What do the numbers in the Details and Descriptions of Individual Colours mean?

Details and Descriptions of Colours

The individual colour descriptions provide assessments for certain determinable characteristics of all the colours presently in the Michael Harding Artist Oil Colours range as well as a few informal remarks by Michael on their qualities and idiosyncrasies when used.

The Colour Index Number:

This is the international system for classifying and identifying pigments by their (some times complex) chemical formulae (e.g. P(igment) R(ed) is expressed as Pr 106, Mercuric Sulphide known as Genuine Vermilion). The use of vague traditional or invented colour names is thus clarified and so in theory at least is the vexed matter of what pigment manufacturers actually put into their paints. If a colourman is honest, each constituent pigment in a paint can be specified precisely, and the practice of secretly adulterating or even completely substituting cheaper alternatives is made impossible. Assuming, that is, the colourman is honest . . . I can certainly state that there are no secret additions to any of the paints in my range. What you read as the C.I. number on the label is what you get.

Estimated Drying Speed:

Keep in mind that all drying speeds are affected by: temperature, humidity and light levels. The aforementioned conditions provide for a broad calibration of comparative speeds from: Very Fast, such as the Umbers, many of which if used neat (unmixed with other colours), will be touch dry within a warm summer day, to the Very Slow, which in an unmixed state, might take up to a week to cure. This is governed by how thickness of the paint layer. Please remember the thicker the layer the longer it will take to cure.


This gives some indication of the resistance of a pigment to fading when exposed to very high light levels. Though the commonly used numerical system for this is the scale devised by the American Society of Testing and Manufactures (ASTM I-V), in practice the fade resistance of pigments is greatly affected by their concentration, or lack of it, in paint mixes. Thus an excellent lightfast pigment (ASTM I), if dispersed in a paint by the addition of fillers will in consequence show increased tendency to fade. As I have said before, there are no fillers added to the pigments in my oil paint range.

Tint Power and Transparency:

This characterizes the ability of a given paint to cover over the substrate onto which it is painted. Cadmiums are the most opaque and Indian Yellows are the least opaque. Transparency should not be confused with sheer strength of colour or Tint Power as it is revealed in mixes. Some transparent paints, e.g. the Phthalo Lakes, are ferociously strong when mixed with sturdily opaque hues.

Oil Content:

This indicates broadly how much oil has to be ground in with the dry pigment or the lake dye in order to make it into a workable paint. Paint with high oil content will generally, but with exceptions, dry to a glossier surface and that with low oil content will be leaner and tends to be less glossy.


This subject must be taken seriously if you want a long and healthy relationship with oil paints.
More advice is given in the Health and Safety section of the Michael Harding website.


All Michael Harding Artist Oil Colours conform to ASTM D-4236 (always read the label).

19 Responses to “What do the numbers in the Details and Descriptions of Individual Colours mean?”

May 28, 2017 at 10:44 pm, Melissa O'Faherty said:

Hello, just seeing if you have a handpainted colour chart and if i could purchase one?


December 07, 2017 at 1:11 pm, Joelle Harding said:

Hi Melissa,

You are able to purchase a hand painted colour chart from any of our suppliers! 🙂


May 17, 2018 at 5:41 pm, Susan Ertelt said:

Thank you for your beautiful paints Micael!! They are a joy to see let alone paint with. Thank you!!. I would love a paint chart for reference. Please let me know where I can pick one up. I’m in Massachusetts and Connecticut, so I may need two. Cheers. Susan♡


May 24, 2018 at 10:20 am, Michael said:

Hi Susan,

Thanks for your lovely comment! They are a joke to make, and a joy to see artists use and adore!

You are able to download as many colour charts as you like using the link below, however, if you want an actual colour chart then I would advise heading to your closest MH Retailer (you can find them using the “where to buy” page).

– Link to colour chart : http://www.michaelharding.co.uk/resources/michael-hardings-paint-colour-brochure-for-you-to-download/
– Link to where to buy : http://www.michaelharding.co.uk/where-to-buy/

Happy painting!


January 12, 2019 at 12:45 pm, maggie said:

I want to buy a white that mixes well with other colours yet doesn’t taint the colour.
Please recommend one.
thank you


January 30, 2019 at 3:47 pm, Michael said:

Hi Maggie!

Titanium White sounds like it will do the trick for you.

Please feel free to visit the link below and click on the different Colour Swatches. They will open up with more info about each Titanium White:

Best Wishes!


November 26, 2019 at 2:13 pm, Hadrian Richards said:

Could you please clarify the oil colours known as dyes. Are lakes the same as dye colours or is there a difference?


December 04, 2019 at 1:52 pm, Michael said:

A dye is a chemical that shows colour when it is dissolved. Dyes can be bought in a granular version and a dusty light powder form.
A lake pigment is a pigment made by precipitating a dye with an inert binder, or “mordant”, usually a metallic salt. Unlike vermilion, ultramarine, and other pigments made from ground minerals, lake pigments are organic.


December 29, 2019 at 7:51 pm, Wendy said:

Will you be removing the zinc white from your warm white as well?


February 20, 2020 at 3:51 pm, Michael said:

Any of my paints containing Zinc are being reformulated and phased out 🙂


January 07, 2020 at 11:57 am, Liz said:

What would you recommend closest to a Chrome yellow


February 17, 2020 at 4:54 pm, Michael said:

Hi Liz,

Any of the following:

Cadmium Yellow – Opaque, semi-transparent if painted very thinly.

Yellow Lake – Transparent

Bright Yellow Lake – Transparent


March 23, 2020 at 7:03 am, Rob said:

Hi Michael, I’ve recently read that all red cadmiums have PW21 in any manufacturers. Is that true? Do your cadmiums red have It? What proportions? Thanks


April 06, 2020 at 12:19 pm, Michael said:

Hi, I list all of my pigments on the label and also on the product page.
Here is more information on all of my Cadmium Reds:




If it is not on the tube then it is not in the paint! 🙂


May 27, 2020 at 3:08 pm, Amanda said:

what is the best vermillion replacement?


June 09, 2020 at 4:37 pm, Michael said:

Cadmium Red

Best Wishes,


January 04, 2021 at 7:06 pm, Igor said:

Why in your line there is no cobalt blue deep under the index p.b.74 ?


January 26, 2021 at 5:33 pm, Michael said:

Cobalt Blue made using PB74 is from another brand. For my Cobalt Blue, please follow – https://www.michaelharding.co.uk/colour/cobalt-blue/

Or for all of my Blues please follow – https://www.michaelharding.co.uk/oil-colours/?tc=25


January 06, 2021 at 9:15 pm, Steb said:

Just started using your paints a few months ago, amazing paints and that oleo gel, wow unbelievable stuff, and it knocks the socks of your competitors ( I use that term loosely)


Leave a Reply to Susan Ertelt Cancel reply

Your email address will not be published.