F.W. Andrew's Experiments

The experiments of the late F. W. Andrew, formerly of the Victoria and Albert Museum, have been carried on since 1876, but have been confined to water-colours, both moist and cake. His chief results will be found recorded along with my own, in Part III., in the paragraphs devoted to the consideration of the several pigments. His water-colour washes, generally spread on Whatman paper, or Whatman board, were exposed for periods varying from twenty-eight to eighty-two months, in a south window, to all the sunshine available; half of each wash was doubled back, and so far excluded from light. In some cases a third part of the coloured slip was exposed to the air and light without the protection of glass. The chief paints which were unaffected, at all events, so far as some specimens were concerned, by the exposure, are included in the following list: Yellow ochre, raw sienna, deep cadmium, Mars red, light red, Indian red, oxide of chromium, Leitch's blue, cobalt, artificial ultramarine, Prussian blue, raw umber, burnt umber. Naples yellow (true) became blackish in darkness, but was unaltered in light, while orange chrome showed dark patches. Further details must be given as to the pigments which were affected. In the tabular statements appended a selection from the results afforded by eleven sets of experiments is recorded, the letters C and M prefixed to the entries respectively denoting the employment of cake or moist colours. The numerical values representing the residual hues are rough approximations only, but in some instances they were determined by means of comparisons with standard coloured liquids, contained in glass cylinders graduated into ten equal parts. Hellige's colorimeter or the tintometer of Mr. J. W. Lovibond, of Salisbury, may be employed with advantage in these estimations.

Changes In Water-Colours

The pigments containing lead, such as the ordinary chromes, and those having a copper basis, like emerald green, had altered capriciously, losing part of their original colour, and becoming tarnished or embrowned in patches. Brown pink faded like the yellow lakes, but acquired a bluish-grey residual hue.