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Book IX artificially coloring of metals such as gold, silver, copper

Book IX artificially coloring of metals such as gold, silver, copper Page of 251 Book IX artificially coloring of metals such as gold, silver, copper Text size:minus plus Restore normal size   Mail page  Print this page
BOOK IX
197
spatula until the entire mass is converted to verdigris. Pliny writes that some prefer to make it by triturating copper filings and vinegar in a cop­per mortar. Thus the verdigris used today is made in many ways. This is sometimes called viride aeris because of its color.
The porous verdigris is made in the following manner. One-fourth pint of strong white vinegar is poured into a copper mortar, preferably one made from Cyprian copper, and stirred with a copper pestle until it be­comes sticky. Then one-half ounce of spheroidal alum and natural salt or the whitest and most compact marine salt is added; if salt is not avail­able use a similar quantity of soda. Then, having been warmed in the sun, the mass is rubbed in the mortar until it turns green and becomes sticky from coagulation. Then, having set into a porous mass, it is laid aside. Material of good color can be made very easily by mixing one part of vinegar with two parts of old urine and using this mixture instead of vinegar. If Cyprian copper is not available the best copper obtainable should be used.
The third variety of artificial verdigris is used by goldsmiths to solder gold, as Dioscorides believed. It is prepared in a mortar of Cyprian copper into which has been poured the urine of a boy. This is stirred around with a pestle made from the same copper. Pliny has described this material under the name chrysocolla and mentioned many methods by which it is prepared. It is worth while to consider his descriptions. Goldsmiths have appropriated this material for soldering gold and all others who use it call it by this same name. The best is made from Cyprian copper and the urine of young boys to which soda is added. If it is made in a Cyprian copper mortar and rubbed with a pestle of similar material we call it santerna. When soldering argentiferous gold if a little santerna is added it makes it brighter. Cupriferous alloys are dulled and soldered with difficulty. They can be soldered however when one part of gold and seven parts of silver are added. Today goldsmiths use a substitute they call borax (borax) more often than chrysocolla. This is made from soda, as I have said in Book III, and contains no verdigris.
Caeruleum is also produced in different ways although the finest is prepared in the following manner. Three pounds of very strong vinegar is poured into an oak vesssel together with a pound of powdered artificial sal ammoniac. The latter is dissolved and a small staff fastened upright in the center of the vessel. From this staff sheets of silver full of small slits are suspended so that they do not touch the vinegar solution. Before suspending them the slits are first smeared with quicksilver. The vessel is covered with a lid and sealed so that there are no air holes. It is then covered with dung or placed in a trench and covered with earth. After twenty days the vessel is opened and the material that has collected like rust on the silver sheets is scraped off and the vessel is again covered and left for twenty days. This procedure is followed until the silver is entirely eaten away and then new sheets are suspended in the vessel. The material
Book IX artificially coloring of metals such as gold, silver, copper Page of 251 Book IX artificially coloring of metals such as gold, silver, copper
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