-is now used in
preparing pigments for painting sails for the British navy. It is also
used in the manufacture of printing-ink; and we have now Cennino's
authority for using it with _blue_ pigments. Sir Humphrey Davy informs
us, that the Vestorian or Egyptian azure, the excellence of which is
proved by its duration of 1700 years, may be easily imitated by
carbonate of soda, opaque flint, and copper filings. The translator has
made many experiments on the effect of the alkalis and neutral salts
when mixed with colours, and has every reason to be satisfied with the
addition of soda, when properly used." We have not ourselves tried
sufficiently soda with oil, and have suspected it would not have the
effect of rendering the paint hard; but that borax does render the paint
very hard we have abundant proof. We have subjected a picture painted
with it to the razor to scrape it down, and could with difficulty
succeed, though the picture had not been long painted; and we have
rolled together masses of paint so mixed, and they have been thought by
persons into whose hands we have put them, stone. We have heard artists,
who have tried this mixture of borax and oil, declare it had the
contrary effect; but, on enquiry, found that they procured the vehicle
from colour-makers, who sold them, we have good grounds for believing, a
mixture of their own, in which, if borax formed any part, mastic varnish
formed a much larger. Among our papers we found one sent us by Dr
Rainier; we were not chemists enough to make it intelligible, and for
that recipe which we give in a note,[6] we are indebted to our friend
Mr C. T. Coathupe of Bristol, on whose chemical and general scientific
knowledge we have great reliance, and who much confirmed our view, or
rather Rainier's, of the advantage of rendering the oils saponaceous by
the means of borax. In consequence of our communication with him, Mr
Coathupe published in the _Art Union_ one or two very valuable papers in
1842. In speaking of this vehicle we do so the more boldly as it is not
our own, nor do we claim the least merit on account of it; it is solely
the discovery, or re-discovery, be it which it may, of our ever valued
friend Rainier, now no more. Without saying that it is or is not _the_
old one, "che tutti i pittori del mondo aveano lungamente desiderata,"
we do not hesitate to say that it is a good one, and does obviate those
"oily appearances so disagreeable to the eye"; and we are the more