425 
PIGMENT. 
kind of pit-coal. It appears, therefore, that the differ¬ 
ences of foots do not depend altogether on the qualities 
of the fubje&s, but in a great meafure on the manner 
in which the fubjedil is burnt, or the foot caught. The 
foots produced in common chimneys, from different 
kinds of wood, refin'ous and not relinous, dry and green, 
do not differ near fo much from one another, as thofe 
which are produced from one kind of wood in a common 
chimney, and in the confined way of burning above- 
mentioned.” 
Ivory-black is prepared from ivory or bones burnt in 
a clofe veffel. This, when finely ground, forms a more 
beautiful and deeper colour than lamp-black; but, in the 
common methods of manufacturing, it is fo much adul¬ 
terated with charcoal-duft, and fo grofsly levigated, as to 
be unfit for life. An opaque deep black for water¬ 
colours, is made by grinding ivory-black with gum-water, 
or with the liquor which fettles from the whites of eggs 
after they have been buffered to (land a little. Some ufe 
gum-water and the whites of eggs together; and report, 
that a fmall addition of the latter makes the mixture flow 
more freely from the pencil, and improves its gloflinefs. 
It may be obferved however, that, though ivory-black 
makes tbedeepeft colour in wateras well as in oil-painting, 
yet it is not on this account always to be preferred to 
other black pigments. A deep jet-black colour is feldoni 
wanted in painting; and in the lighter fhades, whether 
obtained by diluting the black with white bodies, or by 
applying it thin on a white ground, the particular beauty 
of the ivory-black is in a great meafure loft. 
Blue-black is faid to be prepared from the burnt ftalks 
and tendrils of the vine. Thefe, however, the colour- 
makers feldom give themfelves the trouble of procuring, 
but lubilituje in its place a mixture of ivory-black and 
the common blue ufed for clothes. 
Indian-ink is an excellent black for water-colours. It 
hath been difcovered by Dr. Lewis to conliftofa mixture 
of lamp-black and common glue. Ivory-black, or char¬ 
coal, he found to anfwer equally well, provided they were 
levigated to a fufficient degree of finenefs, which indeed 
requires no fmall trouble. 
z. White —The white colours commonly to be met with 
are, white-flake, white-lead, calcined hartfnorn, pearl- 
white, Spanifh-vvhite, egg-fhell-white, and nitrate of bif- 
muth. The flake-white and white-lead are properly the 
fame. The preparation of the former is kept a fecret; 
the method of preparing the latter is defcribed under 
Chemistry. Thefe are the only whites that can be 
ufed in oil, all the reft being tranfparent unlefs they are 
laid on with water. Calcined hartlhorn is the moft ufeful 
of the earthy whites, as being the leaf! alkaline. Spanifh 
white is nothing but finely-prepared chalk. Pearl-white 
is made from oyfter-fhells ; and egg-lhell white from the 
fhells of eggs. All thefe, by their attrailion for acids, 
»nlift neceifarily deftroy fuch colours as have any acid or 
metallic fait in their compofition. The nitrate of bifmuth 
is apt to turn biack, as are alfo flake-white and white-lead, 
when ufed in water. The white precipitate of lead re¬ 
commended under Chemistry, is greatly fuperior as a 
water-colour to all thefe, being perfectly free from any 
alkaline quality, and not at all apt to lofe its own colour, 
or to injure that of other fubftances. It is a carbonate 
of lead. 
Mr. Kemp, in the Philofophical Journal, voi. xxx. 
relates fome particulars of the mode of preparing a white 
colour, for water-painting, from barytes; of which the 
bare fail that it had been effected, was before made public 
by Mr. Hume, without any ftatement of the method ufed 
for its production. Mr. Kemp’s procefs is as follow's: 
Pure barytes, or the common mild carbonate, is to be 
diflolved in diluted nitro-muriatic acid; and to the 
filtered folution as much. carbonate of ammonia is to be 
added, as will precipitate all the barytes; which may be 
ieparated by filtration, and, after repeated wafliings with 
filtered water, is to be gradually dried by the heat of the 
Vol. XX. No. 1379. 
fun or a fire; and rubbed into a fine powder, or made 
into cakes for ufe. Pure ammonia was tried to precipi¬ 
tate the barytes, but the colour produced was not near 
fo white as that obtained by the carbonate. Mr. Kemp 
Hates, that an artift of acknowledged celebrity, who has 
ufed this white, fpeaks very favourably of it. 
Barytes has long been ufed in the preparation of the 
common white-lead of commerce in Germany ; it is added 
to make the white-lead cover the work better, and to 
leflen the price. The fa< 5 l of its being ufed as above 
mentioned, confirms Mr. Kemp’s and Mr. Hume’s opi¬ 
nion of its value as a pigment; for, though the preparation 
of it ufed in the two cafes is not the fame, that ufed with 
the white lead being the fulphate of barytes, there can be 
little doubt but that the carbonate is equal, if not fupe¬ 
rior, to the other, there being many inftances of metallic 
and other carbonates being ufeful as pigments, and not 
one of a fulphate being fo but that ftated. 
3. Red. —The red colours ufed in painting are of two 
forts, viz. thofe which incline to the purple, and fuch 
as are of a full fcarlet, and tend rather to the orange. 
The firft are carmine, lake, rofe-pink, red-ochre, and 
Venetian-red. The fecond are vermilion, red-lead, fcar- 
let-ochre, common Indian-red, Spanilh-brown, and terra 
di Sienna, burnt. 
We have already laid down fome general rules for the 
preparation of carmine and lake. Particular receipts 
have been delivered with the greateft confidence for 
making thefe fine colours ; but all of them muft necefla- 
rily prove ineffectual, becaufe an earthy balls,is recom¬ 
mended for ftriking the colour upon. From the princi¬ 
ples of chemirtry, however, we are certain, that if nitric 
acid, or folution of tin, is made ufe of for brightening a 
colour made with any earthy bafis, it muft infallibly be 
deftroyed by that bafis, by reafon of its alkaline quality. 
Carmine is the brighteft and moft beautiful red colour 
known at prefent: the belt comes from France. Lake 
differs from it in being capable of mixture with oil, 
which carmine is not, unlefs with great difficulty. The 
former is alfo much more inclined to purple than carmine. 
This laft quality, however, is reckoned a defeat; and 
accordingly, the more that lake approaches to the fcarlet 
or true crimfon, the more it is valued. On dropping 
folution of tin into an aqueous tinCture of brazil-wood, 
a beautiful precipitate falls, of a purplifli crimfon colour. 
This may be very well fubftituted in place of the dearer 
lakes on many occafions. 
Rofe-pink is a very beautiful colour, inclining more to 
the purple than fcarlet. The earth, or bafis, is principally 
chalk, and the tinging fubllance is extracted from Brafii 
or Campeachy wood. This pigment, which does not 
Hand, is feldom employed, except for the coarfe work of 
houfe-painters, or for paper-hangings, and fometimes 
with varnifii. It may be prepared by boiling fix pounds 
of Brafii wood, or three pounds of Brafii and three of 
Campeachy wood, in three gallons of water in which a 
quarter of a pound of alum has been diflolved, for an 
hour. Purify the fluid, by draining through flannel, and 
put back the wood into the boiler with the fame quantity 
of alum, and proceed as before; repeating tbe operation 
a third time; mix the three quantities of tinCture toge¬ 
ther, and evaporate them till only two quarts of fluid 
remain. Prepare eight pounds of chalk, by walking it 
over in water, in which a pound of alum has been diflolved, 
and afterwards fufing the chalk from the fait formed by 
the alum, and drying it to" the confidence of a ftiff clay. 
Grind the chalk and tincture together ; and lay the mafs 
to dry out of the fun or cold air. The goodnefs of rofe- 
pink confifts chiefly in the brightnefs of the colour, and 
finenefs of its fubllance. 
Red ochre and Venetian red differ in nothing from the 
colcothar of vitriol well calcined. The oxydes of iron 
may be made to appear either purplifli, or inclining to 
fcarlet, according to the manner in which the calcination 
is performed. If the matter is perfectly deprived of its 
5 Q phlogifton*. 
