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Exhaust colours


AltcarBoB

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I am painting a 1/72 Fairey Fulmar MkII and I am about to paint the exhaust stubs. In the dim distant past I always just painted the exhausts brown and left it at that but I am discovering the dark arts of dry brushing. How long would a RR Merlins exhaust stubs stay the original shiny steel colour and would they rust or just get a bit sooty and dull.

 

What's your favourite colour scheme for exhaust systems, I was thinking of Vallejo Steel mixed with some black to tone it down for the base coat then dry brushing with with a dark red and finished with a light dry brushing of black.

 

 

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My impression from looking at the resurrected Spits and Hurricanes that are still flying is that the forward manifol exhaust stays pretty much the shiny silver colour of the original s/s, while the aft exhaust stubs get all the carbon deposits from start up, causing them to blacken and also to take on that silvery/blluey/purpley/reddish hue that s/s can show when continually subject to hot gas and carbon. I guess there's no fixed pattern to this but experiments based on colour pics would be a good shout. Sorry not to be too specific. Paul

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I am not anywhere close to my paint stash (like about 65 miles away) so cant give jar references, but anymore I usually paint the stubs a dark iron or burnt metal, and then dry brush Tamiya clear orange and/or clear blue

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11 hours ago, Pauls9cb said:

My impression from looking at the resurrected Spits and Hurricanes that are still flying is that the forward manifol exhaust stays pretty much the shiny silver colour of the original s/s, while the aft exhaust stubs get all the carbon deposits from start up, causing them to blacken and also to take on that silvery/blluey/purpley/reddish hue that s/s can show when continually subject to hot gas and carbon.

I concur, with the addendum that the after stubs can also be highlighted by white lead deposits.  If I understand correctly this is due to the use of highly leaded gasoline run at a lean mixture for extended time periods-- someone correct me if I've got it wrong!

 

11 hours ago, AltcarBoB said:

Thanks I hadn't noticed that the exhausts showed different colours front to back but it is logical thinking about it

 Yep, it's totally a thing.  Once it was pointed out to me I could never not notice it again.

 

My older method was to prime with a rusty red, highlight with a tannish colour, apply dark wash, and finish highlight with dry brushing or pencil graphite as references dictate.

 

I've lately borrowed an armour technique of painting the exhausts a metallic colour followed by pebbly transparent oversprays of bluish and rusty colours.  I actually used a purple made from Tamiya Red Brown and XF-8 Blue on my P-38F, I was nervous about so bold a choice but it really looks the part.

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I usually spray with a metallic mix Tamiya Aluminium/ Dark iron over the whole exhaust.  I mix in some dark blue or red and lightly brush in from the curve of each pipe towards the open end of the exhaust.  Dry brush with a bit of brass.  Spray the exhaust mix I am going to use for the fuselage staining backwards from the first pipe over the top of the second and third pipe...

 

My SH 1/48 Fulmar.

35438670762_079613716e_c.jpg

 

There are some great close up shots of the restored Sea Hurricane on the Internet.  I tried to base my exhaust on those pictures..

 

Hope this helps..

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I have had a go at the exhausts this morning. I decided to mix up a Vallejo reddish brownish plumish mix and do a base coat then I drybrushed Vallejo Steel on trying to shade it so that the rearmost stub was least steel coloured then I dabbed on some very dry black also staining the fuselage aft of the exhausts. Typically it never quite works on camera but I think its a lot better than the plain brown I always did back in the day

 

49668466173_94df40d171_c.jpgIMG_20200317_105401194 by Stuart, on Flickr49668464263_660ff7e1cd_c.jpgIMG_20200317_105357703 by Stuart, on Flickr

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21 hours ago, AltcarBoB said:

How long would a RR Merlins exhaust stubs stay the original shiny steel colour and would they rust or just get a bit sooty and dull.

study period colour photos

I really recommend @Etiennedup flickr where he has collated a lot of WW2 colour

for ease, if you use this

https://www.flickr.com/search/?text=spitfire&user_id=8270787%40N07&view_all=1

 

You can just type in a different aircraft type,  as there are quite a few Spitfire pics, and they have the same engine and stacks..

 

16804377395_8b7c604c60_o.jpgSpitfire Mk. IIA, 1941. by Etienne du Plessis, on Flickr

 

note how the lead bromide deposits build up on stack 2/3

 

40081280613_6281cac994_o.jpgRCAF Spitfire Mk. V, 1943. by Etienne du Plessis, on Flickr

 

14780326836_c9727d9f2c_o.jpgRCAF Spitfire V,  1943. by Etienne du Plessis, on Flickr

 

8602734232_c6547a543c_o.jpgSpitfire L.F. mk.V,   6 August 1943. by Etienne du Plessis, on Flickr

 

5563260675_6691af78c1_o.jpgSpitfire in Malta 15 May 1943. by Etienne du Plessis, on Flickr

 

41402963810_fe3e328e1e_o.jpgSpitfire Mk.II, 1941 by Etienne du Plessis, on Flickr

 

here's the Hurricanes

https://www.flickr.com/search/?text=hurricane&user_id=8270787%40N07&view_all=1

 

this is good one

23237102681_c67155050c_o.jpgRCAF Hurricane XII, c1941. by Etienne du Plessis, on Flickr

 

As you can see, they vary.  a metallic base coats, with washes, and chalk pastels is a way, but,  if what you use gets you results you like, it's the right technique.

we have an excellent walkround of the Shuttleworth Sea Hurricane here

 

 

sh09.jpg&key=5d0d3bb3488a7c006c86efeb173

 

in shadow

Sea%2520Hurricane-020.JPG&key=2675053241

 

this came up when I actually built AND finished a model

  

On 20/03/2019 at 22:27, dogsbody said:

I painted my exhaust pipes Tamiya XF-84 Dark Iron and did a bit of weathering with Tamiya Pastels Burnt Red. They will need some lighter colours yet.

 

46072033212_dd5651595b_b.jpg

 

  

On 21/03/2019 at 10:20, Troy Smith said:

i did mine first in a mix of gunmetal and dark blue, which would make a nice party dress... then tried a Vallejo rust wash,  which made sparkly orange, so tried dulling it down with my grey wash and some hull red,  and then dabbed on some very thinned blue,  wiping off the excess each time.... which got me here

 

32491546317_bd3727092d_b.jpg

 

XF-84 Burnt Iron might be easier....

 

 

So, to sum up study photos and experiment.

 

HTH

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I just had a thought. What would the exhaust looked like on the early Hurricanes, like those used in France and the fabric-winged Hurcs that went to Canada in 1939.

Would they have access to higher octane fuel with TEL added? Would the pilots of those aircraft have pushed the engines to their maximum limits, as they would in combat?

 

 

 

Chris

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Had another go I have darkened the first exhaust stub and added some pale grey to the 2nd and 3rd stub to show the Lead whitening. Still cant seem to get the real tinge which looks almost a clay colour not white not grey. I might try a bit of white with some brown (a very little bit of brown) to get that almost biscuity colour

 

49670377947_24701485ee_c.jpgIMG_20200317_174325300 by Stuart, on Flickr

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Hello!

 

To my eyes the exhausts in the photos Troy linked are (were) painted black. Temperature changes (use) and environment has then done it's work on the exhausts.

Did Brits use chemical treatment/ paint Kemick? Germans certainly did on DB 605 exaust stacks and the name appears also in Finnish war time documents.

 

The name does not sound very German and I run a quick google search. This time found this nugget, I quote:

 

"Paint for Hot Metal

HOT metal surfaces are as subject to rust and corrosion as are cold ones, but no ordinary paint can be used to give them proper protection. A new chemical rust-preventing paint, named Kemick, has been developed for such hot metal surfaces. This finish, which is made by the American Chemical Paint Company, may be used on hot parts of the automobile engine, such as exhaust manifolds, exhaust pipes, and mufflers. Not only will it protect the metal, but it also makes a more sightly engine.

Kemick becomes effective through chemical action with the metal which it covers. Whereas ordinary manifold and engine enamels decompose quickly and completely when subjected to heat Kemick decomposes only partly, the volatiles are expelled, and chemicals are liberated to react on the metal surface. It does not burn off but retains its co!or and protective properties and is said to improve with heating —Scientific American."

 

https://archive.macleans.ca/article/1940/9/15/invasion-threat---1588

 

In this forum there are many people with better google-fu than I. I would be more than interested to know what the Kemick was (paint or some chemical treatment) and from where it did originate.

 

If you ask me, I would paint the inline engine exhaust stacks black all over and start weathering from that.

 

Cheers,

Kari

 

spacer.png

Edited by Kari Lumppio
Changed the picture url for the correct one
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Post Scriptum

 

Flight International 1932-08-12 (pity that the pdf-archive in not working at present) has article of the Kemick, too:

 

"HEAT RESISTING PAINT FOR EX- HAUST MANIFOLDS A N entirely new development in Uie ^ painting of engine parts is the discovery of a new paint, known as “ Kemick ” Heat-Resisting Paint, which is at once a rust-preventative and actually improved by intermittent heating and cooling action. Until now there has been no known material which could be satisfactorily- applied to exhaust systems to preserve them from rust for any appreciable length of time. However clean the other parts of an engine, the eflect is spoilt by the rusty and dirty surface of the exhaust system. “ Kemick,” it is claimed, will give this an appear- ance as good as the rest. It will not come oil or bum off hot metal at red or even white heat, and its efficiency as a rust-preventative is in no way lessened at these extreme temperatures. ” Kemick ” is a paint with a liquid and volatile content which serves to spread the material evenly on the sur- face and hold the pigment in place before heating. Moreover, heat which decomposes ordinary paint to worth- less ashes, changes “ Kemick ” by a chemical process into a finish which will adhere to the surface and prevent rust for an indefinite period. It re- tains its colour at all times. When applied it is black, but when heated it bubbles slightly and liberates a fine white powder which, mixed with the black pigment, gives the surface a dark grey colour. It requires no skill in application, and the surface to which it is applied need not be as clean and polished as would be re- quired for an ordinary enamel, although all old paint, oil, grease and loose scaly rust should be removed with a wire brush or sandpaper. Two coats of “ Kemick " are recommended and it is advisable, where possible, to heat the surface after the first coat and before the second is applied. ” Kemick ” is equally satisfactory' on steel, iron, zinc, galvanised iron, copper, brass, tin or aluminium. The manufacturers of this new pro- duct are Nobel Chemical Finishes, Ltd. (associated with I.C.I.j, of Slough, Bucks."

 

So certainly a known system all over the aviation world by 1939.

 

I can answer my own question that it was "made in USA" by American Chemical Paint Company (APC) originally.

 

U.S. Patent Office magazine (June 7, 1921) gives for the Kemick "Particular description of goods - Paint That is Used to Advantage on Surfaces Exposed to Heat.
Claims use since Jan. 10, 1921"

 

Cheers,

Kari

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On ‎16‎/‎03‎/‎2020 at 16:44, AltcarBoB said:

I am painting a 1/72 Fairey Fulmar MkII and I am about to paint the exhaust stubs. In the dim distant past I always just painted the exhausts brown and left it at that but I am discovering the dark arts of dry brushing. How long would a RR Merlins exhaust stubs stay the original shiny steel colour and would they rust or just get a bit sooty and dull.

 

What's your favourite colour scheme for exhaust systems, I was thinking of Vallejo Steel mixed with some black to tone it down for the base coat then dry brushing with with a dark red and finished with a light dry brushing of black.

 

 

Even on a freshly restored aircraft where the engine has had limited run time they are not bright

 

be505%2027.JPG

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2 hours ago, Julien said:

Even on a freshly restored aircraft where the engine has had limited run time they are not bright

 

be505%2027.JPG

 

I would love to be able to play with a 12 inches to the foot scale Merlin

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There were two exhaust paints available. The first was red lead based used to disguise the glow of the exhausts at night. Found on aircraft such as Wellingtons. The second was white used to camouflage the collectors on Coastal Command aircraft that were painted white.

 

RR exhausts were made from Inconel, an alloy of nickel and chromium. The problem with steel is that it distorts at high temperature. Nickel retains its strength at high temperature. Chromium gives it resistance to corrosion.

 

The natural colour is light brassy similar to £1 coins. It quickly forms a thick, protective, oxide layer and takes on a brown colour like Dark Earth.

 

There is a thread on the Key Publishing forum on inconel exhausts. Since it was revamped everything saved in my ‘favourites’ results in the good old 404 page not found. However I have managed to find it.

 

https://www.key.aero/forum/historic-aviation/143045-historic-aviation-metallurgy-exhausts

 

If you page through at about the 7th post there is a RR document on exhausts. You are unlikely to be able to read it on screen now. You will have to right-click and save image so you can look at it in your favourite photo-viewer.

 

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Hello!

 

I read with interest the linked thread of inconel exhausts. Thank you 303sqn.

 

I quote from the first document photo (attachment) there (the Rolls Royce exhausts -posting):

"Previously inconel was used for all Rolls-Royce manifolds...

Due to the difficulties in the supply of nickel during the war it has been necessary to use metals with lower nickel content."

 

I do not want to be argumentative. In this case the lower nickel content meant stainless steel which does not need Kemick or similar protection.

 

 

Cheers,

Kari

 

 

Edited by Kari Lumppio
Typo corrections
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Hello

After all the dirt and clay had been removed from exhausts of remains of the Spitfire IX, dug out nearby last October, a dark, slightly metallic brown colour had been revealed. This is consistent with what can be seen on many colour wartime photos of Merlin 60 series powered aircraft. Probably this is not inconel stainless steel 303sqn mentioned, but, as Kari wrote, one of the less heavily alloyed nickel chromium steels, also mentioned in the document.

Thinking about it, what was the situation with US produced Merlins? Exhausts on colour photos of Packard-Merlin powered Mustangs all look pretty dark to me. Cheers

Jure

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On 3/17/2020 at 6:11 PM, Kari Lumppio said:

I would be more than interested to know what the Kemick was (paint or some chemical treatment) and from where it did originate.

The description of ‘Kemick’ (is it a word play on chemical?) and ‘American Chemical Paint Co’ suggests it is a chemical treatment rather than a paint in the conventional meaning. Bubbling and white deposits makes me suspect that phosphoric acid is involved.

 

Cannot find a patent for anything called Kemick but there is a patent for a method of making propeller blades that mentions it as being used as a coating for the blades. They are first cleaned with a substance called Deoxidine. And whatda you know, Deoxidine is also from the ACPCo stable. So looking there we find -

 

“James Harvey Gravell was an engineer, innovator, and philanthropist born in Philadelphia in 1880. While employed by Hale-Kilburn Metal Company, Gravell helped develop a chemical treatment for preventing rust and peeling on painted metal. He purchased the patent for the “Deoxidine,” and started his own company, the American Chemical Paint Company, in 1914. After operating in a rented space in Philadelphia, Gravell opened a chemical manufacturing and research facility in Ambler. The company was extremely successful, and Gravell became a rich man. He donated money to a number of worthy causes, including giving his employees the best Christmas ever.”

 

Gravell is the key, he has patents for all sorts of things, among them one for improvements in metal pickling.

 

From this patent we learn that Dioxidine is a mixture of alcohol and phosphoric acid and the process is to treat the pickled metal with a solution of sodium silicate which converts metal oxides to insoluble silicates which form a protective coating resistant to corrosion.

 

This is probably not Kemick but looks to me that Kemick is a development of this process and that involves phosphoric acid and sodium silicate to form stable and resilient protective coating on ferrous metals.   

 

US2081645A - Method of producing propeller blades:

 

https://patentimages.storage.googleapis.com/a7/7d/f2/1589c962746f8d/US2081645.pdf

 

US1555798A - Metal pickling

 

https://patentimages.storage.googleapis.com/a0/06/56/be11df53362a51/US1555798.pdf

 

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