Getting to the bottom of how pigments (and indeed different preparations thereof) behave ultimately can become a bit of a rabbit hole. I will aim in this post to wander, perhaps cicuitously, through some of my thoughts and considerations when exploring and using different pigments in different ways.
Classifying pigments
On a very basic level, in my mind there are essentially four different types of classifying pigments. These are Natural Organic, Natural Inorganic, Synthetic Organic, and Synthetic Inorganic.
Natural Organic Pigments
are those made from plant or animal origin – though instantly the waters can be muddied to an extent as many of these are dyes and are laked (chemically bonded) to an inorganic precipitant (often aluminium hydroxide)1. Examples of these could be madder root, cochineal, indigo, Tyrian Purple, stil-de-grain (buckthorn berries). Other pigments may simply be ground plant or animal material – dragon’s blood resin, gamboge, charcoal, burned bones, peat, and (the favourite) asphatum from mummies…
Natural Inorganic Pigments
are metal or rocks which occur naturally, often metal oxides, oxide hydroxides, sulfides, sulfates, silicates and carbonates. This includes red, yellow and brown earths (iron oxides), green earths (clays containing large amounts of silica and the green minerals), slate, chalk, and coloured minerals such as lapis lazuli, cinnabar, malachite and so on. Virtually any coloured rock can become a pigment if it is ground finely enough.
Synthetic Inorganic Pigments
cover a wide range of compounds, from historical copper compounds such as bice, verditer, and verdigris, synthetic iron oxides made under controlled conditions, ranging through cobalts, cadmiums, prussian blue, french ultramarine (chemically identical to lapis) right through to complex modern pigments like the Siccopal pigments and YInMn Blue.
Synthetic Organic Pigments
are those based on organic compounds in chemcial terms (though a small subset may have other atoms like metals in their structure). These are often derived from petroleum products and tend to have wonderfully complex sounding names – arylide, diarylide, disazo condensation, perylene, isoindolinone, phthalocyanine, quinacridone, diketo-pyrrolo pyrrole, dioxazine and so on.
These catagories can go some way to help us to understand the artistic properties and uses of various pigments, but first, before we explore these further it is useful to think about pigments as catagorised by some of these properties, which can again be done in several different ways.
Transparent/Opaque/Staining/Granulating…
Perhaps the most basic catagorisations of pigments (or, to be more totally accurate paints as sometimes the way a particular preparation is made can change this) could be argued to two binaries of Transparent/Opaque and Staining/Granulation, and this is indeed often given as basic infomation by manufacturers2. For basic understanding of how a paint will behave, these are a good start, but instantly run into issues, for example some colours may be very opaque if you could apply them in sufficient mass-tone, but act to all extents as transparent in use (Smalt springs to mind) due to how they wash out and often granulate. Others may stain but still granulate – or at least are flocculating and sedimentary (some cadmiums). Others are classically seen as staining, and stain they do, but flocculate strongly due to hydrophobic properties in certain preparations (Phthalo Blue). To move further on from this there needs to be more nuance.
Kosavic – The Transparent Watercolour Wheel
These defintions of pigments as “Transparent”, “Opaque”, Staining, Granulating and so on have basic meanings which as we have discussed above, and in this sense do not take too much to understand, but they have a specific meaning in Jim Kosavic’s Book “The Transparent Watercolour Wheel”3 where he expands these to a set of specific qualities with general advice on how they react together in mixes and glazes.
These are as follows:
Transparent Non-Staining
As they suggest, these are colours with some level of transparency, which do not stain the paper and can be lifted to leave limited trace.
The key colours Kosovic lists here are: Rose madder Genuine (NR9)4, Permanent Rose (PR605), Cobalt Blue (PB28, also likely PB72, PB73 and PB74 which are other Cobalt Blue Pigments), Veridian (PG17), Hookers Green6, Aureolin (PY40).
In general they share similar handling characteristics – they will mix well with one another and you can generally mix more than two without getting to too muddy. Mixing with Opaque colours can clean up the opaques. Mixing with stains can be very effective, but can dye the transparent non staining colours and totally change the effect. Generally, they have a weak tinting strength and are light valued, making dark mixes difficult.
Semi-Transparent Non Staining
Reading on, you will note that there’s quite some cross over between the granulating pigments (discussed later) and the transparent non-staining and the transparency is to an extent created by the tendancy to granulate rather than cover thickly and smoothly. The Semi-Transparent Non-Staining colours are deeper, and a little more intense.
Kosovic Lists the following: New Gamboge7, Raw Sienna (PBr7), Quinacridone Gold (PO49)8, Quinacridone Burnt Orange (PO48), Burnt Sienna (PBr7), Vermillion9, Quinacridone Burnt Scarlett (PR206), Permanent Magenta10, Opera (Often PV19, with PR81/flouro), Permanent Mauve (Manganese Violet, PV15?), Prussian Blue/Antwerp Blue (PB27), Cyanine Blue11, Sap Green12, Green Gold (PY129).
Can be glazed without worrying abut mud, but care needed to avoid lifting. Mixing with Opaque colours can clean up the opaques. Mixing with stains can be very effective, but can dye the transparent non staining colours and totally change the effect. These tend to have darker values and higher tinting strengh than the transparent non-staining pigments.
Transparent Staining
These are colours that stain the fibres of the paper, that are brash, intense, saturated. Kosovic13 himself points out that the pigments used in these may well be very opaque in mass tone, but in use they are colours that would tend to be diluted and used in a wash. These are the Winsors14, and similar from other brands, essentially most modern organic pigments such as Arylides, Phthalocyanines, Napthols, Dioxazine Violet, Indanthrone Blue and so on.15 Kosovic includes Hookers Green light – perhaps meaning the Nitroso green, Carmine – uncertain if he means natural carmine – and Alizarin in this section. I would add some organo-metal compounds (Nickel and Copper Azomethines), Pyrrols, Pyrazolones, and Perylenes etc.
These can easily take over mixes, work well as glazes and are resistant to lifting. They will often flow into heavier colours – but this is to an extent affected by preparation.
Interestingly, Kosovic does not mention the Quinacridones here at all. We’ll discuss them later, in any case.
Semiopaque and Opaque
Kosovic lumps together a number of colours here – though what is important is that he notes that the usage of these is often transparent. He includes here: Cadmiums, Hansa Yellow (something which which I would not agree), some Quinacridones, Cobalts and Ceruleans, Manganese Blue, Bice, Ultramarine. I would add Nickel Titanate, Nickel Dioxine and some of the more modern compounds – YInMn Blue, Siccopal Pigments, Bismuth Vanadates and so on.
Kosovic notes that these will often mix ok with one other of their own type, and with transparent non-staining, but very quickly become muddy.
I will leave this section here, as I am going to expand somewhat on these shortly.
Whitened and Blackened Colours
Kosovic16 refers to these as “semiopaque and opaque colours which have some black or white in their composition”, which reads to me to sound like he is seeing many of these as mixes – however many of these are obviously single pigments. It is perhaps better to think of earths, blacks and whites. Kosovic lists Naples Yellow (most likely thinking of a blend), Ochres, Umbers, Sepia, Indigo, Terre Vert, Mars Violet, Blacks, Whites and Tints, but also Hookers Green Dark (mentioned elsewhere) andf Perylene Maroon (which I would class firmly a as a transparent stain.
In use, he suggests these are broadly the same as Semi-Opaques and Opaques, which for now I will leave as it is.
What is clear here is many of these are granulating or sedimentary, yet granulation is not restricted to these, some can stain, and not all follow a neat definition.
We need to go further.
Keene Wilson
Keene Wilson17 reherses and expands a little on the work of Kosovic, widening the discussion on the (semi)opaques.
He breaks down these into a few diffent catagorsiations, looking at “intense” opaques (in which he lists Cadmiums, Ultramarine, Mineral (Manganese) Violet, Cerulean, Manganese Blue, Hansa Yellow and Quinacridone Violet with the notes that two will mix, but must not be messed with, and echoes Kosvic that more than two will make mud, they mix nicely with transparent non-staining, but will be very dull when mixed with stains.,
He makes a special note on the Cadmiums that while these are some of the most intense colours (from opaques) they can be chalky and work in many ways better when pulled out, and do not like mixing with anything other than cadmiums.
He makes specific notes about some of the others, for example avoiding re-stating Cerulean, that Ultramarine does not mix well with various other opaques and so on. He also notes that Tom Hill (as so I) considers Hansa Yellow a transparent.
This breaks some of the outliers slightly out of Kosovic’s assessment.
Where this is important is that it begins to make the distinction between granulation and sedimentary colours – while similar they are distinct characteristics. Moving on one also needs to consider flocculation18. For me, at least, Cadmiums, Mars Violet (Caput Mortuum), Oxide of Chromium (to name a few) are better described as sedimentary than granulating. Qinacridones and some other organics are granulating, but the particle sizes are small enough this is very different than what we would consider true granulation. Cobalts, which Kosovic lists as transparent, are very granular. And Phthalocyanines flocculate very strongly, mimicking granulation due to their hydrophobic properties, and yet the preparations they are released in often have specific additives to prevent this.
Enter the Quinacridones!
I hope that Caroline Buchanan will forgive the minor plagairism of a subheading in her great article for Daniel Smith, Making Sense of Staining, Sedimentary and Transparent Pigments – it was too good to ignore.
Buchanan suggests some different ways of looking at these characteristics, breaking the definitions down to Staining, Sedimentary, Luminous and then discussing the Quinacridones as a seperate set.
This article goes quite far into technique and layering the different forms of of pigment and is very much based around Daniel Smith’s range, but there are some useful insights to gain here.
Staining Pigments
Buchanan lists here Phthalos, Alizarin, “most of the Cadmiums”, Permanent Magenta, Hooker’s Green19, Indigo, Paynes Grey and the Quinacridones. She notes these flow in washes and do not lift – this interests me as while Cadmiums do stain, they do not like painting over in my experience.
Sedimentary Pigments
Buchanan’s list here is broadly coterminious with that of Wilson, though she only includes orange from the Cadmiums, and brings the cobalts under this group.
Luminous Pigments
Buchanan renames the Transparents as Luminous, noting that all watercolours are effectiely transparent, and this resonates with Wilsons advice that Opaques are used tranparently. It’s interesting to note almost all of these as she lists them (Viridian, Cobalt Blue, Aureolin) are granulating. She discusses using these as glazes, and does note their sedimentary nature.
Quinacridones
Buchanan makes special note of the Quinacridones as having luminosity with no negatives, and acting as stains when used in a first wash. I agree with these assesments, and they are indeed wonderful pigments.
The question is now, if we are looking into this detail, how far do we go?
In Summary
The answer to the question above is plainly “how far do you want to go?”
In my mind a basic understanding of organic/inorganic and natural/synthetic gives a very good start in understanding both how some basic pigment properties will be evident.
Often granulating and staining is seen almost as a binary, which to be is unhelpful. I think at the very least we need to look at granulating and non granulating, staining and non-staining. Transparency needs to be considered, but this is more complex as indeed is the exact nature of granulation.
Then we have issues such as activity in wet, and tendency to backwash, and in all these we need to also consider the exact way the paint is mader which can in some cases have as much as an effect.
Towards a set of properties for describing pigments
When we are discussing pigments, and their uses (in watercolour, this will differ to an extent) in other media, there’s several things we want to know. The origin is perhaps less important in use, but some people more than others may wish to avoid animal products, or those with specific environmental concerns.
Certainly we want to know about things like lightfastness, and how they perform in use.
Alongside the Staining, Granualtion, Opacity we would want to know the colour aspects – hue, saturation, and so on. Of course, even the same pigment could differ here due to slight variances and the exact way it is prepared. In general, I do not go so far as wishing to know the exact position in certain colour spaces in detail, preferring to rely on a visual swatch, but it can be helpful to know at least the vague colour type.
MacEvoy also looks at two further characteristics – that of activity in wet – how much the paint will diffuse out when dropped into a wash, and blossoming – the propensity to backwash if water meets the paint bead. These will of course be quite affected by the preparation (for example Schmincke watercolours are often quite active as I believe they use more oxgall than some, but particularly in some of the organic pigments there are trends.
So I propose, and will use in my descriptions the following:
Origin
- Natural Inorganic
- Synthetic Inorganic
- Natural Organic
- Synthetic Organic
This is pretty much agreed by all commentators subject to the discussion on laked pigments, above. I will treat a natural organic dyestuff, laked to a simple alumina or clay base to be a natural organic pigment. I will also treat natural pigments which have been artificially calcined20 as natural.
Type
This is where the matter becomes a little complex.
With synthetic organic pigments it’s relatively easy to break these down into chemical families and for the most part make reasonable assumptions about their properties therefrom. With Natural Organic Pigments it perhaps makes less sense to catagorise these in that way as many could be mixtures. For example, Tyrian Purple is predominantly 6,6′-dibromoindigo, which could be classified as an indole (a six-membered benzene ring fused to a five-membered nitrogen-containing pyrrole ring) yet the dye itself has other constituents, and as a pigment would traditionally be laked to stone powder. Indigo, is used as a pigment simply as the ground organic compound. Some natural pigments are very complex and contain various substances. Vine black, which is simply burned vegetable matter is mostly carbon.
Natural Inorganic (mineral) pigments may be based on one chemical, but may naturally contain impurities. Synthetic Inorganic Pigments may simply be lab based synthesised versions of the main chemical (such as Ultramarine, which is synthetic Lazurite) or they may be something enturely different, though some of the simpler ones may occur as minerals, even if not used as pigments historicallly in that form.
Natural inorganic pigments
By this I will include naturally gathered earths, and minerals, including were these have been artificially calcined. The key definer here would be that they are gathered naturally
MacEvoy21 includes:
- Red earths
- Yellow earths
- Green earths
- Lapis lazuli
- Azurite
- Malachite
The list is likely to need expansion, with more different mineral types being used again, and I will expand on this in a future post – for example I would most likely catagorise Lapis Lazuli as “Sillicate Minerals” and include Azurite and Malachite as a Copper Mineral – though if I was defining as I have with Lapis, this would be more accurately grouped as “Carbonate Minerals”.
Synthetic Inorganic
MacEvoy22 breaks these down into the following:
- Cadmium
- Chromium
- Cobalt
- Copper
- Iron
- Lead
- Magnesium
- Manganese
- Mercury
- Sulphur
- Titanium
- Zinc
This is obviously a useful (though perhaps incomplete, nowadays) list, as one may need to include cerium, bismuth, praseodynium and so on. Practically, there are considerations – For example Oxide of Chromium and Viridian are both (very similar) chromium compounds yet have very different characteristics in use, and Ultramarine is listed here as a Sulphur compound, yet it is not the sulphur that defines its artistic characteristics.
Natural Organic
As discussed above, this is quite complex. Many of these contain a key constituent that could be catagorised with a chemical family – but this may not be the best way of considering properties. It’s likey any definitions here would need to be wider and perhaps more narrative.
Synthetic Organic
In most cases one can get an idea of properties from the chemical families of these pigments. A list, again taken from MacEvoy23 could be:
- monoazo (arylide)
- disazo (diarylide)
- disazo condensation
- benzimidazolone
- beta naphthol
- naphthol AS
- metal complex
- isoindolinone
- phthalocyanine
- quinacridone
- perinone
- perylene
- anthraquinone
- diketo-pyrrolo pyrrole
- dioxazine
- triarylcarbonium
Colour
This is based on MacEvoy24 again, but is the most comprehensive and useful list I have considered:
- Green Yellow
- Yellow
- Orange Yellow
- Yellow Orange
- Orange
- Red Orange
- Orange Red
- Red
- Deep Red
- Violet Red
- Red Violet
- Violet
- Blue Violet
- Violet Blue
- Blue
- Green Blue
- Blue Green
- Green
- Yellow Green
- Earth Yellow
- Earth Orange
- Earth Red
- Brown
- White, Gray & Black
Warm/Cool
This is, as I have touched on and will again, a contentious matter. Where appropriate, I find this most useful in the context of a 4 colour (primaries plus green) wheel. This is simply due to usage, and the difficulty of mixing green from blue and yellow pigments.
- Cool Yellow
- Warm Yellow
- Warm Red
- Cool Red
- Warm Blue
- Cool Blue
- Cool Green
- Warm Green
Granulation and Sedimentation
- Granulating
- Slightly Granulating (by which I consider subtle granulations such as displayed by some quinacridones)
- Sedimentary (note that some of these may “granulate” in certain preparations, but essentially I am considering smaller particle sizes that are more opaque)
- Non Granulating (Flocculating)
- Non Granulating
Staining
- Staining
- Moderately Staining
- Non-Staining
Transparency
- Opaque
- Semi-Opaque
- Semi-Transparent
- Transparent
This is a complex one; for example, as I have noted Smalt may appear opaque in it’s individual particles, but cannot be seen as anything bu transparent in use. In general I mean Opaque to mean this can be overpainted light on dark, Semi Transparent I would class as heavy transparent stains (Phthalos, Dioxazine).
Lightfastness
- Excellent
- Good
- Fair
- Fugitive
And I will include a qualifier where needed (for example, tendency to brown).
Activity in Wet
- Active in Wet
- Moderately Active in Wet
- Inactive in Wet
Additional infomation may be needed, as this can be significantly effected by the vehicle.
Blooming
- Succeptable to Blooming
- Moderatelt Susceptable to Blooming
- Inert
Afterword
This is a work in progress, and I am developing this as I explore the subject. I will update this post if appropriate and indicate. Posts discussing the four main catagories will follow.
On Pigments
Getting to the bottom of how pigments (and indeed different preparations thereof) behave ultimately can become a bit of a rabbit hole. I will aim in this post to wander, perhaps cicuitously, through some of my thoughts and considerations when exploring and using different pigments in different ways.
Classifying pigments
On a very basic level, in my mind there are essentially four different types of classifying pigments. These are Natural Organic, Natural Inorganic, Synthetic Organic, and Synthetic Inorganic.
Natural Organic Pigments
are those made from plant or animal origin – though instantly the waters can be muddied to an extent as many of these are dyes and are laked (chemically bonded) to an inorganic precipitant (often aluminium hydroxide)1. Examples of these could be madder root, cochineal, indigo, Tyrian Purple, stil-de-grain (buckthorn berries). Other pigments may simply be ground plant or animal material – dragon’s blood resin, gamboge, charcoal, burned bones, peat, and (the favourite) asphatum from mummies…
Natural Inorganic Pigments
are metal or rocks which occur naturally, often metal oxides, oxide hydroxides, sulfides, sulfates, silicates and carbonates. This includes red, yellow and brown earths (iron oxides), green earths (clays containing large amounts of silica and the green minerals), slate, chalk, and coloured minerals such as lapis lazuli, cinnabar, malachite and so on. Virtually any coloured rock can become a pigment if it is ground finely enough.
Synthetic Inorganic Pigments
cover a wide range of compounds, from historical copper compounds such as bice, verditer, and verdigris, synthetic iron oxides made under controlled conditions, ranging through cobalts, cadmiums, prussian blue, french ultramarine (chemically identical to lapis) right through to complex modern pigments like the Siccopal pigments and YInMn Blue.
Synthetic Organic Pigments
are those based on organic compounds in chemcial terms (though a small subset may have other atoms like metals in their structure). These are often derived from petroleum products and tend to have wonderfully complex sounding names – arylide, diarylide, disazo condensation, perylene, isoindolinone, phthalocyanine, quinacridone, diketo-pyrrolo pyrrole, dioxazine and so on.
These catagories can go some way to help us to understand the artistic properties and uses of various pigments, but first, before we explore these further it is useful to think about pigments as catagorised by some of these properties, which can again be done in several different ways.
Transparent/Opaque/Staining/Granulating…
Perhaps the most basic catagorisations of pigments (or, to be more totally accurate paints as sometimes the way a particular preparation is made can change this) could be argued to two binaries of Transparent/Opaque and Staining/Granulation, and this is indeed often given as basic infomation by manufacturers2. For basic understanding of how a paint will behave, these are a good start, but instantly run into issues, for example some colours may be very opaque if you could apply them in sufficient mass-tone, but act to all extents as transparent in use (Smalt springs to mind) due to how they wash out and often granulate. Others may stain but still granulate – or at least are flocculating and sedimentary (some cadmiums). Others are classically seen as staining, and stain they do, but flocculate strongly due to hydrophobic properties in certain preparations (Phthalo Blue). To move further on from this there needs to be more nuance.
Kosavic – The Transparent Watercolour Wheel
These defintions of pigments as “Transparent”, “Opaque”, Staining, Granulating and so on have basic meanings which as we have discussed above, and in this sense do not take too much to understand, but they have a specific meaning in Jim Kosavic’s Book “The Transparent Watercolour Wheel”3 where he expands these to a set of specific qualities with general advice on how they react together in mixes and glazes.
These are as follows:
Transparent Non-Staining
As they suggest, these are colours with some level of transparency, which do not stain the paper and can be lifted to leave limited trace.
The key colours Kosovic lists here are: Rose madder Genuine (NR9)4, Permanent Rose (PR605), Cobalt Blue (PB28, also likely PB72, PB73 and PB74 which are other Cobalt Blue Pigments), Veridian (PG17), Hookers Green6, Aureolin (PY40).
In general they share similar handling characteristics – they will mix well with one another and you can generally mix more than two without getting to too muddy. Mixing with Opaque colours can clean up the opaques. Mixing with stains can be very effective, but can dye the transparent non staining colours and totally change the effect. Generally, they have a weak tinting strength and are light valued, making dark mixes difficult.
Semi-Transparent Non Staining
Reading on, you will note that there’s quite some cross over between the granulating pigments (discussed later) and the transparent non-staining and the transparency is to an extent created by the tendancy to granulate rather than cover thickly and smoothly. The Semi-Transparent Non-Staining colours are deeper, and a little more intense.
Kosovic Lists the following: New Gamboge7, Raw Sienna (PBr7), Quinacridone Gold (PO49)8, Quinacridone Burnt Orange (PO48), Burnt Sienna (PBr7), Vermillion9, Quinacridone Burnt Scarlett (PR206), Permanent Magenta10, Opera (Often PV19, with PR81/flouro), Permanent Mauve (Manganese Violet, PV15?), Prussian Blue/Antwerp Blue (PB27), Cyanine Blue11, Sap Green12, Green Gold (PY129).
Can be glazed without worrying abut mud, but care needed to avoid lifting. Mixing with Opaque colours can clean up the opaques. Mixing with stains can be very effective, but can dye the transparent non staining colours and totally change the effect. These tend to have darker values and higher tinting strengh than the transparent non-staining pigments.
Transparent Staining
These are colours that stain the fibres of the paper, that are brash, intense, saturated. Kosovic13 himself points out that the pigments used in these may well be very opaque in mass tone, but in use they are colours that would tend to be diluted and used in a wash. These are the Winsors14, and similar from other brands, essentially most modern organic pigments such as Arylides, Phthalocyanines, Napthols, Dioxazine Violet, Indanthrone Blue and so on.15 Kosovic includes Hookers Green light – perhaps meaning the Nitroso green, Carmine – uncertain if he means natural carmine – and Alizarin in this section. I would add some organo-metal compounds (Nickel and Copper Azomethines), Pyrrols, Pyrazolones, and Perylenes etc.
These can easily take over mixes, work well as glazes and are resistant to lifting. They will often flow into heavier colours – but this is to an extent affected by preparation.
Interestingly, Kosovic does not mention the Quinacridones here at all. We’ll discuss them later, in any case.
Semiopaque and Opaque
Kosovic lumps together a number of colours here – though what is important is that he notes that the usage of these is often transparent. He includes here: Cadmiums, Hansa Yellow (something which which I would not agree), some Quinacridones, Cobalts and Ceruleans, Manganese Blue, Bice, Ultramarine. I would add Nickel Titanate, Nickel Dioxine and some of the more modern compounds – YInMn Blue, Siccopal Pigments, Bismuth Vanadates and so on.
Kosovic notes that these will often mix ok with one other of their own type, and with transparent non-staining, but very quickly become muddy.
I will leave this section here, as I am going to expand somewhat on these shortly.
Whitened and Blackened Colours
Kosovic16 refers to these as “semiopaque and opaque colours which have some black or white in their composition”, which reads to me to sound like he is seeing many of these as mixes – however many of these are obviously single pigments. It is perhaps better to think of earths, blacks and whites. Kosovic lists Naples Yellow (most likely thinking of a blend), Ochres, Umbers, Sepia, Indigo, Terre Vert, Mars Violet, Blacks, Whites and Tints, but also Hookers Green Dark (mentioned elsewhere) andf Perylene Maroon (which I would class firmly a as a transparent stain.
In use, he suggests these are broadly the same as Semi-Opaques and Opaques, which for now I will leave as it is.
What is clear here is many of these are granulating or sedimentary, yet granulation is not restricted to these, some can stain, and not all follow a neat definition.
We need to go further.
Keene Wilson
Keene Wilson17 reherses and expands a little on the work of Kosovic, widening the discussion on the (semi)opaques.
He breaks down these into a few diffent catagorsiations, looking at “intense” opaques (in which he lists Cadmiums, Ultramarine, Mineral (Manganese) Violet, Cerulean, Manganese Blue, Hansa Yellow and Quinacridone Violet with the notes that two will mix, but must not be messed with, and echoes Kosvic that more than two will make mud, they mix nicely with transparent non-staining, but will be very dull when mixed with stains.,
He makes a special note on the Cadmiums that while these are some of the most intense colours (from opaques) they can be chalky and work in many ways better when pulled out, and do not like mixing with anything other than cadmiums.
He makes specific notes about some of the others, for example avoiding re-stating Cerulean, that Ultramarine does not mix well with various other opaques and so on. He also notes that Tom Hill (as so I) considers Hansa Yellow a transparent.
This breaks some of the outliers slightly out of Kosovic’s assessment.
Where this is important is that it begins to make the distinction between granulation and sedimentary colours – while similar they are distinct characteristics. Moving on one also needs to consider flocculation18. For me, at least, Cadmiums, Mars Violet (Caput Mortuum), Oxide of Chromium (to name a few) are better described as sedimentary than granulating. Qinacridones and some other organics are granulating, but the particle sizes are small enough this is very different than what we would consider true granulation. Cobalts, which Kosovic lists as transparent, are very granular. And Phthalocyanines flocculate very strongly, mimicking granulation due to their hydrophobic properties, and yet the preparations they are released in often have specific additives to prevent this.
Enter the Quinacridones!
I hope that Caroline Buchanan will forgive the minor plagairism of a subheading in her great article for Daniel Smith, Making Sense of Staining, Sedimentary and Transparent Pigments – it was too good to ignore.
Buchanan suggests some different ways of looking at these characteristics, breaking the definitions down to Staining, Sedimentary, Luminous and then discussing the Quinacridones as a seperate set.
This article goes quite far into technique and layering the different forms of of pigment and is very much based around Daniel Smith’s range, but there are some useful insights to gain here.
Staining Pigments
Buchanan lists here Phthalos, Alizarin, “most of the Cadmiums”, Permanent Magenta, Hooker’s Green19, Indigo, Paynes Grey and the Quinacridones. She notes these flow in washes and do not lift – this interests me as while Cadmiums do stain, they do not like painting over in my experience.
Sedimentary Pigments
Buchanan’s list here is broadly coterminious with that of Wilson, though she only includes orange from the Cadmiums, and brings the cobalts under this group.
Luminous Pigments
Buchanan renames the Transparents as Luminous, noting that all watercolours are effectiely transparent, and this resonates with Wilsons advice that Opaques are used tranparently. It’s interesting to note almost all of these as she lists them (Viridian, Cobalt Blue, Aureolin) are granulating. She discusses using these as glazes, and does note their sedimentary nature.
Quinacridones
Buchanan makes special note of the Quinacridones as having luminosity with no negatives, and acting as stains when used in a first wash. I agree with these assesments, and they are indeed wonderful pigments.
The question is now, if we are looking into this detail, how far do we go?
In Summary
The answer to the question above is plainly “how far do you want to go?”
In my mind a basic understanding of organic/inorganic and natural/synthetic gives a very good start in understanding both how some basic pigment properties will be evident.
Often granulating and staining is seen almost as a binary, which to be is unhelpful. I think at the very least we need to look at granulating and non granulating, staining and non-staining. Transparency needs to be considered, but this is more complex as indeed is the exact nature of granulation.
Then we have issues such as activity in wet, and tendency to backwash, and in all these we need to also consider the exact way the paint is mader which can in some cases have as much as an effect.
Towards a set of properties for describing pigments
When we are discussing pigments, and their uses (in watercolour, this will differ to an extent) in other media, there’s several things we want to know. The origin is perhaps less important in use, but some people more than others may wish to avoid animal products, or those with specific environmental concerns.
Certainly we want to know about things like lightfastness, and how they perform in use.
Alongside the Staining, Granualtion, Opacity we would want to know the colour aspects – hue, saturation, and so on. Of course, even the same pigment could differ here due to slight variances and the exact way it is prepared. In general, I do not go so far as wishing to know the exact position in certain colour spaces in detail, preferring to rely on a visual swatch, but it can be helpful to know at least the vague colour type.
MacEvoy also looks at two further characteristics – that of activity in wet – how much the paint will diffuse out when dropped into a wash, and blossoming – the propensity to backwash if water meets the paint bead. These will of course be quite affected by the preparation (for example Schmincke watercolours are often quite active as I believe they use more oxgall than some, but particularly in some of the organic pigments there are trends.
So I propose, and will use in my descriptions the following:
Origin
This is pretty much agreed by all commentators subject to the discussion on laked pigments, above. I will treat a natural organic dyestuff, laked to a simple alumina or clay base to be a natural organic pigment. I will also treat natural pigments which have been artificially calcined20 as natural.
Type
This is where the matter becomes a little complex.
With synthetic organic pigments it’s relatively easy to break these down into chemical families and for the most part make reasonable assumptions about their properties therefrom. With Natural Organic Pigments it perhaps makes less sense to catagorise these in that way as many could be mixtures. For example, Tyrian Purple is predominantly 6,6′-dibromoindigo, which could be classified as an indole (a six-membered benzene ring fused to a five-membered nitrogen-containing pyrrole ring) yet the dye itself has other constituents, and as a pigment would traditionally be laked to stone powder. Indigo, is used as a pigment simply as the ground organic compound. Some natural pigments are very complex and contain various substances. Vine black, which is simply burned vegetable matter is mostly carbon.
Natural Inorganic (mineral) pigments may be based on one chemical, but may naturally contain impurities. Synthetic Inorganic Pigments may simply be lab based synthesised versions of the main chemical (such as Ultramarine, which is synthetic Lazurite) or they may be something enturely different, though some of the simpler ones may occur as minerals, even if not used as pigments historicallly in that form.
Natural inorganic pigments
By this I will include naturally gathered earths, and minerals, including were these have been artificially calcined. The key definer here would be that they are gathered naturally
MacEvoy21 includes:
The list is likely to need expansion, with more different mineral types being used again, and I will expand on this in a future post – for example I would most likely catagorise Lapis Lazuli as “Sillicate Minerals” and include Azurite and Malachite as a Copper Mineral – though if I was defining as I have with Lapis, this would be more accurately grouped as “Carbonate Minerals”.
Synthetic Inorganic
MacEvoy22 breaks these down into the following:
This is obviously a useful (though perhaps incomplete, nowadays) list, as one may need to include cerium, bismuth, praseodynium and so on. Practically, there are considerations – For example Oxide of Chromium and Viridian are both (very similar) chromium compounds yet have very different characteristics in use, and Ultramarine is listed here as a Sulphur compound, yet it is not the sulphur that defines its artistic characteristics.
Natural Organic
As discussed above, this is quite complex. Many of these contain a key constituent that could be catagorised with a chemical family – but this may not be the best way of considering properties. It’s likey any definitions here would need to be wider and perhaps more narrative.
Synthetic Organic
In most cases one can get an idea of properties from the chemical families of these pigments. A list, again taken from MacEvoy23 could be:
Colour
This is based on MacEvoy24 again, but is the most comprehensive and useful list I have considered:
Warm/Cool
This is, as I have touched on and will again, a contentious matter. Where appropriate, I find this most useful in the context of a 4 colour (primaries plus green) wheel. This is simply due to usage, and the difficulty of mixing green from blue and yellow pigments.
Granulation and Sedimentation
Staining
Transparency
This is a complex one; for example, as I have noted Smalt may appear opaque in it’s individual particles, but cannot be seen as anything bu transparent in use. In general I mean Opaque to mean this can be overpainted light on dark, Semi Transparent I would class as heavy transparent stains (Phthalos, Dioxazine).
Lightfastness
And I will include a qualifier where needed (for example, tendency to brown).
Activity in Wet
Additional infomation may be needed, as this can be significantly effected by the vehicle.
Blooming
Afterword
This is a work in progress, and I am developing this as I explore the subject. I will update this post if appropriate and indicate. Posts discussing the four main catagories will follow.