TEACHING LETTER 1
September 21, 1993
Before starting to write about brushes, canvas, paper, mediums or colours (paints) I start with the hart which is the pigment.
By adding different liquids into the same pigment you obtain: watercolour-eggtempera-oilcolour-postercolour or gouache-polymercolour-alkydcolour-acryliccolour-soft pastel-oilpastel etc.
The quality of the pigment and the quantity of cheap fillers on one side and the kind of liquid indicates the type of colour mentioned here above. And that colour has more qualities as classic, artist, student and schoolquality.
The pigments can easy be divided in two sections:
1. organic pigments: chemical complexes
2. anorganic pigments: elements from earth
The chemical complexes are created during this century and carry names such as: pthaloblue, pthalogreen, azoyellow, naphtolred, quinacridone-rose etc. These colours you find be labeled under fantasienames as
Old Holland blue, Winsor blue, Grumbacher red, Scheveningen rose, Rembrandt blue, Hortensia blue (LB) etc.
The elements form earth carry names as cadmium, cobalt, ironoxide, chromium oxide, zinc, lead, manganese etc. Those colours carry names as cadmiumyellow, cadmiumred, cobaltblue, cobaltviolet, cobaltgreen, marscolours, persian-indian-english-venetian reds, chrome-oxidegreen and viridian, zincwhite, lead- or Cremnitzwhite, manganese blue -and violet. If you see a label with one of the above names followed by imitation or hue it is allways a cheaper replacement for the good pigment.
After we know now the two basic sections organic and anorganic, the quality of the pigment is next. Pigment-manufacturers can deliver the SAME shade $ 6,00 and also $ 70,00 a pound. Why??
The difference in price is caused by the next six points:
1. lightfastness (no colourchange in the sun by ultraviolet light)
2. colourpower or tintingstrength (a lot of white with a little bit of colour)
3. brightness (the colour stays clean even mixed with a lot of white)
4. intensity (the deepness of the colour close to the flower)
5. coveringpower (pure cadmium must cover at once even you paint thin)
6. filler which is already in the pigment (decreases the colourpower)
Cadmiumpigment can be obtained from the pigmentfactory pure or mixed with bariumsulfate which is a cheap filler like chalk. If this cadmium contains 50% filler the name is cadmium barium. This gives no guarantee for the label in your shop. I have tested tubes of cadmium barium which contained more pure cadmium as tubes with the name concentrated cadmium.
How is this possible? The manufacturer used 10% pure cadmium and added the filler by himselves and the truth is «he used concentrated cadmium». To solve this problem for the artist the most easy way is to compare the different brands cadmium bij mixing into the same white by volume. The deepest is the most powerful. Fillers are bringing all six above mentioned properties DOWN.
In TEACHING LETTER 2 I will explain the different liquids added into the same pigment to get different kind of paints.
Please keep this and the following letters in file,
so you build an extraordinary serie of professional art advices.
Prof. Th. de Beer
TEACHING LETTER 2
October 22, 1993
In this teaching letter I will explain the different liquids added into the same pigment to get different kind of paints.
First I show you nine different types op paint:
1. Pigment + arabicgum or dextrine gum + water + glycerine = WATER COLOUR
2. Pigment + arabicgum or dextrine gum + water + glycerine + filler = DESIGNER’S
3. Pigment + arabicgum or dextrine gum + water + glycerine + much filler = POSTER
4. Pigment + acrylic medium = ACRYLIC COLOUR
5. Pigment + polymer medium = POLYMER COLOUR
6. Pigment + alkyd medium = ALKYD COLOUR
7. Pigment + water = FRESCO
8. Pigment + egg = EGGTEMPERA
9. Pigment + oil = OIL COLOUR
Referring to the above 9 different paints it is good to know for instance «WHAT IS THE DIFFERENCE BETWEEN WATER COLOUR AND DESIGNER’S GOUACHE» and more other questions. So I will put 1-2-3 and 4-5-6 together to compare.
1. WATER COLOUR – 2. DESIGNER’S GOUACHE – 3. POSTER COLOUR
They contain all three about the same raw materials.
TRANSPARENT WATER COLOUR COVERING DESIGNER’S GOUACHE
pigment LESS pigment
NO filler filler
boiled water boiled water
arabic- or dextrine gum LESS arabic- or dextrine gum
glycerine MORE glycerine
Water colour contains more gum and can be painted very thinly by adding water. If you paint thinly with designer’s gouache which contains less gum the paint peals off. Gouache is destinated to paint thick and must be more flexible for that reason it contains more glycerine.
A small quantity of filler is added into the gouache paint which gives a higher covering power. If you add more filler you get a cheaper poster or school colour which has not the covering power of designer’s gouache. Also by these paints (poster and school colour) cheaper not lightfast pigments are used.
4. ACRYLIC COLOUR – 5. POLYMER COLOUR – 6. ALKYD COLOUR
They contain all three liquid plastics which are quick drying and flexible. You can not paint long time wet in wet. The most lightfast binder is first acrylic than polymer and next alkyd. The flexibility and the drying time are in the same order.
They must be varnished all three because by hot weather the paint becomes sticky and absorbs easily dust. Put or roll never two paintings with the surfaces to each other; they will stick together. Alkyds will be harder than acrylic and polymer and less sticky because the liquid plastic (alkyd) is mixed into the oil.
By freezing temperatures your acrylic and polymer paintings will become brittle and show cracking effects and the pots and tubes in your shop will be destroyed. The above 3 paints must contain substantial quantities of gelbutters and or fillers for conservationproblems in the shops. If you mix pigment only with one of those three binders your paste will turn into chewing gum and later into rubber gum even if the paste is packed by you into a tube or in closed glass jars.
Use allways pigments which are alkali resisted on walls. Prussian blue for instance is a wrong pigment for this purpose. To make fresco colour sometimes 5 till 10% glue is added into the boiled water to mix with the pigment to be better adhesive.
The eggtempera is much replaced in ± 1600 in Holland by the oils, because it is so brittle. For underpainting it is used mostly today in order to cover it later with oil colour. Also it is used on white primed wood (ICONES). The egg was sieved (TODAY NYLON SOCK) and a drop of vinegar for conservation purposes was added. To make eggtempera less brittle take 1/3 sieved egg 1/3 dammarvarnish and 1/3 cold pressed linseed oil as basis together with your drop of vinegar. By adding only water into the above medium you make picture varnish. By adding more water the varnish becomes more mat.
9. OIL COLOUR
The «classic» oil colour is less brittle than eggtempera but more brittle than acrylic/polymer/alkyd colour. The oil colour should be painted fat over lean otherwise it will wrinkle, but you can paint long time wet in wet caused by the slow drying time.
The different oils are:
– SAFFLOWER OIL : very slow drying time, brittle, needs driers but is not yellowing;
– POPPY OIL: medium drying time, medium brittle but yellows a little bit;
– HOT PRESSED LINSEED OIL: quicker drying time, less brittle but yellows in the dark (night) and becomes clearer in the day.
If the linseed oil is cold pressed the properties will be more improved than hot pressed linseed oil because the linolenic acids are saved in the oil. This also gives a more perfect brushstroke.
In TEACHING LETTER 3 I will explain the differences of paint in:
1. SCHOOL QUALITY
2. STUDENT QUALITY
3. ARTIST FINE QUALITY
4. ARTIST EXTRA FINE QUALITY
5. CLASSIC QUALITY
Prof. Th. de Beer -2-