We have elsewhere recommended, without knowing that it was an old practice, the use of white chalk and such substances with the colours, and are therefore pleased to find the following notice,--"White chalk, marble dust, gesso, the bone of cuttle-fish, alumen, and travertine, were occasionally used in white pigments. They were frequently mixed with transparent vegetable colours, to give them body:" it might be added to give them, by a semi-transparency, and that even to colours in their own nature opaque, a luminous quality.
Does "grana in grano," the Spanish term for the scarlet pigment, show the origin of the expression, "a rogue in grain." "Pierce Plowman, whose _Vision_ is supposed to have been written in 1350, in describing the dress of a lady richly clad, says, that her robe was of 'scarlet in grain;' that is, scarlet dyed with grana, the best and most durable red dye. The import of the words 'in grain,' was afterwards changed, and the term was applied generally to all colours with which cloths were dyed, which were considered to be permanent."
"Biadetto," the artificial carbonate of copper, is said to be the blue most resembling that found in Venetian pictures. Mrs Merrifield erroneously places coal among the black pigments. It is a brown, and we know of none so useful; it is deep, but not the hot brown, such as Vandyke brown, resembling that of Teniers: Mr Eastlake has shown that it was used by the Flemish and Dutch painters. We had long used it, before we were acquainted with so authoritative a recommendation.
We find many very useful observations on oils, as to their purification, and the methods of rendering them drying. As Mrs Merrifield offers in a note a new dryer, certainly a desideratum, we quote the passage, that trials of it may be made:--
"The most powerful of all dryers is perhaps chloride of lime in a dry state: a small quantity of this, added to clarified oil, will convert it into a solid. For this reason it must be employed very cautiously: if too much be used, it may burn the brushes, and injure the colours. It has the advantage of not darkening the oil, and its drying property appears to arise from its absorbing the watery particles of the oil. Chloride of calcium is equally efficacious as a dryer, but the small quantity of iron which it contains dissolves in the oil, and darkens it. It seems probable that, if the chloride of lime were judiciously employed, it might prove serviceable as a dryer; but as I am not aware that it has been tried as such by any person but myself, the utmost caution would be required, and some experiments would be necessary, in order to ascertain the smallest possible quantity which would answer the purpose intended."