the variations in weathering that the US paint experienced. The average appearance might be close to FS 30118, sometimes with a more greenish or brownish hue. The undersurfaces were a kind of gray with a distinct tan cast in it. This scheme was applied to all kinds of aircraft, but it appears that the way the surface was prepared varied from manufacturer to manufacturer and from aircraft to aircraft. Most single-seat fighters seems to have been painted without primer and peeled readily, others, like Ki.45 Toryus seemed to have retained a certain degree of preparation even with that scheme, as seen in photos. Not all operational aircraft were so finished by the end of the war. Some were from older production still in service, and others had been painted in nocturnal schemes obtained by extending the uppersurfaces color to the undersides. As with IJNAF aircraft, it is recommended that to model an aircraft from this late period, refer closely to actual photographs of the subject aircraft. This doesn’t change a rule we now know perfectly: the only Japanese planes to peel extensively were those all-metal aircraft which were overpainted without primer.
The alleged poor quality of Japanese paint during the Second World War is a myth, and one very difficult to give credence to considering that for centuries Japan has produced some truly splendid lacquered objects. The preconception that Japanese paint was inferior was in all likelihood brought about by the obvious peeling and chipped paint visible on many types of Japanese aircraft from both services at different periods. It is known today that the cause of this poor paint coverage was the lack of primer under the external color, a reflection on the quality of manufacturing rather than the materials. Producing an accurate and believable replica of a WW 2 Japanese plane does not automatically imply systematically simulating heavy paint chipping. If a modeler knows for certain that a factory applied paint job included primer, he should be aware that extensive paint peeling is to be ruled out immediately.
Japanese aircraft were no more likely to be subject to heavy weathering and paint chipping than Allied aircraft operating under the same conditions. The assertion that Japanese paint was of inferior quality is not at all substantiated in available documents or by existing samples of Japanese aircraft skinning. The actual cause for this heavily-worn paint is that during some periods of the war, standard manufacturing procedures omitted the application of primer, leading directly to heavy paint chipping and peeling on many aircraft — this is the background of this myth.

[1] The author is well aware of the fact that some authors believe gray J3 was used on undersurface too, but after carefully reviewing the available pictures of all metallic planes and not noticing any paint chipping, he concluded that no evidence of use of any undersurface coat is apparent and considering the fact that grayed weathered aluminum surface is not different on B&W photo rendition from a gray such as J 3, and the added complexity of field painting the undersurface, it is most probable that no undersurface specific shade was ever used with Kumogata scheme.
[2] It still remains unclear if all the Kates engaged on Dec. 7th 1941 received an undersurfaces coat of gray-green or if some were still bare metal. Evidence of makeshift undersurface painting exists but from the B&W photos it is hard to tell if some - or even the majority of them - remained unpainted on the undersurface or not…