Gouache, from the Italian guazzo, is a method of painting with opaque colors ground in water and thickened with gum and honey. The Head of Conservation at The Bergen Museum of Art, MSc. Yngve Magnusson, was so kind to send me over a Winsor and Newton Color Chart of Designer’s Gouache to be tested by Technical Photography. I thought it useful to share this information that complements the previous post on historical pigments. Fortunately, Winsor & Newton provide detailed notes on the pigments in this color chart, here.
Winsor & Newton Designers’ Gouache Color Chart. Normal Photography.The following Technical Photography documentation was done as described in the just mentioned post. The only difference is that the reference swatches zinc white and cadmium red are put aside on the far left.
Some highlights from the Ultraviolet Fluorescence imaging: overall this pigments are pretty dull but some pigments such as Bengal rose show a mild red fluorescence (indeed it contains a fluorescent dye).
Winsor & Newton Designers’ Gouache Color Chart. Ultraviolet Fluorescence PhotographyMore useful is the UV Reflected Imaging. Indeed, Cerulean blue and synthetic ultramarine mildly reflect UV. But cobalt blue is a strong UV reflector. This turns useful for its identification.
Winsor & Newton Designers’ Gouache Color Chart. Ultraviolet Reflected Photography.Looking at the Infrared Photo I was caught by the IR absorbency of Indigo which in my collection is actually IR transparent. Indeed, The indigo in the color chart is not a real indigo as stated here.
Winsor & Newton Designers’ Gouache Color Chart. Infrared Photography.The Indigo swatch looks suspicious also in the infrared false color where it should be red instead of pitch black.
Winsor & Newton Designers’ Gouache Color Chart. Infrared False Color PhotographyThe cadmium pigments (red, orange, yellow) in this color chart look intensely IR fluorescent as expected.
Winsor & Newton Designers’ Gouache Color Chart. Infrared Fluorescence Photography
I am looking at a Winslow Homer watercolor from 1873 that has a mustard yellow florescence of the white gouache media. I am uncertain whether I am looking at the florescence of the binder or the pigment. There also seems to be some yellowing of the paper to either side of the white highlights. Not sure if this is an indicator of incompatibilities of media or of the pH of the media.
Any thoughts?
Hi Leslie, I don’t know if I’m getting the all picture right and I’m addressing your question correctly. A white pigment which shows yellow UV fluorescence is zinc white. Did you mean actually florescence?
Hi Antonino,
I know what the florescence of zinc white looks like. This is quite different. Maybe not a true florescence. It looks more like a dull mustard yellow. Could be a binder that has dulled down the florescence of the pigment.
Have you seen this? It is a very opaque white. Pretty sure a gouache.