My recent piece about the latest Winsor & Newton limited edition set raised a number of interesting questions. One of these was what was the point of buying them and wanting more, when you would be unable to buy replacements? Primarily due to the researches and knowledge of a Facebook friend Zvonimir von Tosic we now possibly have some answers. I know that many artists are not that interested in pigments as such but it is a subject that fascinates me, even though I don't claim great technical expertise in either knowledge or approach. Without Zvonimirs input this piece would not have arisen so I am greatly indebted to him for discovering things are not as simple as they sometime appear.
Previously I have always consulted Handprint - and still do - even though Bruce McEvoy ceased to update it several years ago.Much is still relevant but like all things nothing stands still. The pigment database- artiscreation.com/ColorCharts.html - is also a good source of information but quite technical.
Here is what Zvonimir has to say and I quote him in full:
"All right, I think I have an answer Peter. I have explored a little, so here is a brief summary. When producing certain types of pigment, say PV15 (this is one of the pigments used in a paint they call `Smalt' in the latest W & N limited edition -PGW)., pigment manufacturers can obtain different `shades' of the colour, perhaps hundreds, depending on manufacturing process (errors, trials, beginning of run, end of run, stability of process etc).
However when analized spectographically, the wavelengths of all those batches are still within the acceptable range to be named PV15. But, our eyes being very sensitive to nuances, can tell the difference. In your tests of paints made `from seemingly same' pigments, but coming from different paint manufacturers like W & N, DS or Schminke, they may appear to differ. Therefore numbers`after' the number 15, and all manufacturers try to buy batches closer to their chosen shade.
What if all of them want to buy same, and at the same time, and there isn't enough ?
See chart (above). It shows variations on PV15 and PV14, which one pigment manufacturer is able to obtain( or has saved them in stock) in quantities ready to be utilised. They may keep batches piling up, or offer them to some paint manufacturers at a discount, who can make an interesting product out of them.
W & N reads industry newsletter, makes a phone call, takes a few tonnes of (PV)15583 for example, which looks bluer than what they used to buy for PV15, (in this case it may look like old Smalt). W & N purchases it, makes a limited run tube paint - perhaps because the manufacturer of that pigment does not or can not produce that specific variation in large quantities, and W & N knows what their users normally buy, with what types of colour shades users are happy with and can appreciate.
Colour recognition is a cultural phenomenon, and they play by the rules"
This has certainly widened my understanding of this subject. As said many may not be interested but to me it goes a long way to explaining why Permanent Rose from W & N (PV19) is such a favourite. And this applies to certain colours from other makers. I was aware that there are variations in pigments and have done posts where this has been highlighted, for example PV19 where we have red, rose and violet shades.
One thing puzzles me slightly. Basically pigments are in two categories, natural and synthetic. With natural pigments like the earth colours there is considerable variation in shades, but I can understand this as they are mined and colours vary. Although it has been said these natural supplies are running out, and synthetics (PR101) are replacing them, there are still many available sources, perhaps not in such large quantities. If you visit Provence you'll see this with shops selling nothing else and all sorts of colours visible in the rocks. In the Forest of Dean about thirty miles from where I live, between Bristol and Bath, are Clearwater Caves, a tourist attraction. Several earth colour shades are still mined there and sold in the shop, and on the internet I believe.
With synthetics I would have thought they would be more consistent, being produced by a chemical process. I know the final result is determined to some extent by how the paint maker process the pigment and what additives they use.
Here are five swatches, three of Ultramarine, two of PV14. The Graham Ultramarine Blue looks much darker than the other two but this may be my fault. Holbein and W & N look much closer. The above swatch is actually W & N French Ultramarine, and they also offer an Ultramarine `Green Shade'. With PV14 I've had problems with the Rowney version changing colour, a sludgy brown, and going hard in the tube. Another violet shade PV16, from Graham gave all sorts of problems and even the so-called final one - the third I received, using pigment from a different source according to Graham, has now also bitten the dust and has set like concrete!
As a final word Zvonimir has established from Graham that nowadays the same pigments are used in oils, acrylics and watercolours and the particle sizes are the same. This was apparently not so in the past.