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Xtracolour neutral grey query


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#1 Graham

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Posted 31 December 2011 - 07:25 PM

Hi guys is Xtracolor neutral grey X133 a good match for the undersides of a B-17F??

Cheers

Graham

#2 spitfire

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Posted 31 December 2011 - 07:44 PM

Hi guys is Xtracolor neutral grey X133 a good match for the undersides of a B-17F??

Cheers

Graham


Here is a link to a thread that I started about Neutral Grey, basically the Xtracolor X133 is far too light (even though Xtracolor are my favourite paints), the one that you want is the WEM Colorcoats Neutral Grey 41.
http://www.britmodel...p...c=27570&hl=

Cheers

Dennis

#3 Graham

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Posted 31 December 2011 - 07:58 PM

Thanks for the info Dennis I will try WEM, I have an old tin of Humbrols Authentics neutral grey and it is pretty dark and that's why I asked about the Xtracolor as it's a lot lighter.

Cheers

Graham

#4 spitfire

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Posted 31 December 2011 - 08:05 PM

Thanks for the info Dennis I will try WEM, I have an old tin of Humbrols Authentics neutral grey and it is pretty dark and that's why I asked about the Xtracolor as it's a lot lighter.

Cheers

Graham


You are very welcome, your question was pretty much the same as mine !

Cheers

Dennis

#5 Seawinder

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Posted 01 January 2012 - 04:58 AM

Hi guys is Xtracolor neutral grey X133 a good match for the undersides of a B-17F??

Cheers

Graham


American WW2 Neutral Gray was produced by mixing black and white 1-to-1, which makes it pretty easy to make your own. I generally tweak it slightly lighter (like 60% white, 40% black) for scale effect. In any case, it was not the much lighter gray labeled Neutral Gray in various paint lines (Model Master's is 36270 -- quite close to British Medium Sea Grey).

Pip Moss

#6 Giorgio N

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Posted 02 January 2012 - 02:05 PM

American WW2 Neutral Gray was produced by mixing black and white 1-to-1, which makes it pretty easy to make your own. I generally tweak it slightly lighter (like 60% white, 40% black) for scale effect. In any case, it was not the much lighter gray labeled Neutral Gray in various paint lines (Model Master's is 36270 -- quite close to British Medium Sea Grey).

Pip Moss


Model Master is not completely wrong: FS.36270 is actually called neutral grey although it is completely different from wartime neutral grey. Among today's FS coded greys, the closer to wartime Neutral Grey 43 is FS 36173 AMC grey

#7 Nick Millman

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Posted 02 January 2012 - 03:42 PM

Model Master is not completely wrong: FS.36270 is actually called neutral grey although it is completely different from wartime neutral grey. Among today's FS coded greys, the closer to wartime Neutral Grey 43 is FS 36173 AMC grey


Neither of those greys is a pure neutral grey. In the form in which they are represented in FS 595B they both contain rutile titanium dioxide (white), phthalocyanine blue (red shade) and carbon black (blue shade). In addition 36270 contains benzimidazolone yellow whilst 36173 contains red iron oxide (blue shade).

In Archer's 'genealogical' table. Neutral Grey 43 goes no further than Bulletin 41 of Sep 16 1940 and no FS successors are given. Light Gray ANA 602 evolved into FS 36440. The pigments specified for Neutral Gray 43 in 14105 (camouflage pigmented nitrate lacquer) and 14106 (camouflage pigmented nitrate dope) were titanium dioxide, yellow iron oxide and lamp black - so not pure black and white after all. The closest FS value in terms of pigment only is 36492 which also contains titanium dioxide, yellow iron oxide and carbon black but of course the ratios are unknown.

Further the titanium dioxide in Neutral Grey 43 was not specified to be of chalk resisting type (rutile) as it was in the specs for Insignia White and Insignia Blue. This means it was probably anatase type with a known tendency for chalking. This would have the effect with exposure of making the grey gradually appear lighter.

#8 Chuck1945

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Posted 02 January 2012 - 04:29 PM

...Further the titanium dioxide in Neutral Grey 43 was not specified to be of chalk resisting type (rutile) as it was in the specs for Insignia White and Insignia Blue. This means it was probably anatase type with a known tendency for chalking. This would have the effect with exposure of making the grey gradually appear lighter.

Which could be at least a partial explanation why so many photos appear to show a Neutral Gray 43 that is lighter than the specified shade.

Thanks for your information here Nick. Neutral Gray as a 50-50 combination of black and white is one of those tidbits of data accepted as a 'fact' by many of us, myself included. Time to change that misconception.

#9 Graham

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Posted 02 January 2012 - 04:39 PM

Hi Nick so would the grey go lighter as the 17 I am doing was built in early 1942 and spent all her time with the 99th BG in North Africa and I have had conflicting replies as to whether it would fade to a light grey or just slightly lighten?? As mainly being on the underside of the aircraft and it would be out of direct sunlight would it fade at all or just the parts i.e. the engines and fuselage sides which would get the sun?

Thanks

Graham

#10 Nick Millman

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Posted 02 January 2012 - 05:20 PM

Hi Nick so would the grey go lighter as the 17 I am doing was built in early 1942 and spent all her time with the 99th BG in North Africa and I have had conflicting replies as to whether it would fade to a light grey or just slightly lighten?? As mainly being on the underside of the aircraft and it would be out of direct sunlight would it fade at all or just the parts i.e. the engines and fuselage sides which would get the sun?

Thanks

Graham


The typical effects of chalking result in a whiteish-grey patina across the surface which is not that obvious to the eye unless you rub your hand over it. Titanium dioxide is both a UV-activated oxidation catalyst and a UV absorber. As an oxidation catalyst free radicals are formed on the surface and oxidise the binder by photocatalytic degradation. This reduces any gloss and produces a friable layer on the surface of the paint film. So the process will be exacerbated under direct UV exposure but even surfaces out of direct light will not be immune, for example a combination of extremes of heat and humidity will cause a similar degradation. Any paint that contains a majority of anatase titanium dioxide (like greys and light blues) would tend to display more chalking, which is why Ocean Grey, say, can appear to "fade" much lighter than Dark Green.

The typical effect on a grey paint would be to make it appear lighter but you could expect the surface to be variegated rather than even, especially where it has been subjected to different degrees of exposure. How light depends on the duration of exposure, reaching a point where it could be almost off-white and eventually the paint would break down through the whole film. Regular maintenance treatment will reduce the process or delay it but not eradicate it entirely.

When you use something like T-Cut colour restorer on old car paint you are effectively abrading through this degraded friable layer to expose the unaffected paint film underneath.

#11 Jennings Heilig

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Posted 02 January 2012 - 08:20 PM

Model Master is not completely wrong: FS.36270 is actually called neutral grey although it is completely different from wartime neutral grey. Among today's FS coded greys, the closer to wartime Neutral Grey 43 is FS 36173 AMC grey


That misquote linking FS 36270 to wartime Neutral Gray 43 goes way back, and Testors simply perpetuated it. FS 36270 is in no way related to the WWII color. The descendant of the WWII color is in fact FS 36173 and always has been. That's why it's risky to use names in association with FS595 colors. They don't have official names for that very reason. Unless you transpose numbers, it's impossible to mix up 36173 and 36270.

J

#12 Graham

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Posted 02 January 2012 - 08:23 PM

Did a bit more digging and the 17 I am building was delivered on 22/12/42 so going by the link in Dennis's thread she should have been painted in the ANA colour and as she completed a 111 missions I would think her colours would be pretty washed out before she was withdrawn from front line in Dec 44. As I am planning to show her late on in her service would the lighter Xtracolor be the better shade to go for rather than the factory fresh WEM paint??

Thanks

Graham

#13 Chuck1945

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Posted 02 January 2012 - 08:45 PM

Did a bit more digging and the 17 I am building was delivered on 22/12/42 so going by the link in Dennis's thread she should have been painted in the ANA colour and as she completed a 111 missions I would think her colours would be pretty washed out before she was withdrawn from front line in Dec 44. As I am planning to show her late on in her service would the lighter Xtracolor be the better shade to go for rather than the factory fresh WEM paint??

Thanks

Graham

You are part right, from the info Nick provided, the paint would have chalked to some extent. But, drop any reference to ANA, the USAAC continued to accept aircraft finished in the OD 41 and Neutral Gray 43 colors until the camouflage requirement was dropped. Aircraft producers were permitted to use 41 and 43 while stocks lasted and plenty of both would have been aavailable throughout 1942.

The committees that eventually set the ANA colors began work in 1942 but finalizing the colors didn't happen until mid-late 1943 (reference the Archer (USAAF) and Elliott (USMC/USN) books). Even then there remains considerable doubt that any USAAC aircraft were finished using them, especially aircraft headed to Europe/Middle East.

#14 Nick Millman

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Posted 02 January 2012 - 08:51 PM

Did a bit more digging and the 17 I am building was delivered on 22/12/42 so going by the link in Dennis's thread she should have been painted in the ANA colour and as she completed a 111 missions I would think her colours would be pretty washed out before she was withdrawn from front line in Dec 44. As I am planning to show her late on in her service would the lighter Xtracolor be the better shade to go for rather than the factory fresh WEM paint??

Thanks

Graham


I doubt it would be the ANA replacement for Neutral Gray which was Sea Gray 603 as that colour was only introduced in ANA 157 on Sep 28 1943 and went on to become FS 36118. If you mean the WEM ACUS13 that is labelled "WW2 USAAF Neutral Gray ANA 43" so I suppose it is intended to represent Neutral Gray 43. It is not as dark as 36118 but darker and more blueish than X133 which is also labelled as matching FS 16270!

I don't know where the link between Neutral Gray 43 and FS 36173 comes from except by it being matched by eye at some point. As noted above FS 36173 contains both blue and red pigments which the original Neutral Gray did not have.

#15 Graham

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Posted 02 January 2012 - 09:18 PM

Ok guys can I put you on the spot and ask if you know what paint would best represent a well worn neutral grey and thanks again for all your input to this thread.

Graham.

#16 Nick Millman

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Posted 03 January 2012 - 12:41 AM

Ok guys can I put you on the spot and ask if you know what paint would best represent a well worn neutral grey and thanks again for all your input to this thread.

Graham.

Difficult call as I don't use that paint colour much. Crunching the numbers the closest FS value to actual Neutral Gray 43 is 16187 but although very close that is gloss. The closest RAL is 7005, even closer, and Revell supposedly match that colour with Matt 47 Mausgrau (Mouse grey). I have a tin of that and although I haven't painted out a swatch it looks pretty good. It is about the same darkness as the WEM but not as cool or as blueish and if you added a touch of white I think it could be ok to represent an oxidised Neutral Gray 43. Revell 47 is supposedly matched by Humbrol 106 Ocean Grey but that is a little purplish by comparison.

16187 is just a tiny bit greenish as it contains phthalocyanine green (blue shade). RAL 7005 is also slightly greenish but not quite as much and is a little lighter than Neutral Gray. Both are slightly warmer as you would expect with grey paints containing yellow. The effect of the yellow oxide with carbon black is to create a very subtle greenishness anyway.

#17 Graham

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Posted 03 January 2012 - 03:39 PM

Cheers Nick, thanks for all your help I will have a look at the Revell 47.

Graham

#18 Chuck1945

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Posted 03 January 2012 - 04:57 PM

There have been two issues at play here, or at least so it seemed to me. First, was ANA 603 used on a B-17 built in 1942 with answer being 'no, not at all likely', this being what my previous reply was addressing. Second, and perhaps the real question, what is a good paint recommendation to represent faded (or chalked) Neutral Gray 43?


Photos of camouflaged B-17s, as well as fighters, portray NG anywhere from a very dark color to one quite light. I don't have a good explanation for this, whether there really was a great deal of variation in the actual paint used, vagaries in period b&w film, different filters, or lighting or whatever... In any case to represent a faded or just lighter version of NG 43 simply choose a lighter grey that remains relatively neutral. As Nick pointed out, the chemical composition of NG 43 included more than just black and white pigments, but the idea of mixing black and white stays rather true to what NG was - a grey without any strong blue or yellow tendencies. When I model a camouflaged USAAF WWII aircraft, I usually choose something lighter than NG 43, most recently choosing FS 36231 (Gunze H-317). As a caveat, my choice is based solely upon eyeball impressions using artificial lighting.

#19 Jennings Heilig

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Posted 03 January 2012 - 07:53 PM

Photographs are very poor color research tools. There are so many variables in the process, no two photos of the same airplane taken on the same day with the same roll of film will come out looking identical.

A wise veterinary physician I worked with once told me "Don't look for a zebra when there's a donkey in the barn". In other words, common things (NG 43 undersides) occur commonly. That's why they're common. I can give you just about an iron clad guarantee that every B-17 that left the factory in OD/NG was pretty close to the same color on the bottom, and that that color is considerably darker than most modelers recognize. I've seen lots of original WWII artifacts with NG 43, and it's a pretty dark color. Did it fade in service? Undoubtedly, but keep in mind that the bottom sides of airplanes don't see much of the sun. Northern European weather isn't the same as South Pacific or North African weather, so paints didn't weather the same way, nor nearly to the same extent. Airplanes in the UK operated (for the most part) off of hard surface runways, not mud and dust. I'd just go with a paint that matches NG 43 and lighten it for scale effect and call it good.

#20 Nick Millman

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Posted 03 January 2012 - 09:28 PM

Whether the barn contains zebras or donkeys, it's not just direct sunlight that affects paint surfaces and the result is not just fading.

In the exposure environment the chemical and physical processes are complex. The paint surface is subjected to diverse and variable environmental stresses. The most significant are heat, oxygen, sunlight, water (both in liquid and vapour form), mechanical and thermal stresses, atmospheric pollutants and various chemicals. The paint film contains decreasing levels of residual solvent or water or both retained after application, as well as pigments, fillers, additives or trace metal impurities incorporated during manufacture - all of which will probably have some photochemical activity. In the case of NG43, the main pigment anatase titanium dioxide* is known to be prone to chalking.

The B-17 to be modelled, as I understand it, was a two year old 111 mission veteran of service in North Africa. I would be very surprised if the paint surface matched a swatch of NG 43 just lightened for scale effect.

*From the Colour Index section on Inorganic Colouring Matters (my emphasis):-
77891 C.I. Pigment White 6 Titanium dioxide TiOl
Ilmenite, FeO.TiO, a natural mineral, is digested with sulfuric acid, the solution hydrolysed and the precipitated titanium dioxide separated, calcined and ground. Some commercial grades are reduced with barium sulfate or calcium sulfate. The rutile variety is also mined
The pigment exists in three forms:-
1 Anatase which has great tendency to chalk on exposure but which has good hiding power
2 Rutile a thermostable variety having little tendency to chalk
3 Brookite an orthorhombic variety of little importance