Here''s a look at the contents of Model Aircraft Volume 10 Issue 4 (April 2011). It will be available on the 24th March 2011.
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If you have comments or questions please post them here.

Thanks!

I was a little disappointed (but not surprised) by the article on Spitfire undersides.
1/. The black/white undersides were introduced pre-war, not after the war's start.
2/. There was no such wartime colour as Eau-de-Nil 16 (which is, or rather was, a British Standards colour); there is a post-war report, by a British Standards manager, which states that they'd offered their services to the Air Ministry, whose reply was in the "Thanks, but no thanks" category, since they intended to keep control of colours themselves. There seems to have been a general assumption that, because Eau-de-Nil looked similar to Sky, they were one-and-the-same, but this was not the case. Sky was, in fact Camotint (Sidney Cotton's invention for his P.R. Blenheims) renamed by the Air Ministry. Since Titanine were Cotton's sole supplier, the initial shortages, until more suppliers could be brought into production, is entirely logical
3/. The "evidence" for Sky Grey's (a R.N. colour) alleged use seems to be the discovery of grey tail wheel legs, during a couple of "digs." I'm not sure how generally aware people are, of this, but every Spitfire part was undercoated in a light, or medium, shade of grey; perhaps consideration should be given to the idea that the top colour, over the years, has come away, or even that, in the rush of 1940's service requirements, some items were fitted with only an undercoat, and not the benefit of a top coat (one ex-609 Squadron rigger told me,"After a repair, we just slapped on any colour, green, grey, sky-blue-pink, we didn't care, so long as we got them back up.")
4/. From pre-war Sky blue had been a standard colour for use on drones like the Queen Bee, so it's entirely logical that some airfields would have had stocks, and it's also possible that (since no-one had any idea what Sky was)
some aircraft were mistakenly painted with it. .
Edgar

1/. The black/white undersides were introduced pre-war, not after the war's start.

And nowhere does the author state or even imply that black-and-white undersides were introduced after the start of the war:-

“The Aluminium scheme on the under surfaces started giving way to a new scheme of Black and White, for the port and starboard areas respectively, divided along the aircraft’s centre line in the period March to May during 1939.”

“In January, 1939, the Air Ministry authorised the adoption of the Black and White scheme for the under surfaces of fighter aircraft and the Technical Officers at Supermarine and Hawkers were informed of the new scheme to be worn by the RAF’s fighters. “

“The squadrons began repainting the Aluminium under surfaces of those Spitfires already in service during the period from March to May, 1939.”

“An interesting variation seen on the Black and White under surface scheme was that seen on No. 72 Squadron Squadron’s aircraft around April, 1939.”

“K9987, RB-V, 66 Sqn, circa May/June 1939. Spitfires were now leaving the production lines with under surfaces finished in the Black and White scheme divided along the fuselage centre line, …………”

“The Black and White production scheme already referred to was briefly interrupted when Supermarine applied a Black, White and Aluminium scheme to some aircraft on the production line. For the most part, this scheme was applicable to the batch from circa L1018 to N3032, but a handful of airframes outside this block were also given the same finish………..The Black and White scheme was reintroduced after the war began, with N3033 being possibly the first aircraft to be so finished.”

The word used is reintroduced and the meaning of the author is quite clear. The Black and White scheme was introduced to Supermarine’s production line before the war, replaced for a while with a Black, White and Aluminium scheme, and then reintroduced after the war had started.

2/. There was no such wartime colour as Eau-de-Nil 16 (which is, or rather was, a British Standards colour); there is a post-war report, by a British Standards manager, which states that they'd offered their services to the Air Ministry, whose reply was in the "Thanks, but no thanks" category, since they intended to keep control of colours themselves. There seems to have been a general assumption that, because Eau-de-Nil looked similar to Sky, they were one-and-the-same, but this was not the case. Sky was, in fact Camotint (Sidney Cotton's invention for his P.R. Blenheims) renamed by the Air Ministry. Since Titanine were Cotton's sole supplier, the initial shortages, until more suppliers could be brought into production, is entirely logical.


It has always been known that other colours had been used as a substitute for Sky; I well remember it being mentioned in magazine articles etc when I was a teenager four decades ago and it was mentioned in various additions of Camouflage and Markings, published circa 1969/70. Eau-de-Nil was one of the earliest identified, in particular that it had been used on the under surfaces of 264 Squadron Defiants. The colour in question, to give its correct name, was BSS 381 (1930) No 16 Eau de Nil. All BSS 381 (1930) colours were available before, during and after the war as gloss aircraft finishes.

During the development of aircraft camouflage in the mid-1930s, standards for the various camouflage and identification colours were produced in small numbers by the RAE. These took the form of brushed out samples of dope on small pieces fabric and brushed out samples of paint on small pieces of aluminium.

The first attempt to reproduce colour standards for widespread use by the Aeronautical Inspection Directorate took the form of printed colour cards which were stuck inside a small booklet. These were manufactured for the Air Ministry by the Mitchell Colour Card Company and delivered in February 1939. During 1939 Sky Blue and Special Night were added to the Air Ministry’s list of camouflage colours, followed by Sky, Middle Stone and Azure Blue in 1940.

When the Ministry of Aircraft Production (MAP) was formed in 1940, it took over the responsibility for producing colour standards for aircraft paints from the Air Ministry. The MAP standards had the form of samples of paint applied to cards which were bound into small booklets. When the MAP was absorbed into the Ministry of Supply on 1st April 1946, the MoS took over the responsibility for aircraft colour standards. These took the form of painted sheets of card, each enclosed in an envelope which was then bound in a ring binder and entitled ‘Ministry of Supply Standard of Colour Gloss and Smoothness for Aircraft Supplementary to BSS 381’. Not until 1964 were aircraft colours included in BSS 381C. Any colours found in various editions of BSS 381 prior 1964 are there because they were already in BSS 381 (first issued in 1930) when they were chosen for an aircraft application, e.g., Middle Stone.


Aircraft Design Memorandum 332, Issue 2, dated 8th September 1939, listed five material specifications for top coat camouflage finishes on RAF aircraft. These were Air Ministry Directorate of Technical Development Material Specification DTD 308 Matt Cellulose Finishes and Primer, issued July 1936; DTD 314 Pigmented Oil Varnishes and Primer, issued September 1936; DTD 83A Aeroplane Doping Schemes December 1935; DTD 63A Cellulose Enamels and Primer (for metals and timber) April 1939; and DTD 260A Pigmented Oil Varnishes and Primer (for metals and timber) date of issue unknown but reprinted in August 1940. DTD 314 and DTD 260A were synthetic alternatives to DTD 308 and DTD63A respectively, developed in case of a shortage of nitro cellulose, which would presumably be needed for explosives manufacture (gun cotton) during wartime.

DTD 308/314 were introduced because of a need for matt finish paint for camouflage colours and “the resulting dry film from such an application should match the standard which was obtainable from the Director of Aeronautical Inspection in mattness, colour, and smoothness of finish”.

DTD 63A/260A, when dry should have a glossy finish. The colour of the material was to be one of the British Standard colours listed in the latest issue of BS Specification 381, or when an aluminium finish was required, the standard was obtainable from the Director of Aeronautical Inspection at the Air Ministry, and later the MAP. In March 1940, as this material specification was being applied to Blenheim bombers on the production line (Sky), the specification was amended in that the requirement that the finishing coat should dry having a glossy finish was deleted. Thereafter it seems to have been referred to as DTD 63 with reduced gloss’.



BoBF Hurricane LF363, undersides painted BSS 381 (1930) No 16 Eau de Nil not Sky. The man responsible explains.

“I worked out from the time date that LF363 was to be painted to represent that air ministry spec ‘Sky’ had not reached the squadron level and therefore the aircraft was most likely to be in Eau de Nil. There was a lot more research involved by me to be honest, and I obtained a period sample chip of Eau De Nil (1930) which is nothing like the colour in the current BS381c range. I couldn't use the sample to give to the paint company for matching as it was very fragile and had to be returned to its owner but I mixed 10 samples of BS381c range Sky with varying amounts of dark green added in 10cc shots from a syringe. I then sprayed them onto the primer coat chips we were using on the aircraft. Once dry I compared them to the original sample and then sent my chosen sample to the paint company who I am pleased to say matched it perfectly. I later compared the original chip from 60+ years ago to the completed aircraft and other than the glossier sheen on LF363 it was a perfect match.”

3/. The "evidence" for Sky Grey's (a R.N. colour) alleged use seems to be the discovery of grey tail wheel legs, during a couple of "digs." I'm not sure how generally aware people are, of this, but every Spitfire part was undercoated in a light, or medium, shade of grey; perhaps consideration should be given to the idea that the top colour, over the years, has come away, or even that, in the rush of 1940's service requirements, some items were fitted with only an undercoat, and not the benefit of a top coat (one ex-609 Squadron rigger told me,"After a repair, we just slapped on any colour, green, grey, sky-blue-pink, we didn't care, so long as we got them back up.")

An under surface colour matching Sky Grey has been identified on two Spitfires by researchers who are quite capable of telling the difference between it and grey undercoat. In addition there are two starboard elevators from unidentifiable aircraft in museums that have Sky Grey under surfaces. It is impossible to link these definitely to aircraft lost in 1940 but it is believed that they were.




Tailwheel and strut from Spitfire Mk I, X4325, held at Shoreham Aircraft museum. Colour matches Sky Grey.



Fabric covered elevator from unidentified aircraft held at Brenzett Aeronautical Museum. Sky Grey on the under surfaces. Where the Sky Grey paint has flaked off the original Aluminium (silver) finish is revealed.

4/. From pre-war Sky blue had been a standard colour for use on drones like the Queen Bee, so it's entirely logical that some airfields would have had stocks, and it's also possible that (since no-one had any idea what Sky was) some aircraft were mistakenly painted with it.

No it was not. Sky Blue was developed in 1939 by the RAE specifically for use on the undersides of Queen Bee (radio controlled Tiger Moth) drones but never used for its intended purpose. The air diagram has a hand written annotation that the colour should look as German as possible. At a meeting on 23rd July 1940, at the Air Ministry, to consider aircraft colourings and markings with a view to achieving the maximum degree of standardization it was decided, subject to agreement by the War Office, that pilotless target aircraft should be issued with duck egg blue (Sky Type S) under surfaces without roundels and that, if necessary, roundels could be painted on by the units themselves.

Sky Blue was one of the colours, along with Azure Blue and Light Mediterranean Blue sanctioned for use on the undersides of aircraft in the Mediterranean and Far East. Applied to the undersides of 151 Wing Hurricanes sent to Murmansk and used on RAF Flying Fortress Mk Is instead of Cosmic (PR Blue) which had been requested by Bomber Command. It is also the chief suspect for the “Light Blue” applied to the under surfaces of Blenheims belonging to the squadrons that were to replace the Fairey Battle Squadrons in France

There is anecdotal evidence and eye witness accounts of fighter aircraft having light blue undersides but it is not possible to say with any certainty what was meant by light blue. There is no reason why Sky Blue could not have been used, unlike the similar looking Azure Blue which had not been invented or named at the time of the BoB, but so far no physical evidence has been found that proves its use.

Following a meeting at the Air Ministry on 30th October to address fighter camouflage and markings, on 27th November day fighters were to have port wing painted Night (black) and spinners painted Sky and an 18 inch Sky band was to be painted around the rear fuselage. As units began to request supplies of paint to comply with the instructions, 3 MU Milton (where you got your paint from) signalled the RAE on 18th December to advise them that they had no Vocabulary of Stores reference number for Sky. The RAE was asked to inform 3 MU which shade of Sky, Blue or Grey was required. (i.e., was Sky, Sky Blue or Sky Grey?). They then stated they were issuing Sky Blue. As a result contemporary photographs of aircraft often show a marked contrast between the under surface and the spinners and fuselage band painted with Sky Blue.

After the war it fell from use and was not included in the MoS colour range.

There are two different colours mentioned by the author in the article, both named Sky Blue. As well as the Sky Blue on the Air Ministry list there was a Sky Blue in BSS 381. In order to distinguish Sky Blue from BSS 381 (1930) No 1 Sky Blue some authors now use the term Air Ministry or AM Sky Blue for Sky Blue. Much of what has been said of Eau de Nil can be applied to BSS 381 (1930) No 1 Sky Blue as well.

The under surface colours featured in the article are based on archaeological evidence gathered in the 1990s and published around the turn of this centaury.

It can be deduced from the repeated references to Sky Type S being used, when supplies become available, which appear in documents throughout June and July of 1940, that supplies of Sky to either DTD 63A reduced gloss, or DTD 83A, DTD 308 and DTD 314 Type S, were generally not available to fighter squadrons during those months.

Eyewitness accounts of the period June/August 1940, suggest that there were various shades of green, blue and grey being used of day Fighter under surfaces before Sky became the most commonly seen colour from late-August onwards.

Archaeological evidence suggests that what would appear to have happened is that, following Signal X915 of 6th June 1940, the fighter squadrons began to indent the stores organisation for supplies of Sky Type S. However as supplies of this colour and material were difficult, if not impossible to obtain they were forced to use something else instead. It might be reasonable to assume that when confronted with demands for a colour and material which was not available, the paint manufacturers would supply whatever was available.

British Standard Specification 381 ‘Schedule of Colours for Ready Mixed Paints’ was issued in November 1930 and still current in 1940 and available to DTD 63A. The standard appears to offer two colours which might possibly have been used, which would account for the subjective colloquial descriptions of the under surface colours reported by eyewitnesses at the time of ‘duck egg blue’, and ‘a rich duck egg green’. These colours were BSS 381 (1930) No 1 Sky Blue, a light blue-green colour which could be described as duck egg blue; and No 16 Eau de Nil which could be considered to be a duck egg green. That these two colours were used in place of Sky is supported by the available archaeological evidence, wreckage of aircraft lost during 1940 held in a number of museums in Kent and Sussex.

Matching the samples of paint still adhering to wreckage of several aircraft revealed that the ‘rich duck egg green’ had several minor variations in colour while all were consistently smooth and slightly glossy, while only one shade of blue which was also smooth and slightly glossy , appears to have been used. Comparison with various colour standards revealed that all the minor variations in the ‘rich duck egg green’ were near matches for BSS 381 (1930) No 16 Eau de Nil; while the ‘duck egg blue’ was a match for BSS 381 (1930) No 1 Sky Blue. When the dates the aircraft were lost is set down in chronological order a pattern suggests itself.

Aircraft Date Lost Under Surface Colour
Hurricane, P3479, 56Sqn 13 August Sky
Hurricane, V6581, 85 Sqn 31 August BSS 381 (1930) No1 Sky Blue
Hurricane, P2946, 253 Sqn 2 September Sky
Hurricane, P3310, 73 Sqn 5 September ‘Eau de Nil’
Hurricane R4230, 249 Sqn 7 September ‘Eau de Nil’
Spitfire, P9467, 603 Sqn 7 September Sky Grey
Hurricane, P2728, 607 Sqn 7 September ‘Blue Grey’
Spitfire, X4325, 41Sqn 11 September Sky Grey
Spitfire, R6625 14 September Sky
Hurricane, V7357 17 September Sky
Spitfire, X4410 20 September Sky
Spitfire, X4422, 92 Sqn 27 September Sky
Spitfire, P9469, 222 Sqn 7 October ‘Eau de Nil and BSS 381 (1930)
No.1 Sky Blue
Hurricane, V6722, 501 Sqn 8 October Sky
Hurricane, L1928, 253 Sqn 10 October Sky
Spitfire, P7303, 616 Sqn 27 October Sky
Hurricane, V6879, 605 Sqn 1 November Sky
Blenheim, T2161, 82 Sqn 4 December ‘Eau de Nil’

Sky only becomes common from mid-September onwards with substitute colours by far the most common until then. While such a small sample cannot be regarded as conclusive, it does appear to reflect the picture obtained from the documents consulted and eyewitness accounts.

The paints used instead of Sky therefore appear to be of three colours. The first is Sky Grey which was surprisingly common given that there is little if any mention of it being used on RAF aircraft at this time in published literature. Besides the aircraft known to have carried Sky Grey listed above it has also found on the remains of two separate but unidentifiable aircrafts’ remains.

The second colour has been described as ‘Eau de Nil’ in the above list’. Examination of the wreckage revealed that there were several slightly different shades of the Eau de Nil colour. These range for an exact match for BSS 381 (1930) No 16 Eau de Nil, to FS 595B 14533 and 14449. These are not widely differing colours; the difference is so slight that samples of each colour have to be compared next to each other in order to perceive a difference. This slight difference may be due to supplies of paint being obtained from different manufacturers, or being from different batches of paint from the same manufacturer. In all cases the surface finish was smooth and quite glossy indicative of materials supplied to DTD 63A with reduced gloss.

One specific example where Eau de Nil has been used where Sky was called for was Spitfire P9469 of 222 Squadron coded ZD*T that was lost on 7th October 1940, the remains held by the Robertsbridge Aviation Society.

While there is not trace of the Night and White scheme on the wreckage, it was found to have three layers of paint. The first layer of paint next to the metal appeared on the surface to be an unidentified brown colour. However, when a loose flake of the paint was removed by one of the Society’s members, the side that had been next to metal was found to be an exact match for BSS 381 (1930) No 16 Eau de Nil.

The second layer of paint was a green colour matched to FS 14449. It had a very smooth finish, which while not a full gloss, had some degree of shine. This might be indicative of DTD 63A with reduced gloss.

The top layer of paint matched BSS 381 (1930) No 1 Sky Blue. This is a pale blue with a hint of green which could colloquially be described as ‘duck egg blue’. This was also found to be smooth and shiny indicative of DTD 63A with reduced gloss.

Thus it would appear that P9469 was repainted in service hands at least three times during the summer of 1940 without actually having carrying the right colour.

Hurricane, P2728 was painted with a blue-grey colour that has not been matched any of the known standards. The closest FB 595 match is 35414 but is too dark and too green.

If the RAF could not get supplies of Sky Type S, it would seem the aircraft manufacturers were little better off. While eyewitness accounts suggest that Blenheims built by Bristol in the early part of 1940 were finished Sky, albeit to DTD 63A with reduced gloss, archaeological evidence shows that the colour that was applied to Blenheim under surfaces on the production line at Rootes was not.

The evidence is provided by the remains of Blenheim Mk IV, T2161 of 82 Squadron held by Brenzett Aviation Museum. This particular was built by Rootes and first delivered to the RAF on 10th August 1940, at a time when according to the accepted view; Sky was well established both on the production line and in service. The paint that remains on the wreckage is however, quite unlike the correct shade of Sky, being an excellent match for FS 595B 14533. This is a near match for BSS 381 (1930) Eau de Nil. Once again the finish is very smooth and glossy indicative of materials to DTD 63A with reduced gloss.

In some cases, individual units mixed their own paint but so far no official documentation has been found on this subject. The Service was advised not to mix materials to DTD 308 with those of DTD 314 to this end. Some idea of the confusion caused by the introduction of Sky Type S is found in the correspondence of Wg Cdr WEB Hurst, then a 22-year-old corporal. He wrote to his wife from his posting in Gloucestershire in August 1940:

"We had to paint some of our kites and for some obscure reason we had to paint them duck egg blue. Why they should choose duck egg blue I can't imagine but ours is not to reason why, so duck egg blue they had to be.

Well, to start with we couldn't get any duck egg blue paint, nobody seemed to have heard of it, so the only thing to do was to mix some. The first thing we had to decide was 'what colour is duck egg blue?'

Nobody knew. Nobody could even remember having seen a duck's egg in the raw, so we were stumped again. Funnily enough nobody but me thought of trying to get hold of a duck's egg from somewhere but somehow my suggestion, that someone should be sent to try and procure one, wasn't received very favourably.

Then we found somebody who remembered having to mix some before. Oh it was a long time ago but he definitely remembered having to mix blue and white paint to the ratio 15:6. Oh good. But was it 15 parts of blue or 15 parts of white? He wasn't sure but thought it was blue. The only thing to do was to try it out and see what it looked like. Well, I should like to see the duck that could lay a beautiful Oxford blue egg! We concluded it must be the other way about, so we mixed a lot more white with it and eventually got about five gallons of a sort of Cambridge blue, which we all agreed a duck's egg might possibly look like! We slapped this on and as it didn't look too bad we left it to dry and went to dinner. When we got back something seemed to have gone wrong for our duck egg blue had dried a beautiful violet! Now this was rather disheartening but it was quite funny to see the Flight Sergeant tearing his hair when he saw it, so we asked him to have a go. He suggested putting more white and some yellow with our mixture. We followed his suggestion and the resulting mixture didn't look too bad, though a bit greenish, but a duck might possibly have been able to produce an egg to match it, so we slapped that over the top of the violet. I don't think it will look too bad when dry but we shan't know the final result until we see it tomorrow. I don't think anyone will dare to open the hangar door in the morning."

In a letter two days later, he said:

"We finished duck egg blueing our planes by the way. That first one dried alright and as we had used all the paint on it we had to mix some more and get the right shade. Most of them are a bluey greeney shade, but some of them vary from an almost pea green to almost sky blue!"


BSS 381 (1930) No 1 Sky Blue. Known colloquially as duck egg blue which is a good description of its aquamarine hue. The closest FS 595B match is 14325. The current No 101 Sky Blue is a little darker than the No1 Sky Blue in the 1930 edition. (The numbering system was altered in the 1948 edition.) Available from White Ensign Miniatures (WEM) in their Color Coats range.

BSS 381 (1930) No 16 Eau de Nil). Known colloquially as duck egg green. Its grey/green hue may be described as a rich duck egg green. The closest FS 595B match is 14533. Available from White Ensign Miniatures (WEM) in their Color Coats range.




Colour matching on P9469. The colour is described as a rich duck egg green and was an excellent match for FS 595B 14449.



Colour matching on the tailwheel strut of P9469. In this instance the colour was a duck egg blue that matched BSS 381 No1 Sky Blue.



P9469. Here both the duck egg green and duck egg blue colours and be seen. Both finishes were smooth and quite glossy. The green had been applied first and later overpainted with the blue.

It's very easy to quote others' research, but it does pay to go to available sources, and read what they contain.
27-1-39, Supermarine were told to paint the undersides of the wings only (not the whole aircraft) black and white, divided by the centre line of the aircraft, which would have left the remainder still in its original silver. This followed a meeting of the Modifications Committee 25-1-39; the only debatable point was the painting of ailerons, and asked for the Resident Technical Officer's views as to whether that work could be entrusted to Service personnel. That order was never rescinded, so the scheme was not "reintroduced," but was always in place (Supermarine always introduced any colour changes as a modification to the production line, for example mod 125, 30-11-39, standardised the roundels, and deleted the serial nos from under the wings.) If some aircraft were painted entirely black & white underneath, it was simply due to a misreading of the instructions.
If Sky Blue was never used, how is it that Farnborough's director, 18-7-41, said, "Sky Blue has been in use for over 3 years on target aircraft, and is very similar to the colour used on German aircraft." There are also recorded complaints that some AA gunners had difficulty picking it out, against the blue sky, so units were told to use their own discretion as to whether they added roundels, to aid less experienced personnel.
Talk of "the grey primer" is somewhat spurious, since there were, at least, three, known mainly by the somewhat enigmatic U.P.1, U.P.2, and U.P.3, so pedantically saying that researchers could easily tell the difference is a slight over-simplification.
The fact remains that British Standards made no direct input into Air Ministry colours, throughout the war; that some have "matched" 60-year-old colour samples to a B.S. colour is pure luck, nothing more. There's always the possibility that some units got hold of paint from local suppliers, or still had some pre-war stocks, but it was never an official policy to use the B.S. If you check records, Eau-de-Nil was no. 16, in the B.S. list, but Sky was 9A, with Sky Grey 9 (more opportunities for confusion) in the Air Ministry lists. Even the much-respected Ian Huntley was caught out by the "Eau-de-Nil" misnomer, saying that it was a match for Sky, when it actually was in the 1930 B.S. list, some 8/9 years before Cotton invented Camotint/Sky.
Edgar