DOI Page / Citation link:
https://doi.org/10.11588/diglit.62783#0047
IN FRESCO PAINTING.
xxxvii
Puteoli. The manner of making it, and the ingredients of which it
is composed, are rather remarkable. Sand is ground up so fine with
flour of nitre, as almost to resemble wheat flour, and being mixed with
copper filings, made with a coarse file like a rasp, the whole is
sprinkled with water, that it may adhere together. It is then made
into balls, by working it with the hands, and these balls are laid
aside to dry. When dry, they are put into an earthen jar and the
jar is put into the fire. And then, when the copper and the sand
have united, boiling together by the vehemence of the fire, giving
and receiving vapours from each other, they lose their own proper-
ties, and being united altogether by the force of the fire, they be-
come of a blue colour.
“ Similarly, on account of the scarcity of the colour Indigo, they
make an imitation of that colour by mixing Selinusian or Anularian
chalk, with the glass, which the Greeks call vaXov (hydlon)
Sir Humphrey Davy observes,3 “ That this colour can be
easily and cheaply made. I find that fifteen parts by weight of
carbonate of soda, twenty parts of powdered opaque flint, and three
parts of copper filings, strongly heated together for two hours, gave
a substance of exactly the same tint, and nearly the same degree of
fusibility, and which, when powdered, produced a fine deep blue.”
The ingredients meant by Sir H. Davy, are nearly the same as
those mentioned by Vitruvius, except that the latter mentions nitre,
instead of carbonate of soda, and sand instead of flint, the difference
in the latter, being merely nominal, since pure sand consists of silica
almost in the state of powder, and flint also consists of silica in a con-
solidated form. Volumes have been written to ascertain what the
nitre of the ancients really was, but the inquiry is unnecessary here.
It is sufficient for our purpose to shew that the Vestorian Azure was
a blue glass. I think I shall be able to prove that the blue pigment
used in Italy and Spain during the latter half of the 16th
century, and the whole of the 17 th and 18th centuries, was of the
same nature as this Vestorian Azure.
Bald. Orsini, the Translator of Vitruvius (Ed. of 1802), speak-
ing of the Vestorianum, says, “ this glass is synonymous with what
a On the Colours used by the Ancients.—Phil. Trans. 1815. See also Chap-
tal’s “ La Chimie appliquee aux Arts.”
xxxvii
Puteoli. The manner of making it, and the ingredients of which it
is composed, are rather remarkable. Sand is ground up so fine with
flour of nitre, as almost to resemble wheat flour, and being mixed with
copper filings, made with a coarse file like a rasp, the whole is
sprinkled with water, that it may adhere together. It is then made
into balls, by working it with the hands, and these balls are laid
aside to dry. When dry, they are put into an earthen jar and the
jar is put into the fire. And then, when the copper and the sand
have united, boiling together by the vehemence of the fire, giving
and receiving vapours from each other, they lose their own proper-
ties, and being united altogether by the force of the fire, they be-
come of a blue colour.
“ Similarly, on account of the scarcity of the colour Indigo, they
make an imitation of that colour by mixing Selinusian or Anularian
chalk, with the glass, which the Greeks call vaXov (hydlon)
Sir Humphrey Davy observes,3 “ That this colour can be
easily and cheaply made. I find that fifteen parts by weight of
carbonate of soda, twenty parts of powdered opaque flint, and three
parts of copper filings, strongly heated together for two hours, gave
a substance of exactly the same tint, and nearly the same degree of
fusibility, and which, when powdered, produced a fine deep blue.”
The ingredients meant by Sir H. Davy, are nearly the same as
those mentioned by Vitruvius, except that the latter mentions nitre,
instead of carbonate of soda, and sand instead of flint, the difference
in the latter, being merely nominal, since pure sand consists of silica
almost in the state of powder, and flint also consists of silica in a con-
solidated form. Volumes have been written to ascertain what the
nitre of the ancients really was, but the inquiry is unnecessary here.
It is sufficient for our purpose to shew that the Vestorian Azure was
a blue glass. I think I shall be able to prove that the blue pigment
used in Italy and Spain during the latter half of the 16th
century, and the whole of the 17 th and 18th centuries, was of the
same nature as this Vestorian Azure.
Bald. Orsini, the Translator of Vitruvius (Ed. of 1802), speak-
ing of the Vestorianum, says, “ this glass is synonymous with what
a On the Colours used by the Ancients.—Phil. Trans. 1815. See also Chap-
tal’s “ La Chimie appliquee aux Arts.”