Jump to content

Recommended Posts

I use grey but vary it between vehicles, as different times out of the shops and different environments would have meant that they were not uniform. A useful way of using up those oddments of grey paint, especially if like me you are modelling pre-grouping.

Jonathan

  • Like 2
Link to post
Share on other sites
  • RMweb Gold

Never pure white (apart from when freshly painted) but a slightly weathered white and every shade of dirty grey in between that and absolutely filthy.

 

7 hours ago, dpgibbons said:

Depends if you want a factory fresh vehicle - GWR white roofs quickly turned to grey due to grime and oxidation of the lead pigment.

 

This is a very misleading statement, how quick is "quickly"?  I've seen some people (not saying you) suggest a matter of days without any evidence at all! There is plenty of photographic evidence to show that "white" roofs were a lot more numerous than people keeping repeating the same old memes that you would never see them in service. Here's an Example of Taunton from Britain From Above website:

WhiteRoofsDontExist.jpg.063eea8b74eb19af38c6ad4644743894.jpg

 

Not every roof would be white, but then not every single one would be grey/black either. The key is variety. Also don't forget, that lead white is not a pure white colour, it's an off white to start with.

 

 

 

 

  • Like 2
  • Agree 3
  • Informative/Useful 2
Link to post
Share on other sites

I model 1948 so any white roofs (stopped in WWII?) would be quite weathered by then.  I have some stock with bright white roofs painted before I knew better.  When upgrading, I weather or use grey but try and vary it a bit.  There are photos on the forum of coach roofs where the white is weathered very differently at one end to the other (eg autocoaches that always had the loco at the inner end).

 

Will

  • Like 1
Link to post
Share on other sites

This gets discussed fairly regularly on RMWeb & elsewhere & I remember it being observed that whereas white van roofs appeared in greater numbers than many assume it does seem that white carriage roofs were much rarer - they seemed to discolour quicker. It was suggested that carriages spent a greater percentage of their lives actually running behind steam locos & so were subject to more loco exhaust than vans which spent a lot of their lives idle in goods yards. An interesting theory.

 

Martin

  • Like 2
  • Agree 1
  • Interesting/Thought-provoking 1
Link to post
Share on other sites
  • RMweb Gold
3 hours ago, WillCav said:

I model 1948 so any white roofs (stopped in WWII?) would be quite weathered by then.  I have some stock with bright white roofs painted before I knew better.  When upgrading, I weather or use grey but try and vary it a bit.  There are photos on the forum of coach roofs where the white is weathered very differently at one end to the other (eg autocoaches that always had the loco at the inner end).

 

 

Good point about post-war GWR, my comments are more related to pre-WWII. Having said that I have a 1950 pic that shows a small sprinkling of very light roofs on a train of vans still, so not totally unfeasible.

 

I posted a pic of the railmotor at Didicot showing just that sort of weather on it's roof, heavier at the engine end, very little at the far end. Also check out the clerestory coach at the front of the train in 1929. Surprisingly clean compared with the others! As Martin said, from the pics I have collected, they do seem a lot rarer on coaches though, not totally absent.

 

Westbury1929-2.png.6c58a57f156051f5a5377b7d48b8edd9.png

  • Like 1
Link to post
Share on other sites

I reckon that the "everything was dirty and rusty" is a bit of a misnomer.

 

Look at the colour photos in this book and see all the dirty engines, carriages and wagons. Very few of them, even in the background.

 

https://www.amazon.co.uk/Big-Four-Colour-1935-50/dp/0906899621

 

Even the cover shows a very presentable red Jubilee and train post war. ISTR the photo is dated 1949 but nearly all the stock is still in pre war livery and cleanish.

 

 

 

Jason

  • Like 1
  • Agree 1
  • Informative/Useful 1
Link to post
Share on other sites
  • RMweb Gold
2 hours ago, Steamport Southport said:

I reckon that the "everything was dirty and rusty" is a bit of a misnomer.

 

That has definitely become one of the modelling memes floating about.

  • Agree 2
Link to post
Share on other sites

I have had many interesting conversations with friends who have considerable coach research. I get told off as, although  the white roof discoloured very quickly, a black roof is a stoning offence. Key express sets would be cleaned on a regular basis, including the roof, but other sets the outside, including the roof was not cleaned as often.

 

My Torbay Express has all clean white roofs as Old Oak cleaned the set that morning. A have a few others and my Hornby non corridor set is still as bought....but not for long.

 

My roof sections tend to be grey. I spray them with Holts Rover Tempest Grey. For non express vehicles, I tend to give an additional blow over with a quick pass of white and a final quick waft of black, to add some hint it was once white. ( it's all in the wrist action!)

 

Clerestories do look good with  a two tone roof. For the white section I prime with Holts grey and put a light coat of white with the grey showing through. Now I have too many clerestories, not long out of the paint shop, but it is my trainset!

 

Mike Wiltshire

  • Like 2
  • Informative/Useful 1
Link to post
Share on other sites

White carriage (or wagon) roofs had very little to do with frequency of cleaning but everything to do with the quality of air in the areas where they worked (notably the concentration of H2S) and how recently they had been repainted.

 

The white paint used was a white lead-based paint and as such subject to chemical conversion of the white lead oxide component to very dark grey lead sulphide. How quickly this happened would have depended on air quality, gas woks  were notable producers of low atmospheric concentrations of hydrogen sulphide (hence the typical gas works smell) but so was much marshland, so vehicles used only on country branches could be as susceptible to darkening roofs as those based in urban areas. The darkening of roofs had little to do with soot, except perhaps close to the chimney on rail motors, as rain would wash most soot off when it fell.

 

It seems likely that there was also a white lead component in the cream paint used on GWR carriage panels and it was this that caused those same panels to darken over time as a result of the same chemical process, inhibited to some extent in this case by the varnish coating.

Edited by bécasse
"lead sulphide" corrected to "hydrogen sulphide"
  • Like 2
  • Agree 1
Link to post
Share on other sites
  • RMweb Gold
6 hours ago, bécasse said:

How quickly this happened would have depended on air quality, gas woks  were notable producers of low atmospheric concentrations of lead sulphide (hence the typical gas works smell)

 

Presuming you meant hydrogen sulphide there. ;)

Link to post
Share on other sites

All this discussion of the reaction of lead oxide mystifies me. According to Wikipedia white lead is a complex mixture principally composed of lead carbonate.

My GCSE level understanding of chemistry is as follows:

Hydrogen sulphide gas is I believe relatively unreactive (and the sulphur is less reactive than oxygen so would not displace it from lead oxide anyway) and would disperse quickly in the atmosphere. In the atmosphere hydrogen sulphide would dissolve in water droplets forming sulphuric acid (acid rain). This would react with lead carbonates to form carbon dioxide, water and lead sulphAtes, which are also white, but possibly importantly are soluble.

 

With regard to the role of carbon (soot). Carbon is more reactive than lead so would displace it producing carbon dioxide and lead metal, (this applies to lead oxide too) which is of course grey. At atmospheric temperatures however this would be a very slow process. However none of this takes into account any effect of the oils used in the paint formulation to inhibit or alter these reactions.  We need a paints chemistry specialist for that.

 

The soot in the atmosphere would be composed of very fine particles (microscopic) which, much like weathering powders, would adhere to any non-glossy  or oily surface and would not easily wash off (think of buildings in the industrial heartlands). It is often hard now to appreciate just how much soot there was. A lecturer at Leeds uni. once told me that in the 60s a sheet of white paper left by an open window would turn grey by the end of the day.

 

So the suggestion that coach roofs were more subjected to soot from being behind a locomotive seems a reasonable one.

 

Just as an aside my Dad always swore that the old lead white gloss he used to paint window frames with had far better colour fastness than modern lead free paints.

  • Agree 1
Link to post
Share on other sites
  • RMweb Gold
20 hours ago, GWR_Modeller said:

Hydrogen sulphide reacts with lead carbonate to create lead sulphide, which is grey. In general terms Hydrogen sulphide is reactive rather than not.

What's the formula for that reaction?

Link to post
Share on other sites

I suppose it would be H2s(g)+pbco3 = pbs+h2o+ co2(g) in simple terms.  I do not know that reveals any more than the original sentence did.  It has been a very long time since I studied chemistry and I am sure paint pigment was not simple lead carbonate alone and the reactions are more varied and complicated than that.

Link to post
Share on other sites
On 18/09/2020 at 12:41, Darwinian said:

All this discussion of the reaction of lead oxide mystifies me. According to Wikipedia white lead is a complex mixture principally composed of lead carbonate.

My GCSE level understanding of chemistry is as follows:

Hydrogen sulphide gas is I believe relatively unreactive (and the sulphur is less reactive than oxygen so would not displace it from lead oxide anyway) and would disperse quickly in the atmosphere. In the atmosphere hydrogen sulphide would dissolve in water droplets forming sulphuric acid (acid rain). This would react with lead carbonates to form carbon dioxide, water and lead sulphAtes, which are also white, but possibly importantly are soluble.

 

With regard to the role of carbon (soot). Carbon is more reactive than lead so would displace it producing carbon dioxide and lead metal, (this applies to lead oxide too) which is of course grey. At atmospheric temperatures however this would be a very slow process. However none of this takes into account any effect of the oils used in the paint formulation to inhibit or alter these reactions.  We need a paints chemistry specialist for that.

 

The soot in the atmosphere would be composed of very fine particles (microscopic) which, much like weathering powders, would adhere to any non-glossy  or oily surface and would not easily wash off (think of buildings in the industrial heartlands). It is often hard now to appreciate just how much soot there was. A lecturer at Leeds uni. once told me that in the 60s a sheet of white paper left by an open window would turn grey by the end of the day.

 

So the suggestion that coach roofs were more subjected to soot from being behind a locomotive seems a reasonable one.

 

Just as an aside my Dad always swore that the old lead white gloss he used to paint window frames with had far better colour fastness than modern lead free paints.

 

Urban myth about buildings being covered in soot I'm afraid.

 

It's one of those ideas trotted out by environmentalists even back in the day.

 

When they clean buildings such as the Palace of Westminster and ones such as the Liver Buildings in Liverpool it is the stone naturally darkening with age which turns them dark, not pollution and certainly not "soot".

 

They are just going back to their natural colour. It's only when they are freshly cut that they are bright colours, but people like them that way so they are constantly cleaning them to make them look new. Thereby causing more damage than if you left them to naturally go dark.

 

It's a geologist you need to talk to, not a chemist.

  • Like 1
Link to post
Share on other sites

It can certainly be pollution causing stone to discolour even if it was not staining by black soot deposits.  In the atmosphere as a result of coal, petrol and diesel burning there is a concentration of sulphides, sulphites, sulphates, nitrous oxides, nitrites, nitrates, often in form of acids, lead compounds, carbon monoxide and loads of other stuff which would not be there in those quantities except as a result of burning fossil fuels.  

Limestones, containing magnesium and calcium carbonate compounds, react with some pollutants and discolour.  In addition the presence of some pollutants or their decomposition products on stone surfaces provides nutrition for microbial growth also causing discolouration.  Blackening may be a 'natural' process but it was certainly speeded up by pollution.

On the plus side I did hear that it was possible to grow very good roses downwind of coal burning power stations because the activity of the pollutants reduced black spot desease so not all bad.

 

Link to post
Share on other sites
  • RMweb Gold
20 hours ago, GWR_Modeller said:

I do not know that reveals any more than the original sentence did.

 

It shows some proper thought and knowledge of the subject rather than the oft repeated parroting of some incorrect information that we often get. :) I was also curious as to the other by-products of the reaction.

Link to post
Share on other sites

The chemical darkening of white roofs (or grey wagons for that matter) painted with white lead based pigments is well-established. However, by the 1930s, white lead was being replaced by zinc white - certainly in the LMS's formula for wagon grey. Because zinc is more reactive than lead, its compounds are more stable; it does not undergo a displacement reaction with hydrogen sulfide as does lead carbonate. So, when did the Great Western switch? Perhaps aerial photos date mostly from after the change in chemical composition of carriage roof paint so white roofs are more prevalent than in, say, the 1920s or earlier? Discolouration of a zinc white roof would be attributable to grime, so amenable to cleaning.

 

Also, I've read that the exhaust from superheated locomotives was much dirtier than from saturated locomotives, containing a proportion of oily substances. 

Edited by Compound2632
  • Like 1
Link to post
Share on other sites
On 16/09/2020 at 13:11, 57xx said:

 

Good point about post-war GWR, my comments are more related to pre-WWII. Having said that I have a 1950 pic that shows a small sprinkling of very light roofs on a train of vans still, so not totally unfeasible.

 

I posted a pic of the railmotor at Didicot showing just that sort of weather on it's roof, heavier at the engine end, very little at the far end. Also check out the clerestory coach at the front of the train in 1929. Surprisingly clean compared with the others! As Martin said, from the pics I have collected, they do seem a lot rarer on coaches though, not totally absent.

 

Westbury1929-2.png.6c58a57f156051f5a5377b7d48b8edd9.png

The weird thing about this photo is that the white-roofed vehicle behind the loco appears to be a clerestory. Surprising that they would do it up at that late stage of its career? Unless my eyes aren’t what they were, and my point would then be pointless!

Link to post
Share on other sites
57 minutes ago, 88D said:

The weird thing about this photo is that the white-roofed vehicle behind the loco appears to be a clerestory. Surprising that they would do it up at that late stage of its career? Unless my eyes aren’t what they were, and my point would then be pointless!

 

Older coaches weren't left to rot. If they were in general service they'd be done up as and when necessary, same as more modern vehicles.

 

In more general terms, the often modelled decrepit branch lines with weeds all over the place and rust-buckets for rolling stock was rarely in evidence until Beeching and the end of steam. Both estate and stock were valuable assets of the railway companies, and taken care of (minor impoverished railways excepted).

  • Like 1
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.