Service Colour / Service Brown

[Casey]

5 hours ago, Steben said:

Can you see this?


The first is an attempt to reduce white, black and blue in the recipe to two colours. That way I could mix the total with 4.
All the rest is simulation of yellowed white (titan buff is a classic) and weight proportions.
Do not forget the ochre in this one is quite yellow instead of orange. We know different ochres tended to be quite less yellow more reddish.

N6 is mixture of Titanium White, Bone Black and Burnt Umber, and so are all N's.

Prussiuan Blue Hue is an mixture of Bone Black, Phthalo Blue (Red Shade), and Dioxazine Purple.

 

This way you actually mix more than 4 pigments using this tool even if not directly.

 

I do not have absorbance/scattering data for lead white, so I cant make much math there. But what can be done is calculating a boundary of colors for those mixes. If you assume the ratios were kept, the variability is in the pigments themselves.

 

Some ideas you may try: If you assume Lead White, Bone Black, Burnt Umber and Prussian Blue (tiny bit to counter the yellowishness of Lead White) are used to mix just some form of N color, your recipe can be further simplified to

 

10x N5 + 8x Yellow Ochre and get similar result to your final mix.

 

Which is not that far off from https://acrylicosvallejo.com/en/product/hobby/model-color-en/german-camouflage-beige-wwii-70821/

 

 

Edited June 4, 2022 by Casey

[Casey]

Ok. I did a little experiment.

 

I've simulated Lead White with an approximate hue of of Titanium White, Titan Buff and Bone Black (77%/22%/1%)

Then I've added the rest of pigments in the proportions from the recipe and came up with (rounding it around a bit)

• 0.400 - Titanium Wh
• 0.115 - Titan Buf
• 0.005 - Bone Blk
• 0.350 - Yellow Ochre
• 0.110 - Burnt Umber
• 0.010 - Carbon Black
• 0.010 - Prussian Blue Hue

The resulting spectral curve looks like:

 

This seems similar to RAL1019 Graubeige...

 

Of course it is all happy weekend theorycraft!

 

 

 

[Steben]

Fantastic.

So slightly more yellow than RAL 1019.

I see you downscaled the white ratio due to the lower weight of titan.

The character of the burnt umber, black and ochre or less tinting white can render easily something like RAL 7008

Edited June 5, 2022 by Steben

[Steben]

[Casey]

7 hours ago, Steben said:

 

My lead-white mixture should be similar to RGH Cremnitz White in linseed (which is PW1, lead carbonate).

 

This is the exact white shade I've aimed for:

 

 

But the main difficulty is that I do not have correct scattering/absorption coefficient data for each wavelength (in other words: how strong this white is). Paints differ in tinting properties, prime example may be bone black vs carbon black.

 

Normally I calculate those values by making tint ladders of paints, but this time I had to go to other sources.

 

I've used this document: "Spectral Behavior of White Pigment Mixtures Using Reflectance, Ultraviolet-Fluorescence Spectroscopy, and Multispectral Imaging" https://hal.archives-ouvertes.fr/hal-01681598/document which has a tint ladder of reflectance curves of lead white mixed with titanium white in different proportions, that helps me to do make some assumptions there (fig4 and 5, page 5)

 

And of course the classic https://www.nga.gov/research/publications/pdf-library/artists-pigments-vol2.html and its lead white section.

 

How confident I would be with this color?

 

Would I paint a model using it: yep.

 

Say it as an exact historical reference? Rather not

 

 

[Steben]

Aside Lead white has a shorter drying time. Not unimportant for non artists in those days. But not important for us.

 

Mixing in drying or boiled oils can colour the paint in a way very close to lead white.

The real pickle is the lower tinting of lead white. And an opacity just below full. I think making an equivalent with less pigment and a bit more coloured oil can do that. But it needs to be zinc or flake hue replacement. 

 

 

[Steben]

https://www.schmincke.de/fileadmin/profitipps-en/PI_11108_Flake_White_hue_EN_151207_web.pdf

This is interesting. "Flake White Hue" (not Flake White!) is a non-lead paint which replicates the properties of lead paints. It is a warm white which is semi-opaque with less tinting power.
And one still needs to reduce its relative volume because of the lower weight.
Alas, the golden mixer online does not have such a gimmick.

Edited June 8, 2022 by Steben

[Steben]

This is the Sherwin Williams pigment recipe for the Liberty Truck in Cantigny.
Alas, I havn't got in touch with a supplier who can mix this in Europe. 

Edited June 11, 2022 by Steben

[Steben]

And these are pictures of the Poelcapelle tank of which I was asked to specify the colour. In different light conditions because it does a LOT. All 4 pictures are the same colour....
It falls completely in the "slightly greener than dark earth / scc2 description".
As you can see it can be fitted with both Female and Male Sponsons...