Spitfire XIV: Gloss, matte or somewhere in the middle?
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Airframes
Benevolens Magister
The Spitfire MkXIV in WW2 was painted in matt paints which had a very slight sheen, but not as 'smooth' as semi-matt. See the photo of your aircraft which I posted in your request for the style of the serial number presentation.
A call to an organisation such as The Fighter Collection at Duxford, should ellicit information on the paint types and suppliers, as this organisation, and other 'warbird' operators in the UK now tend to use authentic finishes, but which are more durable and stain-resistant, compared to the paints of WW2.
A call to an organisation such as The Fighter Collection at Duxford, should ellicit information on the paint types and suppliers, as this organisation, and other 'warbird' operators in the UK now tend to use authentic finishes, but which are more durable and stain-resistant, compared to the paints of WW2.
Materials for camouflage on metal or wood parts were matt cellulose finishes and primer to Specification DTD 308 or matt pigmented oil varnishes and primer to Specification DTD 314.
For glossy finishes on metal or wood (originally glossy finishes were required on external surfaces of target towing aircraft, and on the yellow areas of training and target aircraft.) either cellulose enamels and primer to DTD 63A or pigmented oil varnishes and primer to Specification DTD 260A.
For fabric parts doping scheme to Specification DTD 83A. When a glossy finish was required a final coat of transparent varnish was to be applied.
From the introduction of camouflage paints in 1937 there had been a debate about the effect of aerodynamic smoothness of the matt finish particularly to the Fairey Battle having its performance impaired by the application of the camouflage paint. Investigation by the RAE revealed that the rough surface obtained on the Battle was not due to the paint itself, but by its 'inept application' by the manufacturer in less than ideal circumstances. Once the findings became known the debate seems to have died down for a while.
Early in 1940 the debate reopened, it seems, in response to Sidney Cotton's inclusion of a smooth gloss finish in the cleaning-up process carried out on a PDU Blenheim. Two representatives from the RAE had travelled to Heston on the 18th November 1939 to give the Air Ministry their opinion as to the advantages and disadvantages of the PDU's camouflage scheme.
While it had been found that the smooth finish had helped to improve the performance of the Blenheim it was realised that the glossiness would compromise the camouflage effect. The RAE was asked to supply Heston with a suitable paint that was smoother than the standard camouflage finishes but without the glossiness of the dopes currently being used.
Even while the RAE was in the process of producing the initial quantity of smooth camouflage paint for the PDU, moves began to be made to try and improve the surface finish of Service aircraft. On 9th January 1940 a note was produced at Farnborough entitled 'Possible methods of obtaining smoother finish on Production Aircraft'. The note opened by stating that the cleaning-up, that was put in hand on numerous types of aircraft on the production line, called for a surface smoothness on certain parts of the aircraft such that the roughness height did not exceed one half of one thousandth of an inch.
There were considered to be three alternatives open to the aircraft manufactures to achieve this.
First. They could use different paint materials that were easier to apply on not liable to dry with excessive roughness due to unskilled spraying, especially where colours overlapped.
Second. The existing paint materials and methods of application could be retained, and the final finish could be rubbed down by lightly applying Wet and Dry paper used wet.
Third. The existing paints and materials could be retained but the method of application greatly revised by careful control over the humidity and temperature of the paint shops; avoiding drafts and air movements in the paint shops; avoiding dust on the floors and in the air; ensuring more careful use of the spraying equipment to avoid partially dry or dry spray particles; abolishing the merging of adjacent colours at the pattern outlines; preparing a smooth undercoat by rubbing down with abrasives before application of the finishing coat; and finally avoiding long storage of the paint before it was used.
The third alternative was considered to be a non-starter as it might involve serious changes in the layout of dope rooms and prove impractical. There therefore remained the first and second options and the choice of which one to adopt would appear to lie with the aircraft manufacturers. Both paint and aircraft manufacturers would shortly receive samples of the finish now required acceptable fro the point of view of gloss.
Work had been put in hand at the RAE to produce a finish employing a very finely ground pigment which ws hoped would give a smooth matt finish. On 25th January 1940 five gallons of Dark Earth Type S, five gallons of Dark Green Type S, and 20 gallons of Sky Type S were despatched from the RAE to Heston. Sky was the name given by the RAE to the 'duck egg green' colour known at Heston as Camotint. Type S was the name given by the RAE to the new smooth paint that featured a more finely ground pigment that resulting ion a smaller particle size and thus a smoother finish.
Over the next few months representatives from the RAE visited a number of aircraft manufacturers to inspect the current standards of finish. Methods of improving the finish were discussed with the manufacturers, but the suggested method of rubbing down the final coat with Wet and Dry paper was considered to involve a large increase in the time necessary to camouflage an aircraft.
On 15th March 1940 a meeting was held to review the present position relating to the introduction of 'Smooth Paint Finish on Aircraft' and to consider the effect this change would have on production, maintenance, aircraft speed and camouflage.
It was thought that production would be adversely affected if the process time for painting were increased. The application of the new Type S paint was exactly the same as the existing matt paints. Unless strict precautions were observed in the paint room, particularly in the avoidance of dust, it was preferable to rub down the undercoat before applying the Type S finish. A similar result could be obtained by a final rubbing down of the existing matt paint. Experiments had been made by rubbing down a Spitfire wing which showed it might take as long as 10 man hours to rub down the whole machine when washing and drying time were taken into account. Such an increase in time would necessitate and increase in floor space and the provision of the facilities which might not be practicable in some factories. It was also felt that the class of labour which would be employed on this work could not be relied on to avoid rubbing all the paint of protuberances such as rivet heads. It was stated that without rubbing down or special precautions better results would be expected by using the new Type S paint. Improvement was possible by avoiding excessive roughness at the merging of the colours on the boundaries of the camouflage colours. It was agreed that this could be brought about by using masks to get a hard edge to the camouflage pattern and making the gradual merging of colours no longer obligatory.
The meeting agreed that the new Type S paint could be adopted to advantage without affecting production and it would be left to individual aircraft manufacturers to produce the desired smoothness, either by taking greater care in spraying or rubbing down the final finish. It was agreed that it would be impracticable to impose rigid inspection methods. It was suggested that a large panel showing the required finish could be displayed in the paint room.
No effect on maintenance was foreseen. It was thought that it might be necessary for the Service and contractors involved in the assembly process to avoid damaging the finished surface.
For glossy finishes on metal or wood (originally glossy finishes were required on external surfaces of target towing aircraft, and on the yellow areas of training and target aircraft.) either cellulose enamels and primer to DTD 63A or pigmented oil varnishes and primer to Specification DTD 260A.
For fabric parts doping scheme to Specification DTD 83A. When a glossy finish was required a final coat of transparent varnish was to be applied.
From the introduction of camouflage paints in 1937 there had been a debate about the effect of aerodynamic smoothness of the matt finish particularly to the Fairey Battle having its performance impaired by the application of the camouflage paint. Investigation by the RAE revealed that the rough surface obtained on the Battle was not due to the paint itself, but by its 'inept application' by the manufacturer in less than ideal circumstances. Once the findings became known the debate seems to have died down for a while.
Early in 1940 the debate reopened, it seems, in response to Sidney Cotton's inclusion of a smooth gloss finish in the cleaning-up process carried out on a PDU Blenheim. Two representatives from the RAE had travelled to Heston on the 18th November 1939 to give the Air Ministry their opinion as to the advantages and disadvantages of the PDU's camouflage scheme.
While it had been found that the smooth finish had helped to improve the performance of the Blenheim it was realised that the glossiness would compromise the camouflage effect. The RAE was asked to supply Heston with a suitable paint that was smoother than the standard camouflage finishes but without the glossiness of the dopes currently being used.
Even while the RAE was in the process of producing the initial quantity of smooth camouflage paint for the PDU, moves began to be made to try and improve the surface finish of Service aircraft. On 9th January 1940 a note was produced at Farnborough entitled 'Possible methods of obtaining smoother finish on Production Aircraft'. The note opened by stating that the cleaning-up, that was put in hand on numerous types of aircraft on the production line, called for a surface smoothness on certain parts of the aircraft such that the roughness height did not exceed one half of one thousandth of an inch.
There were considered to be three alternatives open to the aircraft manufactures to achieve this.
First. They could use different paint materials that were easier to apply on not liable to dry with excessive roughness due to unskilled spraying, especially where colours overlapped.
Second. The existing paint materials and methods of application could be retained, and the final finish could be rubbed down by lightly applying Wet and Dry paper used wet.
Third. The existing paints and materials could be retained but the method of application greatly revised by careful control over the humidity and temperature of the paint shops; avoiding drafts and air movements in the paint shops; avoiding dust on the floors and in the air; ensuring more careful use of the spraying equipment to avoid partially dry or dry spray particles; abolishing the merging of adjacent colours at the pattern outlines; preparing a smooth undercoat by rubbing down with abrasives before application of the finishing coat; and finally avoiding long storage of the paint before it was used.
The third alternative was considered to be a non-starter as it might involve serious changes in the layout of dope rooms and prove impractical. There therefore remained the first and second options and the choice of which one to adopt would appear to lie with the aircraft manufacturers. Both paint and aircraft manufacturers would shortly receive samples of the finish now required acceptable fro the point of view of gloss.
Work had been put in hand at the RAE to produce a finish employing a very finely ground pigment which ws hoped would give a smooth matt finish. On 25th January 1940 five gallons of Dark Earth Type S, five gallons of Dark Green Type S, and 20 gallons of Sky Type S were despatched from the RAE to Heston. Sky was the name given by the RAE to the 'duck egg green' colour known at Heston as Camotint. Type S was the name given by the RAE to the new smooth paint that featured a more finely ground pigment that resulting ion a smaller particle size and thus a smoother finish.
Over the next few months representatives from the RAE visited a number of aircraft manufacturers to inspect the current standards of finish. Methods of improving the finish were discussed with the manufacturers, but the suggested method of rubbing down the final coat with Wet and Dry paper was considered to involve a large increase in the time necessary to camouflage an aircraft.
On 15th March 1940 a meeting was held to review the present position relating to the introduction of 'Smooth Paint Finish on Aircraft' and to consider the effect this change would have on production, maintenance, aircraft speed and camouflage.
It was thought that production would be adversely affected if the process time for painting were increased. The application of the new Type S paint was exactly the same as the existing matt paints. Unless strict precautions were observed in the paint room, particularly in the avoidance of dust, it was preferable to rub down the undercoat before applying the Type S finish. A similar result could be obtained by a final rubbing down of the existing matt paint. Experiments had been made by rubbing down a Spitfire wing which showed it might take as long as 10 man hours to rub down the whole machine when washing and drying time were taken into account. Such an increase in time would necessitate and increase in floor space and the provision of the facilities which might not be practicable in some factories. It was also felt that the class of labour which would be employed on this work could not be relied on to avoid rubbing all the paint of protuberances such as rivet heads. It was stated that without rubbing down or special precautions better results would be expected by using the new Type S paint. Improvement was possible by avoiding excessive roughness at the merging of the colours on the boundaries of the camouflage colours. It was agreed that this could be brought about by using masks to get a hard edge to the camouflage pattern and making the gradual merging of colours no longer obligatory.
The meeting agreed that the new Type S paint could be adopted to advantage without affecting production and it would be left to individual aircraft manufacturers to produce the desired smoothness, either by taking greater care in spraying or rubbing down the final finish. It was agreed that it would be impracticable to impose rigid inspection methods. It was suggested that a large panel showing the required finish could be displayed in the paint room.
No effect on maintenance was foreseen. It was thought that it might be necessary for the Service and contractors involved in the assembly process to avoid damaging the finished surface.
Continued
It was stated that an improvement in the speed of a Blenheim of between 2 -5 mph was to be expected from using a smoother surface finish and approximately the same result was obtained on the Hampden. It was felt that the increase in speed was well worth striving for.
It was stated that the surface obtained with the new Type S paint had a greater reflecting power than the matt surface then in use. It was difficult to access the reflecting power precisely in terms of increased visibility in the air or on the ground. It was agreed by the meeting that the improvement in speed appeared to justify this slight reduction in camouflage effect, but this was a matter for the Air Staff to decide. The meeting was of the opinion that such types as the Anson and Battle should not have any special effort made to improve the surface finish.
Retrospective action on aircraft already in service was not contemplated and the change to Type S finish would be introduced on the production line as soon as possible if the recommendations of the meeting were accepted by the Air Staff. Existing stocks of paint would be used up first.
The meeting made the following recommendations to Air Staff.
Type S paint for camouflage finish was to be introduced as soon as possible, subject to the Air Staff's acceptance of the departure from the matt finish then in use.
No retrospective action on aircraft already in service was to taken and existing stocks of paint were to be used up first.
Aircraft manufacturers were to be asked to improve the surface finish as much as possible, taking the new standard as showing the maximum amount of gloss allowable. The maximum roughness of one thousandths of an inch was to be aimed at. Rigid inspectional control would not be possible so the local technical committees were to explain to firms the need for this finish and encourage them to achieve the required results.
No change in the specification of the paint was thought necessary. The existing new paint was specified to the existing Specification Number (Type S). New standards were to be issued by the RAE to the paint and aircraft manufacturers.
The recommendations were approved and in late April a circular was sent to all RTOs entitled 'Improving Surface Finish on Production Aircraft; Adoption of Type S paints'.
The letter opened by reminding RTOs that their attention had already been drawn to the necessity of producing a smooth finish on production aircraft, something in the order of less than one thousandth of an inch, but it should be noted that the final roughness on many aircraft types was often as high as five thousandths of an inch and sometimes up to ten thousandths of an inch.. RTOs were informed that in order to assist still further towards achieving the desired result, it had now been agreed that the camouflage paints themselves were to be altered so that they were easier to apply and not so liable to give a rough finish due to unskilled application. The change in the manufacture of the paints was one of finer grinding of the pigment, so reducing the pigment size. It was noted that this would not prevent the paints from still being liable to coagulate into lumps if they were not used while still fresh. No change would be made to the specification number, but the wods 'Type S' woul;d be added to the title.
New Standards, i.e., sample panels, would be issued to the aircraft firms by the RAE. These standards would show the maximum permissible gloss and indicate the degree of smoothness towards which the firm should strive. If firms were to experience any difficulty in producing finishes that met with the new standards they were to seek help immediately from their paint supplier. All firms involved in the manufacture of paints and dopes were fully aware of the new requirements. It was stressed that it was most important that the final gloss coat should not exceed that of the standards otherwise the efficiency of the camouflage would be reduced. To assist in avoiding dry or partially dry spraying at the colour boundaries it had now been agreed that colour merging need not be done. Instead masks could be used for the different colours and the resultant sharp boundaries would be accepted. The new 'Standard of Finish' did not apply to the 'Special Night' black finish which was called for on the under surfaces of the fuselage and wings of Night Bomber aircraft.
As it was not felt practicable to apply a rigid inspection of the finish for either roughness or gloss at the aircraft manufacturing firms, roughness was to be estimated by feel after a little skill had been gained by using the Lycopodium grain comparison method. This was done by sprinkling the surface locally with a few Lycopodium spores and and then examining it through a Coddington Lens which had a magnification of approximately 20x. Lycopodium spores have a diameter of approximately one thousandth of an inch and by comparison with these, the size of any protuberances on the surface could be estimated. By comparison gloss was not considered difficult to assess by eye.
If the finish was to be rubbed down, the following method was to be used. A strip of Hydro Durexsil No 400A abrasive paper, 3 inches wide by 11 inches long, was to be folded around a pad of sponge rubber approximately three quarters of an inch thick, 2 inched wide and 4 inches long. The pad was then to be held between the thumb and forefingers so that about an inch of the 3 inch width projected beyond the fingers with the remainder of the pad lying in the palm of the hand. The surface to be rubbed down was then to be wetted with water and the pad applied as if it were a paintbrush using circular strokes with very light pressure. Care was to be taken not to touch rivet heads and to use the least possible pressure when passing over other projections. The surface should be kept wet, and a fresh area of the abrasive paper exposed at intervals as necessary. After rubbing down, the surface was to be thoroughly cleaned with water and a scrubbing brush before being left to dry.
Type S paintes might have been introduced gradually from circa May/June/July 1940 onwards, and at roughly the same time, the requirement for the colour demarcation between camouflage colours to be a soft one was made no longer mandatory. As a consequence there is no clear picture as to which manufacturer followed which process, and with which materials, and at what time. It is not easy to tell whether the original matt paint was used and then sanded down which would impart a slight sheen, or whether Type S materials were used.
By December 1940, with the exception of Special Night, all aircraft camouflage paints, including identification colours, whether synthetic or cellulous based were supposed to be manufactured using Type S materials.
It was stated that an improvement in the speed of a Blenheim of between 2 -5 mph was to be expected from using a smoother surface finish and approximately the same result was obtained on the Hampden. It was felt that the increase in speed was well worth striving for.
It was stated that the surface obtained with the new Type S paint had a greater reflecting power than the matt surface then in use. It was difficult to access the reflecting power precisely in terms of increased visibility in the air or on the ground. It was agreed by the meeting that the improvement in speed appeared to justify this slight reduction in camouflage effect, but this was a matter for the Air Staff to decide. The meeting was of the opinion that such types as the Anson and Battle should not have any special effort made to improve the surface finish.
Retrospective action on aircraft already in service was not contemplated and the change to Type S finish would be introduced on the production line as soon as possible if the recommendations of the meeting were accepted by the Air Staff. Existing stocks of paint would be used up first.
The meeting made the following recommendations to Air Staff.
Type S paint for camouflage finish was to be introduced as soon as possible, subject to the Air Staff's acceptance of the departure from the matt finish then in use.
No retrospective action on aircraft already in service was to taken and existing stocks of paint were to be used up first.
Aircraft manufacturers were to be asked to improve the surface finish as much as possible, taking the new standard as showing the maximum amount of gloss allowable. The maximum roughness of one thousandths of an inch was to be aimed at. Rigid inspectional control would not be possible so the local technical committees were to explain to firms the need for this finish and encourage them to achieve the required results.
No change in the specification of the paint was thought necessary. The existing new paint was specified to the existing Specification Number (Type S). New standards were to be issued by the RAE to the paint and aircraft manufacturers.
The recommendations were approved and in late April a circular was sent to all RTOs entitled 'Improving Surface Finish on Production Aircraft; Adoption of Type S paints'.
The letter opened by reminding RTOs that their attention had already been drawn to the necessity of producing a smooth finish on production aircraft, something in the order of less than one thousandth of an inch, but it should be noted that the final roughness on many aircraft types was often as high as five thousandths of an inch and sometimes up to ten thousandths of an inch.. RTOs were informed that in order to assist still further towards achieving the desired result, it had now been agreed that the camouflage paints themselves were to be altered so that they were easier to apply and not so liable to give a rough finish due to unskilled application. The change in the manufacture of the paints was one of finer grinding of the pigment, so reducing the pigment size. It was noted that this would not prevent the paints from still being liable to coagulate into lumps if they were not used while still fresh. No change would be made to the specification number, but the wods 'Type S' woul;d be added to the title.
New Standards, i.e., sample panels, would be issued to the aircraft firms by the RAE. These standards would show the maximum permissible gloss and indicate the degree of smoothness towards which the firm should strive. If firms were to experience any difficulty in producing finishes that met with the new standards they were to seek help immediately from their paint supplier. All firms involved in the manufacture of paints and dopes were fully aware of the new requirements. It was stressed that it was most important that the final gloss coat should not exceed that of the standards otherwise the efficiency of the camouflage would be reduced. To assist in avoiding dry or partially dry spraying at the colour boundaries it had now been agreed that colour merging need not be done. Instead masks could be used for the different colours and the resultant sharp boundaries would be accepted. The new 'Standard of Finish' did not apply to the 'Special Night' black finish which was called for on the under surfaces of the fuselage and wings of Night Bomber aircraft.
As it was not felt practicable to apply a rigid inspection of the finish for either roughness or gloss at the aircraft manufacturing firms, roughness was to be estimated by feel after a little skill had been gained by using the Lycopodium grain comparison method. This was done by sprinkling the surface locally with a few Lycopodium spores and and then examining it through a Coddington Lens which had a magnification of approximately 20x. Lycopodium spores have a diameter of approximately one thousandth of an inch and by comparison with these, the size of any protuberances on the surface could be estimated. By comparison gloss was not considered difficult to assess by eye.
If the finish was to be rubbed down, the following method was to be used. A strip of Hydro Durexsil No 400A abrasive paper, 3 inches wide by 11 inches long, was to be folded around a pad of sponge rubber approximately three quarters of an inch thick, 2 inched wide and 4 inches long. The pad was then to be held between the thumb and forefingers so that about an inch of the 3 inch width projected beyond the fingers with the remainder of the pad lying in the palm of the hand. The surface to be rubbed down was then to be wetted with water and the pad applied as if it were a paintbrush using circular strokes with very light pressure. Care was to be taken not to touch rivet heads and to use the least possible pressure when passing over other projections. The surface should be kept wet, and a fresh area of the abrasive paper exposed at intervals as necessary. After rubbing down, the surface was to be thoroughly cleaned with water and a scrubbing brush before being left to dry.
Type S paintes might have been introduced gradually from circa May/June/July 1940 onwards, and at roughly the same time, the requirement for the colour demarcation between camouflage colours to be a soft one was made no longer mandatory. As a consequence there is no clear picture as to which manufacturer followed which process, and with which materials, and at what time. It is not easy to tell whether the original matt paint was used and then sanded down which would impart a slight sheen, or whether Type S materials were used.
By December 1940, with the exception of Special Night, all aircraft camouflage paints, including identification colours, whether synthetic or cellulous based were supposed to be manufactured using Type S materials.
Airframes
Benevolens Magister
That's correct. Some RAF pilots did the same thing. However, the pic I posted of the actual Spitfire in question shows the standard smooth matt finish. It is possible that, before this particular aircraft went to 2TAF, it might have been polished for it's role in anti-Diver patrols, but there is no sign of this in the photo, or in photos of other MkXIVs of the squadron, and other squadrons in the Wing.
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