Lead white

About the chemical structure:

Chemical name:	Basic lead(II)-carbonate
Formula:	2 PbCO3· Pb(OH)2
Crystal system:	Trigonal (at Mineralogy Database)
Refractive index:	Uniaxial (-), e = 1.94, w = 2.09

How can you identify Lead white?

Imaging:

UVF: pale white

IRFC: white

OM: Particles exhibit high birefringence. Polarisation shows bright white crystals, a few may appear to be orange orred.

Microscopic appearance at x500 mag

Analytics:

It's identified by means of FTIR and Raman.

Raman spectra: University College London;

FTIR spectra: IRUG

Usage and handling:

Permanence:

Toxicity:

lightfast: excellent Degradation processes: its surface is blackened on contact with sulphides in the air causing the chemical reaction of lead carbonate to black lead sulphide. The lead hydroxide part of lead white molecule is able topartially 'saponify' linseed oil to form with it a lead soap called lead linoleate. This fact has been used to explain why lead white in oil forms has such a hard and porous paint film. It is also a given reason for the transparency of aged lead white paint films.

toxic. Cerussite is toxic and care should be used in handling the dry powder pigment so as not to inhale its dust, as well as the pigment dispersed in medium. MSDS: Kremer

Literature:

Kühn, H., Bleiweiss und seine Verwendung in der Malerei I. und II., Farbe und Lack, 73, 1967, p. 99-105 and 209-213

R. J. H. Clark and P. J. Gibbs, Raman Microscopy of a 13th Century Illuminated Text, Analytical Chemistry (vol 70, p 99A)

Artists’ Pigments. A Handbook of Their History and Characteristics, Vol. 2: A. Roy (Ed.) Oxford University Press 1993, p. 67-81