I have recently read Golden’s technical specialist, Trevor Ambrose’s article in Just Paint , Sept 24, 2023, on the results of lightfast tests of 34 selected WB oil colors when mixed with several whites. This is a significant revelation as it suggests that the usual ASTM lightfastness ratings seen on color tubes and on The Art of Color and other websites are not entirely reliable as a measure of a pigment’s lightfastness when in use with white.
If you look at the lightfast results in the article, it is obvious that many, but certainly not a majority, were particularly less lightfast in lead white than in titanium and not what would be expected for the pigment alone. The most notable ones for me were cobalt blue, cad yellow medium, and ultramarine blue all moving fom ASTM I to II. (Note: I am not picking on WB or casting any aspersions on their oil colors whatsoever and use their products consistently, but WB, Gamblin and Natural Pigments, to their credit, were the only paint manufacturers to participate in this investigation so I suspect that they used their own colors for the tests. The tests may reliably shed light on most if not all tested pigments regardless of oil paint company.)
I have been a user of WB lead white both alone in bottom paint layers and mixed 50-50 with WB or Gamblin titanium in upper layers to achieve some of the benefits of both whites in paint layers. I am now considering using titanium alone throughout and using up the lead white for studies and landscape sketches alone but not for larger finished paintings. (I use Graham’s walnut alkyd and Gamblins alkyd lite for my medium, with a little stand oil for the viscous paint at the bottom of the tube before adding alkyd. I paint finshed paintings on alumalite and dibond with pH neutral PVA sized 140 cotton watercolor paper for studies, sketches and tests.)
1. Are the benefits (stronger, harder and more flexible paint film than titanuim) of lead white worthwhile, considering the loss of color lightfastness, from ASTM I to II, in 3 of 8 colors in my palette? If the test results seen in Trevor Ambrose’s article are correct, the lightfastness of cad yellow medium and cobalt blue remain at ASTM I with the use of titanium white. Ultramarine blue still drops to ASTM II.
2. Would the continued use of alkyd as my medium be more than sufficient for film strength without the use of lead white?
I have followed ASTM ratings for many pigments both on line and on color tubes and have memorized many of them. (No ASTM II’s please.) But if the results of these tests on 34 pigments are correct, I may have to re-evaluate my painting materials a bit.
Thanks for your thoughts,
Richard
These are questions subject to a degree of personal relativity of what’s considered most worth while. As I type this I recall some released study on paint films done by I believe the Smithsonian. Titanium white bound solely in alkyd performed quite well and better than titanium in linseed. Linseed Lead white performed very well in the general goldielock zone, but alkyd lead white (like zinc white) aged to a too hard slighly brittle state.
Now perhaps alkyd mediums added to titanium oil tints on a panel are all that’s needed, but how much alkyd? Would alkyd titanium white be better? Regarding lead white, is ASTM II really that bad considering that ASTM II pigments show their most noticeable fading in tints where they drop well below ASTM II to III or even IV?
Unfortunately when it comes to being exact I’m afraid here that I simply don’t know.
Fellow painter, Marc.
Thank you, Marc.
1. When you say “alkyd lead white” do you mean lead carbonate mulled into an alkyd paint or lead carbonate paint with some alkyd used as a medium by the painter? The former brings much more alkyd to the paint layer than the latter .
2. “Titanium white bound soley in alkyd”… an alkyd paint or an oil paint with some alkyd used as a medium by the painter?
I’ve never used alkyd paints, if that is what you are referring to, but have been using some alkyd only as a medium in my oil paints as the least yellowing, hardest and most flexible medium (recommended by one of the paint experts on AMIEN a decade of more ago.)
One of my traits, perhaps a fault, is too segue needlessly. The alkyd lead white was a basic lead carbonate mulled in alkyd and made by Winsor & Newton not lead white oil paint with alkyd medium added. Winsor and Newton no longer make it so why did I bring it up?
Again a pigment mulled in alkyd. This was also probably made by Winsor & Newton. Supposedly it’s safe to mix the two types of paint but how much testing have they actually done on it? Probably safer to just keep mixing alkyd medium into oil paint.
In my own practice I’ve found that stand oil is the most flexible, but then I’ve only tested paint and oil films that are a few years old.
Marc.
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