Stack Process Lead White

Rublev Colours Stack Process White Lead is made in small amounts according to 16th century Dutch method, differing little to the historical “stack process.” It is basic carbonate of lead and usually contains about 70% of lead carbonate and 30% of lead hydroxide. This grade of white lead is composed of the actual flakes that fall off the corroded lead coils of the stack process and the white lead that is mechanically removed. It is washed and ground ready to be mixed with a paint binder.

Rublev Colours Stack Process White Lead is ground to about the same granularity typically found in old masters’ paintings. The pigment is available from Natural Pigments as small round cakes, weighing about 30 to 40 grams each. The small cakes are friable and are easily broken apart and ground in a paint vehicle or in water. We recommend to first crush the cake in a mortar with a pestle, adding a small amount of vehicle or water to avoid raising dust, and then scoop the mixture onto a flat surface to further grind with a muller.


Origin and History
Lead white is the most important of all lead pigments. Not overlooking special uses of lime white in wall painting, it is safe to say that, historically, it is the most important of all white pigments. It was the only white pigment used in European easel painting until the 19th century. It has been produced since early historical times. Theophrastus, Pliny, and Vitruvius all described its preparation from metallic lead and vinegar. It is one of the oldest synthetically produced pigments.

Source
There are numerous methods for making lead white, but all historical methods differ little from the old Dutch method. The Dutch method, otherwise known as the “stack process,” essentially consists of exposing metallic lead in the form of strips for about three months in earthenware pots, which have a separate compartment in the bottom containing a weak solution of acetic acid (vinegar). The pots are stacked in tiers over a layer of horse manure in a shed. After the shed is closed, the combined action of the acetic acid vapors, heat and carbon dioxide from the fermenting manure, carbon dioxide in the air and water vapor slowly transforms the lead to basic lead carbonate.

Rublev Colours Stack Process White Lead is made according to this manner in a carefully controlled environment to duplicate the method used by the 16th century Dutch and to ensure the purity of the pigment. It is thoroughly washed to remove impurities and ground. Rublev Colours Stack Process White Lead is a warm white of crystalline particles that vary greatly in size and shape than the finely-divided modern lead white available today.

Permanence and Compatibility
Despite lead white being a carbonate, and hence sensitive to acids, it has an excellent record for permanence. It is unaffected by light. When applied in watercolor technique, however, traces of hydrogen sulfide in the air may cause it to turn black. Although lead white is theoretically incompatible with sulfide pigments, and should form black lead sulfide in contact with them, no examples are readily known. There might be some doubt, however, about mixing orpiment and realgar with lead white, although some identified cases show no discoloration.

Oil Absorption and Grinding
A special feature of lead white is its low oil-absorption rate. According to most sources it requires only 8 to 15 grams of oil to make a workable paste with 100 grams of lead white pigment. Stack white lead requires even less oil to make a stiff paste than modern lead whites. It can be used with aqueous media, such as egg tempera, casein and animal glue (distemper). It can also be used in encaustic (wax) technique, but does not perform well in true fresco technique.

Toxicity
Lead white is toxic if inhaled as a dust or if ingested. Grinding and making the pigment into paint is hazardous and the sale of lead compounds in several countries has been prohibited. Painters may suffer from “painters’ colic” or “plumbism,” if they are careless in using it. Extreme care should be used in handling the dry powder pigment so as not to inhale the dust. Clean all surfaces after working with the pigment to avoid contamination. Do not smoke, eat or drink while using the pigment in any form, including in paint. Be sure and read the cautionary statements contained in the Material Safety Data Sheet (MSDS) referenced below.


[FONT=tahoma][COLOR=#777777]Rublev Colours Pigment: Stack Process White Lead (Dutch Method)[/COLOR][/FONT]


Read cautions about handling pigments

Read the Material Safety Data Sheet (MSDS) for this Product