Painting & drawing blog
HOW TO READ A PAINT TUBE
The anatomy of a label
I have to admit that when I first starting buying paints as an art student, I chose them solely based on the appearance of the colour swatch printed on the label. I really didn’t know anything about how paints were manufactured and the only other decision I’d make when buying a tube was to avoid the most expensive shades, since paints of all types vary wildly in price depending on the pigments they contain. Since becoming a professional artist however I have learnt how to read all those mysterious labels and codes that you find on the label of a paint tube. I’ve found that doing so taught me a great deal of vital information about how to choose and apply my colours more effectively to give long term stability to my work. It was also an interesting insight into how paints are marketed to us as consumers.
Here we are going to explain all those mysterious marking on label on a tube of oil paint, but whether you paint in oils, acrylic or watercolour you’ll find these explanations will still apply just the same. The only markings I’m not going to discuss here are the self-evident quantity information (given here in both mililitres and fluid oz) and a few tiny little printed numbers such as the ‘0430’ printed on the bottom of this tube. These are identifying marks for the paint type and colour designed for the company that makes them to understand. They aren’t supposed to be understood by the consumer.
1) MARKETING NAME
You might think that this is so self-evident that it requires little discussion. However the name that the paint manufacturer gives to their product is likely to be the most misleading piece of information on the label! I call it the ‘marketing’ name because that’s really all it is: a name plucked out of the air which doesn’t conform to any kind of standardized or universal scheme.
It’s important to distinguish here between the marketing name of the paint chosen by the manufacturer, and the official name of the ground up pigments(s) that it actually contains. To understand this we need to be aware of the difference between the terms ‘paint’ and ‘pigment’. The pigment is what gives the paint its colour and derives from a ground up organic substance, or a chemical, synthetic substance. The paint is the combination of the pigment or pigments, a binder (such as oil, acrylic polymer or gum arabic) which binds the paint together and dries into a film when applied) and any other additives which may be included, such as drying agents. The ONLY way to tell which actual pigment is the tube is to look for the ‘Colour Index Name’ on the back of the tube. This is something which we will cover below.
You will commonly find that two different companies may both produce a paint colour with the same marketing name but made from different pigments and which have slightly different shades. In fact, even paints made by the same manufacturer may utilize different pigments to make the same ‘colour’, depending on the medium. For example whilst our Winsor and Newton tube of ‘Pthalo Turquoise’ oil paint in the picture contain one particular combination of pigments (a blue and a green) mixed to make a turquoise, their tube of ‘Pthalo Turquoise’ watercolour actually contains a single, turquoise-coloured pigment. The bottom line is this is that if you really want to know what colour is inside the tube you need to open the lid and take a look! However, if you still aren’t clear which pigment you are seeing you won’t be able to understand what kind of properties it will have and how it will affect your painting.
How do companies choose their colour names? In an ideal world the marketing name would match the name of the pigment, so that a ‘cobalt blue’ – for example – would contain only cobalt blue pigment. However when the shade in question is a mixture created to create a colour that doesn’t exist as a pure pigment (something like a ‘sap green’ for example) then different manufacturers will use different pigments to achieve the shade they want.
In other cases a paint colour may be derived from a single pigment but when that pigment is a synthetic one with an name that doesn’t exactly trip off the tongue, then the manufacturer will often come up with a more catchy one. Pthalocyanine Green pigment for example is variously marketed as ‘Sap Green’, ‘Rembrandt Green’, ‘Phtalo Green’, ‘Winsor Green’ or ‘Zulu Green’ to name but a few.
Manufacturers will also come up with romantic but technically meaningless names such as ‘Old Delft Blue’, or generically descriptive names like ‘Brilliant Orange’, or will continue to market paints with the names of pigments which are no longer used due to toxicity, lightfastness problems or other reasons (for example Van Dyke Brown, Rose Madder and Naples Yellow). When they do this they are supposed to add the word ‘hue’ at the end of the description. This is an important term to learn: a ‘hue’ paint is mixture of pigments combined to match a single-pigment colour.
Sometimes hues are created just to provide a cheaper alternative to a pure, single-pigment colour that’s expensive to produce. Hue paints are therefore very helpful to the beginner as they may cost only a fraction of the paint that is being matched. For example, ‘Cadmium Red Hue’ is a combination of pigments selected to closely match genuine Cadmium Red – an expensive pigment which is made from Cadmium Sulfoselenide – but contains no actual Cadmium. Cadmium Hue is made up of three different pigments and costs less than half the price of true Cadmium. However because hue paints generally give a rather muddier tone when mixed and may offer less lightfastness (they may not always match the original pigment in terms of their permanence, or other properties and can either improve upon the properties of the original colour or compare unfavourably) the fact that they are a hue should be declared.
2) PERMANENCE RATING
Our tube of paint has been given a ‘permanence rating’ of ‘A’. There’s no universal standard in permanence ratings and each company rates their paint according to their own scheme. Winsor and Newton’s letter rating system is as follows:
AA – Extremely Permanent
A – Permanent
B – Moderately Durable
C – Fugitive
Daler-Rowney paints use a ‘star’ rating system for permanence. Other brands (such as Royal Talens) may omit a ‘permanence’ rating and instead simply give a rating for ‘lightfastness’.
These two terms – permanence and lightfastness – are confusing as they are often used more or less interchangeably. Strictly speaking ‘permanence’ is usually defined as the pigment’s resistance to exposure not only to light but also to various atmospheric conditions and to other factors such as the stability of the binder and the durability of the paint over time. These may include how the pigments behave if used in a thin glaze or if they are combined with a white, and how they behave when mixed with other pigments. Winsor & Newton defines permanence as classifying “not only lightfastness but also film & chemical stability of the paint”. However this doesn’t stop them from also giving a separate ‘lightfastness’ rating on the back of the label, as we’ll discuss below.
3) SERIES NUMBER
The last piece of coded information we are given on the front of the label is the ‘Series’ number. This is your shorthand clue as to how expensive the colour is likely to be, before you’ve consulted the price list. Manufacturers generally group their colours into five different price brackets or ‘series’. Series 1 paints will be made from the cheapest pigments and will be the least expensive in the range. Hue colours and many modern synthetic colours will be found in this band. Series 5 paints are the most expensive and can cost well over twice as much as those in the Series 1 bracket. They are more likely to be derived from single pigments which are difficult and costly to produce.
Let’s now take a look at the back of the tube:
4) COLOUR INDEX NAME/NUMBER
Turning over the tube we finally find the only really useful information about what’s actually inside it. This paint is listed as containing pigments ‘PG7 and PB15’. This information relates to the ‘Colour Index’ which is a standardized naming system regulated jointly by the British-based Society of Dyers and Colourists and the American Association of Textile Chemists and Colorists. You can find a useful version of this database for free here although for access to the official list you’ll need to pay a subscription.
The Colour Index name is actually both an officially assigned name, and a code. The code is comprised of two letters and a number. The first letter will always be a P which denotes that it’s a pigment (rather than a dye, for example) and then there will be another letter denoting the colour category: R for a red, O for an orange, Y for a yellow, G for a green, B for a blue, V for a violet, Br for a brown, W for a white, Bk for a black and M for a metallic pigment. Lastly there will a number which defines the individual pigment within that colour category, according to the list. Our paint tube includes two pigments – a PG colour which is a green (in this case a number 7 green which indicates the pigment Phthalocyanine Green BS) and a PB colour which is a blue (number 15, which indicates the presence of Phthalocyanine Blue)
You may notice that this particular tube of paint doesn’t follow best practice and omits to list the official names of the pigments, giving only the index code. This is more common on European-manufactured tubes than American ones and it’s frustrating since we can’t be expected to easily identify an index number without looking it up on the database.
The index name/numbering system still isn’t a completely reliable guide to the colour in your paint tube since the actual shade of the pigment may vary between paint makers depending on their manufacturing processes, even if the pigments are chemically equivalent. However it’s the most accurate way to identify which colour you are actually buying.
5) PAINT VEHICLE
The ‘vehicle’ really means the ‘binder’, or the medium that’s been mixed with the pigment. It’s the substance that has been added to the pigment to bind it together and allow it to form a film that holds it in place on your canvas or paper when it dries. Since our tube is a tube of oil paint, the medium used is an oil – in this case, linseed oil. In acrylic paints the pigment is suspended in an acrylic polymer emulsion whilst in watercolour paints the binder used to be Gum Arabic but is now sometimes Synthetic Glycol. The ‘vehicle’ technically also includes any dilutants which may be added if the binder used is too thick.
6) LIGHTFASTNESS RATING
Winsor and Newton use a system of ratings between I and III to indicate how likely their paints are to fade with prolonged exposure to the light. They say that “In this system I is the highest lightfastness available, though both ratings I and II are considered permanent for artists’ use.” This conforms to standards laid down by the ASTM (American Society for Testing and Materials) standard which rates the general performance of art materials, including a pigment’s lightfastness which is rated on a scale from I (the most lightfast) through to V, the least lightfast.
Royal Talens use a system of little crosses to denote lightfastness. The crosses’ represent: “the expected permanency of the pigment and how long it can be expected to withstand light exposure without fading”. According to their system: “+++ indicates 100 years lightfastness under museum conditions (the highest degree of lightfastness) whereas ++ means 25-100 years (what the company calls ‘normal lightfastness”.
How far can we trust the lightfastness information given on a label? It’s important to be fairly sceptical here and to realize that lightfastness isn’t a fixed and easily measurable thing, is not constant over time, and that therefore these ratings can be quite misleading. The lightfastness of a paint depends on number of different factors and in particular on the manufacturing methods employed both in making the pigment, and then in creating a finished paint from the pigment. This particularly applies to synthetic pigments. Besides, if the guarantee of permanence is dependent on museum conditions then it’s not terribly applicable to the way most of us display a painting within our homes. In a home environment that isn’t perfectly controlled for sources of light, paints may fade a lot faster. Lightfast guarantees for some watercolour paints for example may be based on the premise that like in a museum, we will display them only for a few months at a time and then keep them in a dark drawer!
No paint tube tells us exactly what has been measured: for example it’s never made clear whether it’s the finished paint that has been tested, or just the original pigment. This is important because the lightfastness of a pigment can vary depending on the medium. For instance Vermilion pigment has a top rating of ‘I’ when used in oils and acrylics. With watercolour however it has a rating of ‘III’ which is merely fair. If a paint company displays the ASTM seal (more on this below) it may be unclear whether this means they haven’t tested the paint themselves. If they have relied on an ASTM test for a generic pigment, how long ago was the test carried out and is it reliable? We can play it safe by selecting paints given the highest rating and I’d certainly advise avoiding those with a ‘fugitive’ rating at all costs. However the only way to really show how lightfast a paint is is to paint some samples, sit them by a window and wait to see what happens as the months go by.
This is an indication of the degree of transparency of the paint, shown here by the little empty/white box . This indicates that the colour is very transparent. A white box with a diagonal line through it means semi-transparent, a diagonally-divided half-white half-black box indicates semi-opaque, and a completely black box would mean it was totally opaque.
Manufacturers find a variety of ways to indicate the degree of transparency/opacity. Sometimes a little ‘wheel’ icon is used. Other products employ a lettering system whereby transparent colours are marked ‘T’ and semi-transparent as ‘ST’, whilst opaque colours are marked ‘O’ and semi-opaque ‘SO’. Other manufacturers will keep things simple and just write ‘Opaque’, ‘Semi-Opaque’ and so on.
8) ASTM STANDARD CONFORMITY
Although our paint tube was manufactured by a British company, most European paints will indicate their compliance with American standards for paint labeling as regards health and safety. These codes are voluntary but have been widely adopted. This seal indicates that the paint conforms to the American Society for Testing and Materials’ ‘ASTM D 4236’ which is their ‘Standard Practice for labeling Art Materials for Chronic Health Hazards’ set of guidelines. Inside will be either a large ‘AP’ (Approved Product’) or ‘CL’ (Cautionary Labeling). If there’s a CL label then in the tube will also contain a specific written warning about problems posed by the pigments the paint contains.
This code of conduct requires the Pigment Index Number to be displayed on the label, amongst other display requirements including the declaration of any potential health hazards from the pigments contained within. In practice toxic pigments (containing lead, strontium or mercury, and to an extent heavy metals such as nickel) are rarely now used due to both prevailing common sense, and to governmental/ state/ EU legislation. You can read more on pigment safety here.
9) ACMI NON-TOXICITY SEAL
The Art & Creative Materials Institute, Inc. or ‘ACMI’ is an American non-profit association of art and craft supplies. An ACMI Approved Product Seal on a paint label certifies that the paint is non-toxic both children and adults and “contain no materials in sufficient quantities to be toxic or injurious to humans, including children, or to cause acute or chronic health problems”.