Technical notes - Fleming Art Group

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These are notes about technical issues in art in the hope that they
will be useful to someone - Geoff Wright
My previous technical notes are listed below

TN001 - cropping photographs on the computer

7 July 2018 TN005 - Darks
I have just produced a Watching The Paint Dry piece on shadows and underpainting and I found I was having to consider the correct paint to use for the darkening effect so I decided to write this separate Technical Note on dark paints and paint mixtures. I mentioned the use of black paints in WTPD004 - Palettes and colour mixing and I also went back to the problem in WTPD005 - Wishy washy watercolours but I did not consider the whole field of dark paints. One of the requirements for underpainting is that the paint should not be too easy to lift so I am looking for paints which stain.

There are a number of black paints available to us

Pbk6 lamp black soot from burnt petroleum or wax
PBk7 furnace black from burnt coal wastes or natural gas
PBk8 charcoal black from burnt willow stems
PBk9 ivory black from burnt animal bones
PBk10 powdered graphite
PBk11 Mars black ferrosoferric (iron) oxide
PBk31 Perylene black (or green) also known as shadow green

All these are staining pigments and all but the last two are carbon in different forms. We are told not use black in our paintings but the real advice should be not to use the various carbon blacks because the carbon dries to highly reflective particles which reduces its darkness and makes it appear dull. A very similar problem is graphite shine which is the subject of a recent article by Phil Davies of Art Tutor on graphite shine. Here is the link 

Mars black, which is a ferric oxide, is better at producing a more intense black than carbon.

However, the advice is to make up a dark paint using a combination of pigments such as phthalocyanine blue, quinacridone gold and permanent alizarin crimson as suggested by Ali Lindley or the 'synthetic black' advocated by Bruce MacEvoy, he uses indanthrene blue, burnt umber and phthalocyanine green in an approximate ratio 8:6:1.

The problem with paint mixing is getting consistency, Bruce may be able to accurately judge an 8:6:1 ratio using a paint brush but I can’t so I prefer two colour mixes. Any two pigments which have a mixing line passing through the centre of the artist’s colour wheel will make a good gray.

However, to get a good black the two pigments need to be dark valued which can be checked using Bruce MacEvoy's artist’s value wheel.
A suitable pair are perylene maroon and phthalocyanine green BS, roughly in the proportions 5:1 and another pair is quinacridone orange and iron blue in roughly 4:1 proportions.

However as described in WPTD006 – Shadows and underpainting I have settled on perylene green (PB31) mixed with dioxazine violet (PV23) both of which are staining and the mixture creates a darker and more stable black than most carbon based paints. Here is the mixture at various dilutions.
There are other dark valued paints which may be used instead of black or a mixed black.

Neutral tint was developed by 18th century English watercolourists as a mixture of light red (red iron oxide) and indigo (or iron blue) with a touch of yellow, such as gamboge or yellow ochre. It was preferred to sepia ink as a neutralizing mixer or a foundation tint because it did not dull either warm or cool paints. Most artists today use a neutral tint in preference to a pure carbon black, however most available neutral tints are mixtures of lamp black with a dark blue and red to give the colour a slight but noticeable violet bias. The mixture is typically used to dull and darken paints, and to provide a shadow colour, without changing the apparent hue of mixtures; it also makes an effective stormy sky colour, modulated by added blue or violet.

Payne’s gray was developed by William Payne as a mixture of iron blue, yellow ochre and a crimson lake, used as a dark violet shadow colour. Modern versions of Payne’s gray are made of phthalo blue, quinacridone red and lamp black, all are staining.

In your painting, you don’t always have to use straight black, neutral tint or Payne’s gray. Dark blues, greens, and browns are also an option. You can still get a rich, dark colour this way and it prevents that dull and muddy look of using too much straight black. Some of the paints that can be used are described below.

Indigo originally an anil dye used for blue jeans which as we all know fades quite rapidly. Now made with lamp black, red oxide and phthalo blue or phthalo blue, lamp black and quinacridone violet or indanthrene blue and lamp black, these are all staining.

Sepia originally a pigment produced from the ink of cuttlefish it is now made from iron manganese oxide and furnace black or red oxide and lamp black, these are all staining.

Indanthrene blue which is a very dark blue with violet tinge, heavily staining.

Prussian blue or iron blue a very useful and dark blue when used a low dilutions, staining.

Dioxazine violet which is a very dark violet, heavily staining.
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