Understanding the quality of your Oil Colour

Oil colour remains the preferred choice of professional painters. Its rich, luscious nature is timeless and irresistible. This month Emma Pearce, former Technical Expert at Winsor & Newton and author of Artist Materials, focuses on how to judge the quality of oil colour, making it easier for you to choose materials to get the best results.

View larger label image here

How wide is the spectrum?

So much of painting is about colour so having the widest possible selection of pigments offers the best choice to artists. Look at the colour chart; is there a good selection of colours in every part of the spectrum?

Artists' Oil Colour Hand Painted Colour Chart

Single or Mixed Pigments?

As with the spectrum choice, different ranges will offer single or mixed pigments. Using the Colour Index Generic Name (see ‘Pigment Content’ on label image) you can see if the colour is made from one or more pigments. Those made from a single pigment will have a unique position in the spectrum and you as the artist can make the choice as to where to take it depending on what you mix with it and how you apply it.  

The single pigments are in a row across the top - use them to go anywhere in the area of the triangle below. If a pigment has already been mixed with another then you are already lower down the triangle with a muddier colour.

However, mixed pigment colours are important and exist for good reasons, such as:

• A pigment has been discontinued and to maintain the brightness and actual colour position of a common colour, eg. Raw Sienna, our Winsor & Newton chemist will have used more than one pigment
  
• Some colours are hugely popular and it saves time to have them ready mixed, eg. Sap Green

What is the Pigment strength?

Judging the strength of a pigment is one of the most important ways of diagnosing the quality of an oil colour. In the lab, this is done by a measured volume reduction with the same white. The highest quality colours have the highest tinting strength. There are also other factors involved:

• Every colour has a different natural strength, eg. Terre Verte is a weak colour
  
• If too much pigment is used there will not be enough oil to coat and carry the pigment particles. These colours will solidify in the tubes
  
• If the grinding of the colour (the dispersion) is not appropriate to each particular pigment then the strength of the colour can be affected. These colours are often less stable, leaking oil and being difficult to handle on the palette

Tinting strength of Dioxazine Purple of Oil colour competitor (Left) and Winsor & Newton Artists' Oil Colour (Right) 

For further information on the pigment strength of Artists’ Oil Colour see the downloadable leaflet.

Compare Masstone and undertone

When a tube is opened what you see when you look inside is the masstone, this is a very dark and strong colour. If the colour is smeared thinly onto a palette you will see the undertone of the colour. The colour comes to life, showing its true hue, brightness, clarity and colour bias. To judge a colour from the tube, make sure you look at the undertone as you will see differences when comparing with different brands and grades of colour. 

Check the Series number

Pigments cost different amounts according to the rarity of the raw material or its difficulty in processing. Pigments also vary in density and oil absorption and so the weight used and therefore the cost is different in every colour. This results in the colours being sold in Series (see label image).
The higher the series number the more expensive the colour.  Don’t confuse this with quality, all Artists' Oil Colours are as highly pigmented as they can be. This mustn't be confused with permanence either. The idea that permanence is affected by series number dates to the time past where cheaper student colours were less permanent - this is not the case now.

What is the type of oil used?

At Winsor & Newton tests show that cold pressed linseed oils have superior properties to alkali refined ones, so oil colours made from the former are better.  With Winsor & Newton tubes the vehicle used (see label image) will be, linseed, safflower or linseed/safflower. This reflects the individual formulation of each colour where our chemist works out which mixture produces the brightest, most stable colour combined with controlling its drying rate and consistency.  In addition, Walnut oil has not been shown to have any superior benefits as it behaves as a mixture of linseed and safflower.

The important time to remember this is when using whites. The whites (except Foundation and Underpainting) are made on safflower to make them brighter and less yellow. If you ordinarily mix white with other colours then they will all dry around the same time. If, however you underpaint extensively with white you must use either Foundation or Underpainting as these linseed oil whites will not cause cracking of subsequent layers. 

There are few oil colour ranges which contain linseed oil whites so a range that does include them demonstrates that it understands the technical necessity of the colour and ensures that an artist can produce the highest quality work.

What is the variable opacity of the range?

Alizarin Crimson over French Ultramarine

The best range of oil colour will show a broad range of opacity (see label image). At Winsor & Newton we broadly categorize all our colour into four bands; Opaque  , Semi-opaque , Transparent  and Semi-transparent . Colours tending towards transparency generally make cleaner, brighter colour mixtures and can be used in layers to produce optical mixing. Colours which are more opaque will cover more easily and give more solidity to images. Look again at the hand painted colour chart above and look at the variety of hues combined with their opacity. there is a huge choice to ensure that you can achieve whatever you want.

What is the Permanence of the colour?

Pigments have become so permanent that this is no longer the issue that it once was. Here again much can be judged by the amount and type of information provided. Winsor & Newton provide permanence rating on all colour ranges (see label image) and these are awarded using results from exposure and acceleration pigment tests in our labs combined with ratings from the pigment supplier.

Additional factors such as pigment strength, chemical stability, humidity, acidity and the effects of varnish are also taken into account. These are the most stringent ratings that exist. ASTM lightfastness ratings can also be used but many of the newer pigments have yet to be tested by ASTM. This is a cost issue and does not imply a negative for a colour which has no rating.

Artists' vs. Students' ranges

Smaller ranges and lower price points will often indicate whether a range is Students’ rather than Artists’. However, it is still worth remembering that any of the elements of a range, such as pigment strength, could still be comparatively good for a student range. It is worth judging the quality of the colour by using the means above rather than relying on the brand name of the paint.

And finally......... Next time you’re painting or choosing a colour, think about the elements discussed. Have you experienced any of these properties at work? Don’t forget they are all interlinked and the best colour involves all these factors. Get to know the Colour Index Generic Names and make the small investment in a Hand Painted Colour Chart; you’ll be able to judge hue and colour bias easily and it never ceases to help with colour mixing.

View all Winsor & Newton Oil Colour ranges