Identification of CaCuSi<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"><mml:msub><mml:mrow /><mml:mn>4</mml:mn></mml:msub></mml:math>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"><mml:msub><mml:mrow /><mml:mn>10</mml:mn></mml:msub></mml:math> (Egyptian blue) in the “Birch. Spring” painting by Robert Falk (1907) using photoluminescence

We have detected Egyptian blue pigment in the paint layer of "Birch. Spring" painting by Robert Falk (1907); we also found this paints sketch drawn on canvas back side. This is probably first discovery a 20th century work art. analyzed modern commercial (Kremer) and it to be suitable as standard for photoluminescence spectral analysis. The characteristic band CaCuSi$_4$O$_{10}$ reaches maximum at wavelength about 910 nm. luminescence efficiently excited incoherent green or light. study demonstrates that micro analysis using excitation light can used identification luminescent pigments layers artworks.