Detecting artistic fakes: pigments and dyes, partners in expertise
At the beginning of the 19th century, chemistry underwent its great revolution
Industry was booming and making its way into everyday life. And ready-to-use colours made painters happy. At the end of the century, after years of research, new syntheses and experimentation, new synthetic pigments appeared, and the list grew rapidly until the middle of the 20th century. Some pigments are still in use today, while others have lost out to competing pigments with deeper, longer-lasting or less toxic hues.
This marvellous story can be read by chemists in patents from all over the world, especially Germany, the United States and France.
This story is very useful to us when it comes to studying contentious works.
Today we'll take the example of Hansa Yellow pigments. Behind this poetic term lies a particular chemical family with a chemical function that varies the tonality, UV resistance and oxidation resistance of the dye.... and this family has several generations that, like a birth certificate, have a dated and geolocated patent for each generation.
We will take as an example the study of a work in gouache on paper attributed to a French artist from the early 20th century. The work is first observed under high magnification and different lighting conditions in order to locate any traces of retouching or restoration.
A micro-sample of the yellow background on which the signature with the date "1950" is affixed is taken and characterised: it is a Hansa yellow developed in.....1957!
Is this an authentic original design that has been repainted? A completely anachronistic design?
In both cases, the signature cannot be original.