CHAPTER VI
MARBLE FOR USE IN STUCCO
Marble is not produced everywhere of the same kind. In some places the lumps are found to contain transparent grains like salt, and this kind when crushed and ground is extremely serviceable in stucco work. In places where this is not found, the broken bits of marble or "chips," as they are called, which marble-workers throw down as they work, may be crushed and ground and used in stucco after being sifted. In still other places--for example, on the borderland of Magnesia and Ephesus--there are places where it can be dug out all ready to use, without the need of grinding or sifting, but as fine as any that is crushed and sifted by hand.
CHAPTER VII
NATURAL COLOURS
As for colours, some are natural products found in fixed places, and dug up there, while others are artificial compounds of different substances treated and mixed in proper proportions so as to be equally serviceable.
1. We shall first set forth the natural colours that are dug up as such, like yellow ochre, which is termed [Greek: ochra] in Greek. This is found in many places, including Italy, but Attic, which was the best, is not now to be had because in the times when there were slaves in the Athenian silver mines, they would dig galleries underground in order to find the silver. Whenever a vein of ochre was found there, they would follow it up like silver, and so the ancients had a fine supply of it to use in the polished finishings of their stucco work.
2. Red earths are found in abundance in many places, but the best in only a few, for instance at Sinope in Pontus, in Egypt, in the Balearic islands of Spain, as well as in Lemnos, an island the enjoyment of whose revenues the Senate and Roman people granted to the Athenians.
3. Paraetonium white gets its name from the place where it is dug up.
The same is the case with Melian white, because there is said to be a mine of it in Melos, one of the islands of the Cyclades.
4. Green chalk is found in numerous places, but the best at Smyrna. The Greeks call it [Greek: theodoteion], because this kind of chalk was first found on the estate of a person named Theodotus.
5. Orpiment, which is termed [Greek: a.r.s.enikon] in Greek, is dug up in Pontus. Sandarach, in many places, but the best is mined in Pontus close by the river Hypanis.
CHAPTER VIII
CINNABAR AND QUICKSILVER
1. I shall now proceed to explain the nature of cinnabar. It is said that it was first found in the Cilbian country belonging to Ephesus, and both it and its properties are certainly very strange. First, before getting to the vermilion itself by methods of treatment, they dig out what is called the clod, an ore like iron, but rather of a reddish colour and covered with a red dust. During the digging it sheds, under the blows of the tools, tear after tear of quicksilver, which is at once gathered up by the diggers.
2. When these clods have been collected, they are so full of moisture that they are thrown into an oven in the laboratory to dry, and the fumes that are sent up from them by the heat of the fire settle down on the floor of the oven, and are found to be quicksilver. When the clods are taken out, the drops which remain are so small that they cannot be gathered up, but they are swept into a vessel of water, and there they run together and combine into one. Four pints of it, when measured and weighed, will be found to be one hundred pounds.
3. If the quicksilver is poured into a vessel, and a stone weighing one hundred pounds is laid upon it, the stone swims on the surface, and cannot depress the liquid, nor break through, nor separate it. If we remove the hundred pound weight, and put on a scruple of gold, it will not swim, but will sink to the bottom of its own accord. Hence, it is undeniable that the gravity of a substance depends not on the amount of its weight, but on its nature.
4. Quicksilver is a useful thing for many purposes. For instance, neither silver nor copper can be gilded properly without it. And when gold has been woven into a garment, and the garment becomes worn out with age so that it is no longer respectable to use, the pieces of cloth are put into earthen pots, and burned up over a fire. The ashes are then thrown into water and quicksilver added thereto. This attracts all the bits of gold, and makes them combine with itself. The water is then poured off, and the rest emptied into a cloth and squeezed in the hands, whereupon the quicksilver, being a liquid, escapes through the loose texture of the cloth, but the gold, which has been brought together by the squeezing, is found inside in a pure state.
CHAPTER IX
CINNABAR (_continued_)
1. I will now return to the preparation of vermilion. When the lumps of ore are dry, they are crushed in iron mortars, and repeatedly washed and heated until the impurities are gone, and the colours come. When the cinnabar has given up its quicksilver, and thus lost the natural virtues that it previously had, it becomes soft in quality and its powers are feeble.
2. Hence, though it keeps its colour perfectly when applied in the polished stucco finish of closed apartments, yet in open apartments, such as peristyles or exedrae or other places of the sort, where the bright rays of the sun and moon can penetrate, it is spoiled by contact with them, loses the strength of its colour, and turns black. Among many others, the secretary Faberius, who wished to have his house on the Aventine finished in elegant style, applied vermilion to all the walls of the peristyle; but after thirty days they turned to an ugly and mottled colour. He therefore made a contract to have other colours applied instead of vermilion.
3. But anybody who is more particular, and who wants a polished finish of vermilion that will keep its proper colour, should, after the wall has been polished and is dry, apply with a brush Pontic wax melted over a fire and mixed with a little oil; then after this he should bring the wax to a sweat by warming it and the wall at close quarters with charcoal enclosed in an iron vessel; and finally he should smooth it all off by rubbing it down with a wax candle and clean linen cloths, just as naked marble statues are treated.
4. This process is termed [Greek: ganosis] in Greek. The protecting coat of Pontic wax prevents the light of the moon and the rays of the sun from licking up and drawing the colour out of such polished finishing.
The manufactories which were once at the mines of the Ephesians have now been transferred to Rome, because this kind of ore was later discovered in Spain. The clods are brought from the mines there, and treated in Rome by public contractors. These manufactories are between the temples of Flora and Quirinus.
5. Cinnabar is adulterated by mixing lime with it. Hence, one will have to proceed as follows, if one wishes to prove that it is unadulterated.
Take an iron plate, put the cinnabar upon it, and lay it on the fire until the plate gets red hot. When the glowing heat makes the colour change and turn black, remove the plate from the fire, and if the cinnabar when cooled returns to its former colour, it will be proved to be unadulterated; but if it keeps the black colour, it will show that it has been adulterated.
6. I have now said all that I could think of about cinnabar. Malachite green is brought from Macedonia, and is dug up in the neighbourhood of copper mines. The names Armenian blue and India ink show in what places these substances are found.
CHAPTER X
ARTIFICIAL COLOURS. BLACK
1. I shall now pa.s.s to those substances which by artificial treatment are made to change their composition, and to take on the properties of colours; and first I shall treat of black, the use of which is indispensable in many works, in order that the fixed technical methods for the preparation of that compound may be known.
2. A place is built like a Laconic.u.m, and nicely finished in marble, smoothly polished. In front of it, a small furnace is constructed with vents into the Laconic.u.m, and with a stokehole that can be very carefully closed to prevent the flames from escaping and being wasted.
Resin is placed in the furnace. The force of the fire in burning it compels it to give out soot into the Laconic.u.m through the vents, and the soot sticks to the walls and the curved vaulting. It is gathered from them, and some of it is mixed and worked with gum for use as writing ink, while the rest is mixed with size, and used on walls by fresco painters.
3. But if these facilities are not at hand, we must meet the exigency as follows, so that the work may not be hindered by tedious delay. Burn shavings and splinters of pitch pine, and when they turn to charcoal, put them out, and pound them in a mortar with size. This will make a pretty black for fresco painting.
4. Again, if the lees of wine are dried and roasted in an oven, and then ground up with size and applied to a wall, the result will be a colour even more delightful than ordinary black; and the better the wine of which it is made, the better imitation it will give, not only of the colour of ordinary black, but even of that of India ink.
CHAPTER XI
BLUE. BURNT OCHRE
1. Methods of making blue were first discovered in Alexandria, and afterwards Vestorius set up the making of it at Puzzuoli. The method of obtaining it from the substances of which it has been found to consist, is strange enough. Sand and the flowers of natron are brayed together so finely that the product is like meal, and copper is grated by means of coa.r.s.e files over the mixture, like sawdust, to form a conglomerate.
Then it is made into b.a.l.l.s by rolling it in the hands and thus bound together for drying. The dry b.a.l.l.s are put in an earthern jar, and the jars in an oven. As soon as the copper and the sand grow hot and unite under the intensity of the fire, they mutually receive each other"s sweat, relinquishing their peculiar qualities, and having lost their properties through the intensity of the fire, they are reduced to a blue colour.
2. Burnt ochre, which is very serviceable in stucco work, is made as follows. A clod of good yellow ochre is heated to a glow on a fire. It is then quenched in vinegar, and the result is a purple colour.