Humbrol 90 Beige Green is a better match for Sky than H23 Duck Egg Blue.
The first description of Camotint/Sky was ‘a light sea green colour’ and it was first called Duck Egg Green (their capitals not mine) in a RAE report in November 1939. The RAE gave it the name Sky in January 1940. It is normal to find it described as duck egg green in documentation and correspondence in the first half of 1940. Duck-egg bluish green first appears in a signal sent by the Air Ministry 7th June 1940 which said that “the colour of Sky Type S, repeat S, may be described as Duck Egg Bluish Green”. DTD Technical Circular No 75 issued on 25th July stated fighters were to be “Painted duck egg bluish green (Sky Type S).”
By July 1939 there was some concern in Bomber Command about the under surface colouring of its aircraft. The Night under surfaces was felt to make them conspicuous by day against a sky background, and it was by day that most of the flying over enemy territory was envisaged as being carried out. All bombers not definitely allocated to night operations should be painted a colour, or combination of colours, that would make them as inconspicuous as possible against various forms of sky background. If any of these aircraft were required for operations by night, it was thought the under surfaces could easily be blacked over with a temporary matt finish. It was also thought a suitable under surface colour might be silver, light blue, or grey, or some other colour or combination of colours. Despite the unease in Bomber Command no further work was done on under surface camouflage schemes until the outbreak of war in September 1939 brought the activities of Sidney Cotton and the PDU at Heston to the attention of higher authorities.
The PDU had been set up as a result of a meeting at the Air Ministry (AM) on 22nd March 1939, where it was decided to form an experimental unit for the purpose of testing, and if successful, developing novel techniques for photo reconnaissance sorties over enemy territory. The basis of the scheme was the use of high speed and invisibility and the originator of the scheme, Sidney Cotton was put in charge.
The unit’s first equipment was the Bristol Blenheim which was found to be too slow, and with Night under surfaces, too visible from below. A determined effort was made to clean-up the airframe as much as possible and a different, lighter colour was applied to the under surfaces.
Prior to the war, Sidney Cotton had been carrying out clandestine photography while engaged on what were ostensibly legitimate flights over Germany on behalf of the SIS. The aircraft he used was painted a ‘very pale green’ which did not look out of place on a civilian aircraft but happened to be very good at concealing it from observers on the ground. It appears this ‘very pale green colour’ was applied to the under surfaces of the Blenheims at Heston.
Bomber Command evidently heard something of the PDU’s modifications to their Blenheims as, during October, a Blenheim from 139 Squadron was sent to Heston to be modified in a similar manner to those of the PDU. As part of these modifications the Blenheim received the glossy camouflage paints then in use by the PDU, consisting of Dark Earth and Dark Green applied in the usual disruptive pattern on the upper surfaces and what was described as a ‘light sea green’ colour on the under surfaces. This new camouflage must have been reported in some detail to the AM as, during early November, the AM expressed a wish that representatives of the RAE pay a visit to the PDU and give their opinion as to the advantages and disadvantages of the PDU’s camouflage scheme. This resulted in two representatives from the RAE visiting Heston on 18th November 1939.
They found a Blenheim Mk IV had been extensively worked on to eliminate gaps in the skin joints and had been given a very smooth, glossy paint finish with the usual Dark Green and Dark Earth disruptive pattern on the upper surfaces and a colour described in the RAE report as “Duck Egg Green termed Camotint” on its under surfaces. It was claimed that this “Duck Egg Green” finish rendered the aircraft practically invisible at heights of 10,000 ft.
While it had been found that the new smooth finish helped to improve the performance of the Blenheim, it was realised that the glossiness would compromise the camouflage effect. It was therefore requested that the RAE supply Heston with a suitable paint that would match Dark Earth, Dark Green, and Duck Egg Green in colour and would be smoother than the standard camouflage finishes but without the glossiness the dopes currently being used. This request would result in the introduction of Type S finishes.
Bomber Command was most impressed with its streamlined Blenheim on 139 Squadron as, on 25th November 1939, HQ Bomber Command wrote to both the AM and HQ Fighter Command, to inform them that experiments had been carried out at Watton on 139 Squadron Blenheims to clean-up the aircraft with a view to increasing their speed. The experiments were judged to have been a success and it was intended to continue the work on other Blenheim squadrons in the Command.
The letter then stated that coincident with this process a change had been made to the under surface colour of these Blenheims which were now painted what was described as ‘Grey-Blue’ so as to merge into the background of the sky when viewed from below. Bomber Command wished that this change of colouring be brought to the attention of all concerned as the change ws being progressively introduced into Blenheim bomber squadrons; and it would also be necessary to inform the French authorities as these two squadrons of repainted Blenheims were to replace two Fairey Battle squadrons in France in the very near future.
On 29th November 1939 signals A399 and A432 informed No 1 Mission for onward transmission to the French, and all home based forces, that a ‘Light Blue’ colour was being introduced for the under surfaces of Blenheim bombers instead of the present black finish. The AM informed Bomber Command that this had been done in a letter dated 2nd December. The AM approved of the change in colouring and stated that red, white and blue roundels were to be carried on the under surfaces of the wings of aircraft painted in the ‘blue-grey’ colour.
It is not clear exactly what this colour, described in the official correspondence as ‘blue-grey’ and ‘light blue’, actually was. Available photographic evidence suggests that it was much lighter than Medium Sea Grey. Most likely it was Air Ministry Sky Blue. However, there may have been a blue grey colour in use about this time. A ‘Light Blue-Grey’ colour was found on the remains of Hurricane P2728 at Hawkinge which has not been matched to any known standards.
By mid-December, the AM was trying to get such improvements as it could incorporated into Blenheims on the production line. There were, however, problems with the camouflage finish. On 10th January 1940 a meeting was held at the AM to try to get to grips with the problems of introducing two new under surface camouflage materials, one of which ws Camotint.
The first problem was the means by which Camotint was obtained. Heston obtained its materials directly from the manufacturer Titanine. When Bomber Command began submitting demands for this material to the AM for use on its day flying Blenheims, nothing was known about it by the Directorate of Engineering. Not being able to obtain supplies of it may have been the reason why Bomber Command used a light blue colour instead.
It was suggested that a technical leaflet might be published giving full instructions regarding the various materials used to obtain the new finish, together with the method of their application, and an AMO (Air Ministry Order) be issued introducing the items for use on all Blenheims. In this connection it was stated that the question of re-painting Blenheim Fighter squadrons was under consideration.
The overriding concern was one of provisioning the new colour. The initial problem was that it needed to be determined exactly what quantities of this new material were required for maintenance purposes on aircraft that were already finished in Camotint, and for re-painting Blenheims held by the ASUs (Aircraft Storage Units) awaiting issue. In the longer term, should the new finish be approved for general use, some estimate of the amount required was needed. At that time samples of Camotint were being prepared by Cellon as an alternative supply to Titanine, but no difficulties were envisaged in obtaining supplies of the new materials from any of the approved paint manufactures.
While this had been going on, work had been put in hand at the RAE to produce a finish employing a very finely ground pigment which it was hoped would give a smooth matt finish. On 25th January 1940, the RAE despatched to Heston, 5 gallons of Dark Earth Type S, 5 gallons of Dark Green Type S, and 20 gallons of Sky Type S. Sky was the name given by the RAE to the ‘duck egg green’ colour known at Heston as Camotint. The suffix Type S was the name given by the RAE to the smooth paint that featured a more finely ground pigment which resulted in a smaller particle size and so smoother finish.
So, by the end of January 1940, the only Sky Type S available was at in the hands of the PDU at Heston, having been supplied in small quantities by the RAE. In February Bristols have appeared to have modified the camouflage scheme of the Blenheims they were producing to have what has been described as ‘light green’ under surfaces. This is understood to have been the first use of Sky on a production aircraft, but this was almost certainly not the new Type S standard; more likely being the same material that Titanine had been supplying to the PDU, a gloss finish to DTD 63A. An eyewitness account suggests that Blenheims built by Bristol at Filton during the early part of 1940, were finished the correct colour Sky, even though the materials used were probably not Type S.
Supporting evidence for this is a letter dated 20th April 1940, sent by the AM to Bristol headed “Camotint – Specification for”. In it, Bristols were told that, “It is agreed that you should call on the schedule for Mod 864 on the Belheim Mk IV for Lacquer to DTD 63 with reduced gloss. The gloss is not to exceed that shown on samples obtained from the Bristol Aeroplane Co Ltd. This degree of gloss is to be permitted on the Blenheim IV only, all other aircraft will comply with the new ‘Type S’ standard. You will arrange with Rootes to supply samples finished with the above DTD 63 with reduced gloss. As regards colour, the pale blue-green which has been called Camotint is now defined as Standard Sky this description should be given in your schedule”.
DTD 63A was then an aircraft finish specification listed in Aircraft Design Memorandum 332, ‘External Finish on Aircraft (issue 2)’dated 8th September 1939. DTD 63A was a Material Specification for Cellulose Enamels and Primers for use on metal or wood which was apparently available in a whole range of colours , including those of the Air Ministry – for example Dark Earth and Dark Green. It was to be suitable for application by brush or spray and originally was to dry to a uniformly smooth covering having a glossy finish. In an amendment dated March 1940, the requirement to dry to a glossy finish was dropped, presumably leading to the finish that the AM referred to as ‘DTD 63A with reduced gloss’ from April onwards.
If the supply situation was difficult with ‘Sky to DTD 63A with reduced gloss’ being applied to one aircraft type, it became infinitely worse from early June when the use of Sky on Fighter Command aircraft was authorised. On 6th June the AM sent Signal X915 which stated that all under surfaces of fighter aircraft (that is mainplanes, fuselage, and tailplanes), were to be doped to Sky Type S. All roundels on the undersides of mainplanes were to be removed. All previous instructions regarding painting and marking on under surfaces of fighter aircraft were cancelled.
This immediately caused problems as the fighter squadrons had no idea what colour Sky Type S was. The AM tried to get around this problem by sending a signal to all concerned on 7th June which said that “the colour of Sky Type S, repeat S, may be described as Duck Egg Bluish Green”. This seems to be the earliest use of any variation of the term ‘Duck Egg Blue (Sky Type S)’ and it would seem that whoever wrote the original signal did not really know whether the colour he was describing was a blue or a green. From this point onwards Duck Egg Blue or Duck Egg Bluish Green are the names used in documentation and so they passed into common usage.
AMO. A.926 – Aircraft Colouring and Recognition Markings was issued on 12th December 1940. In this AMO the under surfaces of operational aircraft were to be either matt black or duck egg blue (Sky Type S). The issue of this AMO caused some upset at the RAE as on 21st December a letter was sent to the Air Ministry in which the RAE took issue with several of the points covered in the AMO. Amongst these points were the terms used to describe the under surface colours, i.e., ‘duck egg blue Sky Type S’ and ‘matt black’. The RAE was of the opinion that the term ‘duck egg blue’ should not be used as in the RAE pattern book the colour used for this purpose was called ‘Sky’, the term ‘Sky Type S’ should be just ‘Sky’ as all colours were now of Type S; and the use of the term ‘matt black’ did not make clear whether ‘Night’ or ‘Special Night’ were being referred to. When AMO A.926 was amended in January 1941 the references to matt black were changed but ‘duck egg blue (Sky Type S)’ was still there. When DTD Technical Circular No 144 was issued in March 1941 was no mention of ‘duck egg blue’ or ‘Sky Type S’, only Sky. However the colloquialism ‘duck egg blue’ persisted in the minds of people and came to be associated with Sky.
