Materials and Techniques
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The materials used in the studio experiments were all available in Vermeer's time. Great care was taken to prepare the surface of the canvas in a way he would have recognised; and pigments were ground by hand into cold pressed linseed oil. This experiment took a year to complete not only because grounds had to be dry and prepared ready to receive a print, but also because it took time to refine a successful technique.
Reference was made to the scientific examination of Vermeer's painting and to what is known of painting techniques of the 17th century and before.
Traditional stages in painting
Painters of Vermeer's time worked in a prescribed order, laid down in 'books of secrets' and in methods passed down in painters' workshops. This experiment followed the traditional order of painting.
Monochrome images were traced and transferred from a projection to a canvas using a rudimentary form of printing. Once on the canvas, they acted as the inventing layer.
Because the image from the lens is corrected as it is transferred, the artist could do the majority of his work conventionally; working up and finishing in the light of the studio; while facing the subject.
The use of the camera obscura was not well documented in Vermeer's time, and it was common for artists to keep their working methods to themselves.
Oiled Paper
The vital element in this experiment was the use of oiled paper to transfer wet paint tracings to a dry, primed canvas. Oiled paper is easily prepared, and is transparent, allowing registration marks to be lined up with images on the painting surface. This means that multiple tracings can be made from the camera projection, and that transfers can be made to the canvas at different stages of the painting.
Oiled paper has long provided a material on which to trace. Cennino Cennini gives a recipe for its preparation in his book published in the late 1390s. In Vermeer's time oiled paper was used on the screens of box cameras obscura, and also had domestic uses, in making shades on windows, and covering food.
Oiled paper degrades over time and eventually becomes brittle and useless. Any tracings would have a limited use and lifetime. Should Vermeer have used oiled paper for drawings or tracings, this would be one of the reasons that none has survived.
 Paper marked with the date 1684, half oiled in the studio with cold pressed linseed oil. This is so transparent that a copy of ‘The Times’ can be clearly read beneath it.
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 The same paper with a detail tracing at actual size of ‘A Woman holding a Balance’, seen with paint side down.
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Preparation of the canvas
Fine Belgium linen of weight 265 g/m2, and with a thread count of 17threads warp and 15.4 threads weft was used for all the canvases in this experiment. The thread counts in Vermeer's canvases were often equal for warp and weft, often 14 or 15 threads per cm2.
One trampoline canvas of the kind used in Vermeer's time was constructed to receive a detail print of 'The Music Lesson'. Other canvases were stretched onto wooden stretchers with wedges. Although these were not available in Vermeer's time, they were easier to prepare and would not affect the quality of the surface of the ground.
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Chalk and rabbit skin glue for the first layers of the canvas.
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Stretching the trampoline canvas.
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There is debate as to whether Vermeer prepared all his own canvases, or if he bought them ready made up and ready primed.
Canvases were often prepared laced to frames, and then cropped and transferred to strainers. It is difficult to know what Vermeer did because nearly all of his paintings have been re-lined.
The canvases in the studio were sized with warm rabbit skin glue and when dry, painted with a very thin flexible coat of gesso. This was rubbed down before the ground was knifed on.
Pigment and Oil
All of the paint used in this experiment was hand ground using authentic pigment and cold pressed linseed oil. The paints for the grounds were prepared with different ratios of lead white to chalk and to earths, with reference to the grounds on Vermeer's paintings. One canvas was given a double ground of grey over red. Vermeer's The Love Letter is known to have a double ground like this, as have many canvases of Rembrandt.
All the grounds were knifed onto the canvas, and when dry rubbed down slightly with a pumice stone to present a dusty surface ready to receive a print.
Great care was taking in this stage of the process because some of the pigments used are poisonous.
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Equipment for grinding paint, lead white pigment and cold pressed linseed oil.
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Earth pigments with lead white pigment and chalk, before grinding into oil.
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Pigments ground into cold pressed linseed oil, ready to be knifed on the canvas.
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Applying the ground onto the gessoed canvas.
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Paint for tracing
In order to be able to see the tracing as it was being applied on the oiled paper under the projection, the tone of the tracing paint needed to be dark. This paint also needed to be slow drying and just thick enough not to run.
Many experiments were attempted using paint made with lamp black, but because the particle size of this pigment is so small, this paint was too strong and oily for printing, and resulted in smudged transfers. Bone black pigment worked very much better because its larger particle size made a weaker paint.
Once the image had been printed onto the canvas it was found that large areas could be easily strengthened with lamp black.
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Bone Black pigment, ground into oil. This would be thinned with a little more oil for tracing.
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Print from a detail of 'The Music Lesson' at actual size onto the trampoline canvas with a chalk and white ground.
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Brushes
The brushes used to make tracings on the oiled paper were hand-bound fresco brushes. These held just enough paint to make a good mark on the paper but could still convey some detail.
Hand bound fresco brushes, used for tracing onto oiled paper.
The use of relatively broad brushes corresponds with recent analyses of Vermeer's underpainting, as does the use of bone and lamp black.
Colour
It is known that painters of Vermeer's time worked with small palettes and used colour carefully, because pigment was expensive, and because paints were difficult to keep in a workable state. In the 17th Century artists had to prepare much of the materials for painting themselves, and some pigments would have been of uncertain quality or refinement.
Earth colours would have been laid down under paints made with more expensive pigments. The pigments used in this experiment were all those found in the scientific analysis of Vermeer's painting. Surprisingly little colour was needed to be put on top of the printed 'underpaintings' for these to have an impact.
Suppliers of materials
Zecchi, Via dello Studio, 19/R- 50122 Firenze: Arzica (weld), smalt, verdigris, bone white, malachite, fresco brushes. http://www.zecchi.it/
Ditta G.Poggi, Via del Gesu, 74/75-00186, Roma: Carmine red (rosso laccato francia) http://www.poggi1825.it/
Arcobaleno,S.A.S. Di Nube Massimo & C. - Pigmenti E Belle Arti San Marco, 3457, 30124, Venezia: Red earth, yellow ochre, natural umber, fresco brushes.
Cornelissen, 105 Great Russell Street, London WC1B 3RY: Lead white, bone black, lamp black, lapis lazuli, madder, massicot (lead yellow), natural indigo, cold pressed linseed oil, linen canvas, glass muller. http://www.cornelissen.com/
Green and Stone, 259 Kings Road, Chelsea, London SW3 5EL: Rabbit skin glue. http://www.greenandstone.com/
Great Art, Normandy House,1 Nether Street, Alton, Hampshire, 1EA. www.greatart.co.uk: Stretchers.
http://www.greatart.co.uk/
Tiranti, 27 Warren Street, London W1T 5NB: Whiting for gesso. http://www.tiranti.co.uk/
Casa Hernanz, cl Toledo,18.28005 Madrid: Linen string for trampoline canvas. http://www.madrid.com/madrid_tourism/shop/casa_hernanz
casahernanz@hotmail.com
Shepherds Falkiners, London: Paper (RM 1790’s laid 65 gsm 680x510 natural). http://www.falkiners.com/
Anthony Davenport Prints, Abingdon, Oxfordshire: Antique paper.