THE DEVELOPMENT AND INITIAL APPLICATION OF A GAS CHROMATOGRAPHIC METHOD FOR THE CHARACTERIZATION OF GUM MEDIA
SARAH L. VALLANCE, B.W. SINGER, S. M. HITCHEN, & J. H. TOWNSEND
These initial investigations have provided a simple derivatization method and GC technique for the characterization of natural gum-based artists' media, facilitating the identification of small and complex samples taken from temperas by William Blake.
It appears that in the paintings studied, Blake used some unusual mixtures of plant gums and sugar. These findings have raised questions regarding the gums available to artists of this period and have prompted further investigations.
Hexamethyldisilazane proved an adequate silylating agent for the neutral sugars, though further work is needed to investigate the points raised in the discussion regarding the problem of the repeatability and reproducibility of the acid hydrolysis and silylation of uronic acids. One possibility would be to replace the acid hydrolysis stage of the sample preparation procedure with the alternative technique of methanolysis as used by Ha and Thomas (1988).
The authors wish to thank Tate Publications for their permission to reproduce illustrations of Blake's works; Stephen Hackney, Dr. Tom Learner, and Roy Perry for reviewing the manuscript; and Ed Ludkin and Angela Pocklington for their technical assistance.