Colouring technical illustrations

[duncan webster 1Participant @duncanwebster1]

Many years ago old guy (I'm an old guy now!) once told me that before his firm had a copying machine the coloured drawing was on the shop floor under a piece of glass and foremen would make pencil copies of the relevant bits. Sounds like a recipe for cockups to me

[Nigel Graham 2Participant @nigelgraham2]

I think we are in danger of getting too bogged down in technicalities over colours-to-umpteen-decimal-places, or BS standards that might be the BSI type or the other – or simply non-existent.

The original point 100+ years ago was sensibly consistent, tinted drawings to show those you hope will buy your company's products; be they small engines or whacking great railway bridges!

The drawing-office bought its materials from wherever, quite possibly the nearest art stockists; the draughtsman himself (possibly herself, at least as a tracer) mixed the ink or colour wash.

RAL probably stood for anything but paint tints; the nearest "calibration" might have been matching some colour swatches, and the drawing-office optical-wavelength meter was the Eye and Brain, Hominim, Mk.1.

If you want to make your drawings look near those in your prototype manufacturer's catalogue or contract documents, simply go to your nearest art-shop and buy the colours listed in those old text-books; or nearest available now! Oh, and note Jason's instruction on colour-wash technique; and brush up on your pen skills..

If you try it by CAD, do remember to remove the "glue lines" between the generated elements…..

RAL indeed……

++++

Hopper –

Ah, Bevis & Low. Yes, I have a copy, but one of the modern editions: Fifteenth Edition, 1919.

These old books are invaluable references if you are making models of machinery of their time, especially if you don't have full drawings for them.

[HopperParticipant @hopper]

Posted by Nigel Graham 2 on 31/10/2022 22:42:59:…

,,,

Hopper –

Ah, Bevis & Low. Yes, I have a copy, but one of the modern editions: Fifteenth Edition, 1919.

These old books are invaluable references if you are making models of machinery of their time, especially if you don't have full drawings for them.

Yes a weath of information. 1919? That would be modern. The infernal combustion engine was threatening the purity of steam power by then.

It contains some fascinating nuggets. Did you know that flat belt pulleys always run with the drivenpulley up to 3 percent slower than the driver pulley, not because of belt slippage but because the belt on the "tight" side is shorter than the belt on the return "slack" side. And the speed of a pulley is governed by the speed of the belt entering it. So the driver pulley has a longer length of belt to consume in the same time the driven pulley has a shorter length to consume. Ergo, it must run slower. Figure that one out! They have a formula if you need it.

It also carries a treatise on the much debated issue of thin lock nuts on top vs on the bottom. It goes through the explanation, with diagrams, of how the thin nut should go on the bottom so the thick nut on top carries the load, in the modern approved standard manner. Then it says "In practice however, the thin nut is often on the outside because ordinary spanners are too thick act on the thin nut when placed under the other."

So that explains why in pics of old engines, and even in the drawings of such, the position of the thin nut is variously shown both ways. Not because they did not know any better but for practical spanner-access reasons. Those large spanners — say approx. 2" AF and bigger — were expensive and you did not just grind them down to fit. I notice marine engineering drawings, including those for the MOT "ticket" exams, always have the thin nut on top. This would be because then you can pull it apart in the middle of the Atlantic with the standard spanners in the engineers' toolboxes. They do however, have a split pin hole drilled in the end of the bolt/stud to hold the thin nut if it comes loose. ISTR you got an automatic fail if you did not include that split pin hole in your drawings on the MOT exam. I remember one bloke who did that and had to resit the whole (day-long) exam after a suitable period.

Edited By Hopper on 01/11/2022 07:45:23

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Nigel Graham 2 on 31/10/2022 22:42:59:

I think we are in danger of getting too bogged down in technicalities over colours-to-umpteen-decimal-places, or BS standards that might be the BSI type or the other – or simply non-existent.

The original point 100+ years ago was sensibly consistent, tinted drawings […]

.

I am in no such danger, Nigel

… I simply asked a basic question, to which I have had some good answers.

and … although I am always grateful for Jason’s advice, the only bit of his post yesterday that was news to me was that he had a long-running ‘Saturday Job’

MichaelG.

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Edit: __ quoting from my opening post:

The best I have managed to find so-far is this one illustration:

https://wellcomecollection.org/works/e2fk372s

https://wellcomecollection.org/works/e2fk372s

… but six materials doth not a useful standard make

It’s not important … just interesting

Edited By Michael Gilligan on 01/11/2022 08:10:38

[JasonBModerator @jasonb]

Posted by Michael Gilligan on 01/11/2022 08:05:35:

and … although I am always grateful for Jason’s advice, the only bit of his post yesterday that was news to me was that he had a long-running ‘Saturday Job’

I thought you wanted to know if the colours in Hoppers book were still available hence you asking an art suppliers? So would have thought my post confirming the pigments availability was news to you.

These people keep a good range of pure pigment and binders for those that like to mix their own

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 01/11/2022 08:48:34:

Posted by Michael Gilligan on 01/11/2022 08:05:35:

 

and … although I am always grateful for Jason’s advice, the only bit of his post yesterday that was news to me was that he had a long-running ‘Saturday Job’

 

I thought you wanted to know if the colours in Hoppers book were still available hence you asking an art suppliers? So would have thought my post confirming the pigments availability was news to you.

These people keep a good range of pure pigment and binders for those that like to mix their own

.

Let’s not get into ‘violent agreement’ Jason

As you so rightly stated:

“most of those colours are still available with the exception of a few who's pigments have been found to be toxic. There are also a few substitutes where cost or availability put some pigments out of reach.”

… and it is the exceptions and substitutes that prompted my question to the supplier.

MichaelG.

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Edit: __ as an example :

after the trauma of seeing that alleged ‘Paint Swatch’ of Gamboge [referenced earlier], I then found this  

https://www.winsornewton.com/uk/?s=new+gamboge

and wondered how and why it differed from real Gamboge

Edited By Michael Gilligan on 01/11/2022 09:10:56

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Michael Gilligan on 31/10/2022 11:12:50:

Posted by Neil Wyatt on 31/10/2022 10:09:35:

The color gamboge …

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… is also described here: **LINK**

https://www.theawl.com/2017/11/gamboge-a-sunny-yellow-with-a-deadly-past/

With a highly suspect ‘painted swatch’

MichaelG.

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Re-posted for convenient reference ^^^
.. because the Gamboge pigment features significantly in the ‘recipes’

MichaelG.

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Edit: __ and here is a direct link to the ColourLex page

https://colourlex.com/project/gamboge/

Edited By Michael Gilligan on 01/11/2022 09:27:47

[JasonBModerator @jasonb]

I used to have access to all the charts that gave the chemical composition of the alternatives but can't remember what the makeup of new gambouge was.

However the more specialist outlets such as the one I linked to do still sell the natural pigment from the tree here

[Michael GilliganParticipant @michaelgilligan61133]

The Gamboge issue continues to fascinate me … [but perhaps not anyone else]

**LINK**

https://www.cornelissen.com/gamboge-powder.html?___SID=S

Given the nature of the natural pigment ^^^, and the timeline of the introduction of synthetics:

To which substance do the quoted ‘recipes’ for Brass and Copper colours refer ?

Does it matter ? … probably not

All we I really want is a reasonable indication of what the 19th Century illustrators were aiming for.

Reminder: The link I first posted only features six materials.

MichaelG.

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Edit: __ my post just crossed with yours, Jason

… incidentally; did you watch the video on the ColourLex page ?

Edited By Michael Gilligan on 01/11/2022 12:35:55

[JasonBModerator @jasonb]

half before lunch called

[Mick B1Participant @mickb1]

Coloured technical drawings certainly reached a high standard in WW1:-

[Nigel Graham 2Participant @nigelgraham2]

Rather more peacefully, most of the diagrams in BR / BTC manual for steam-locomotive drivers and fireman are coloured to represent the working fluid in each part of that system: steam, water, air, or mixtures.

[Michael GilliganParticipant @michaelgilligan61133]

One small step [and all that] …

The nice lady at Ken Bromley Art Supplies suggested the Windsor & Newton site, which I had seen, and this one which I had not: **LINK**
https://danielsmith.com/wp-content/uploads/2021/04/full-266-watercolor-chart-oct2022.jpg

That’s a rather impressive chart, which I shall be digitally sampling for my further education

Presumably his ‘Indian Yellow’ is effectively ‘Gamboge’

MichaelG.

[Dr_GMJNParticipant @dr_gmjn]

This is a great book for coloured drawing/schematic enthusiasts:

[SillyOldDufferModerator @sillyoldduffer]

Posted by Michael Gilligan on 02/11/2022 18:10:58:…

Presumably his ‘Indian Yellow’ is effectively ‘Gamboge’

MichaelG.

Close, but not identical. Indian Yellow is #E3A857 and Gamboge is #E49B0F. I can just tell the difference on my laptop screen. This website seems quite comprehensive as a way of finding the RGB values of colour names.

They're both about the colour of normal urine!

Dave

[Michael GilliganParticipant @michaelgilligan61133]

Posted by SillyOldDuffer on 02/11/2022 22:08:35:

Posted by Michael Gilligan on 02/11/2022 18:10:58:…

Presumably his ‘Indian Yellow’ is effectively ‘Gamboge’

MichaelG.

Close, but not identical. Indian Yellow is #E3A857 and Gamboge is #E49B0F. I can just tell the difference on my laptop screen. This website seems quite comprehensive as a way of finding the RGB values of colour names.

They're both about the colour of normal urine!

Dave

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That’s only the ‘Gamboge’ that you have chosen as being definitive, Dave

Please see my earlier post, and particularly the video demonstration that is on the ColourLex page.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Silly me

He has ‘New Gamboge’ on there as well as ‘Indian Yellow’

MichaelG.

.

[JasonBModerator @jasonb]

Most of the makers do two colour charts, one printed which is quite well colour matched and then the expensive chart which is made up of individual pieces of water colour paper with a graduated wash of each colour and these are obviously the best guide to what may come out the tube of off the block. Once you add in screen and scanner variations you get further from the true colour.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for mentioning it, but

I don’t anticipate buying the ‘Analogue’ version of that chart, Jason

Eventually, they say: Curiosity killed the Cat

and I’m happy to keep this quest for knowledge at level I can comprehend and afford.

MichaelG.

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FootNote:

For anyone who wants to join me in that quest: Here is a crop of the ‘New Gamboge’ from that chart, with the worst of the jpeg artefacts at the edges omitted.

N.B. This will be a lamentably poor approximation of the real thing, but we can now set-to with the digital toys.

.

 

Edited By Michael Gilligan on 03/11/2022 09:39:57

[SillyOldDufferModerator @sillyoldduffer]

Posted by Michael Gilligan on 03/11/2022 09:24:27:

… I’m happy to keep this quest for knowledge at level I can comprehend and afford.

MichaelG.

It's already got too complicated for me! The RGB system is an excellent way of defining colours numerically, but it runs smack into the buffers when trying to predict the result of mixing two known colours. Mixing Blue and Yellow produces Green in our heads, but adding RGB values doesn't. It seems there isn't a simple algorithm for mixing RGB color codes and getting the expected result.

So. colouring with a computer, I don't know of an easy way of calculating the colour of Brass – 'Gamboge with a little Red'. No bother with a kiddy paintbox but I can't program it. Doesn't matter if the colouring is done with paint on paper, but it's much easier for a cack-handed brute like me to colour digital images with software.

Dave

[Michael GilliganParticipant @michaelgilligan61133]

Here’s a starter:

[Michael GilliganParticipant @michaelgilligan61133]

Posted by SillyOldDuffer on 03/11/2022 09:51:09:

Posted by Michael Gilligan on 03/11/2022 09:24:27:

… I’m happy to keep this quest for knowledge at level I can comprehend and afford.

MichaelG.

 

It's already got too complicated for me! The RGB system is an excellent way of defining colours numerically, but it runs smack into the buffers when trying to predict the result of mixing two known colours. Mixing Blue and Yellow produces Green in our heads, but adding RGB values doesn't. It seems there isn't a simple algorithm for mixing RGB color codes and getting the expected result.

So. colouring with a computer, I don't know of an easy way of calculating the colour of Brass – 'Gamboge with a little Red'. No bother with a kiddy paintbox but I can't program it. Doesn't matter if the colouring is done with paint on paper, but it's much easier for a cack-handed brute like me to colour digital images with software.

Dave

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Dave,

I have an assortment of Apps which look very promising

Having worked at KODAK in the 1970s … whilst I am certainly no expert, the general subject of colour reproduction fascinates me and I suppose this thread was prompted by that.

Happy to continue here, or off-forum if everyone else is bored already.

MichaelG.

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Edit: __ 1931 was probably the year that practical things started to get technical:

 

Edited By Michael Gilligan on 03/11/2022 10:14:03

[JasonBModerator @jasonb]

I just gave it a try in Alibre, although I can enter the RGB values which I took from Dave's earlier link that gives a very solid colour much like it would come out of the tube.

However once I move the slider to get a lighter "wash" the RGB values change so is it still Gamboge?

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 03/11/2022 10:13:31:

I just gave it a try in Alibre, although I can enter the RGB values which I took from Dave's earlier link that gives a very solid colour much like it would come out of the tube.

However once I move the slider to get a lighter "wash" the RGB values change so is it still Gamboge?

.

The lighter “wash” should simply be the result of all three values changing in the same proportion.

So, Yes [within the bounds of what the bit-depth can handle] you still have the same colour

Does Alibre mention what ‘Colour Space’ it uses ?

MichaelG.

Edited By Michael Gilligan on 03/11/2022 10:44:20

[Michael GilliganParticipant @michaelgilligan61133]

This is the output from an App which analyses the content of an image, and shows all the colours used within it:

.

Plugging any of those numbers into Alibre, or whatever, should produce the same colour as the adjacent patch.

Remembering of course, that what you see on your screen will inevitably differ from what I see on mine.

MichaelG.

[Author]

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