418 Experiments and Olservat'ions 



Aklobrandini picture, are all produced by mixtures of ochres 

 with blacks. Those in the Aklobrandini picture yield oxide of 

 iron to muriatic acid, but the darker shades were not touched 

 by tliat acid, nor by solution of alkalies. 



VIII. Of the JVhites of the Ancients. 



The white colours in the Aldobrandini picture are soluble in 

 acids with effervescence, and have the characters of carbonate 

 of lime. 



The principal white in the vase of mixed colours appears to be 

 a very fine chalk. There is another white with a tint of cream 

 colour, which is a fitie aluminous clav. 



The whites that I have examined from the baths of Titus, and 

 those from other ruins, are all of the same kind. 



I have not met witl^ ceruse amongst the ancient colours, 

 thougli we know from Theophrastus, Vitruvius, and Pliny, that 

 it was a common colour: and Mtruvius describes it as made by 

 the action of lead upon vinegar. 



Several white clays are mentioned by Pliny as emploved in 

 pointing, of which the Parastonium was considered as affording 

 the finest colour. 



IX. Of the Manner in tvhich iheAncieiits applied their Colours. 



It appears from Vitruvius that the colours used in fiesco paint- 

 ing were applied moist to the surface of a stucco* formed of 

 powdered marble cemented by lime; he states that the wall or 

 ceiling had three distinct coatings of stucco made of this material, 

 of which the first contained coaise powder of marble, the second 

 the finer powder, and the third the finest powder of all, and that 

 aftcv this the wall was polished before the colour was applied. 

 The stuccos that remain in the ruins of the baths of Titus and 

 Livia are of this kind, and so is the ground of the Aldobrandini 

 jMcture ; tliey are beautifully white, and almost as hard as mar- 

 ble, and the graiuilar marble of different degrees of fineness may 

 be distinguished in them. This circumstance indeed offers a 

 test of the anti([uity of ruins at Rome. In the houses that have 

 been built in the middle and later ages, decomposing lava has 

 been mixed with the calcareous cement in<5tead of granular mar- 

 ble, and the stuccos of these houses are gray or brown, and very 

 coarse in their texture. 



Pliny says that purple, orpiment, ceruse, the natural azure, 

 indigo, and the meline white, were injured by application to wet 

 stucco, which is easily explained in the case of orpiment, car- 

 bonate of copper, ceruse, and indigo, from their chemical com- 

 position. 



* Lib. vii, cap. 2, 3, & 4. ^ 



Vitruvius 



