[Pigments and Binders]

Lead-tin Yellow

Pigment Name/Synonyms/Pigment Code

This picture shows the pigment lead-tin yellow mixed with three different binders. From left to right in the containers they are; egg-tempera, gum-arabic, and linseed oil. At the bottom of the picture there are samples of lead-tin yellow mixed with other pigments. On the right is a color scale to compare the pigment and mixtures against.

 

What is now commonly called lead-tin yellow has had several different names in the past. Italian manuscripts have described a color, giallolino, which is identical to lead-tin yellow. In northern parts of England the terms massicot and general were used to describe the same pigment. The current name lead-tin yellow is self explanatory. It is a result of the components of the pigment lead and tin which combine to form a yellow hue. The official pigment code designation is 77577.

 

History of Use by Artists

Lead-tin yellow is a very old pigment that can be dated back to as early as 1300 in Medieval Europe. All of the paintings that have been identified as containing lead-tin yellow date between approximately 1300 and 1750. This hue was used most frequently in the 15th, 16th, and 17th centuries. One of the most important uses of lead-tin yellow pigment was in the color glass production in Venice and Bologna in the Middle Ages. It was used widely in Western Europe in frescoes and panels. Many paintings from the fifteenth, sixteenth and seventeenth centuries appear to have some of this color. As Daniel Thompson mentions in his book The Materials and Techniques of Medieval Painting, this pigment was used to make "greens lighter, without making them "sagey" (Thompson 180). The first half of the 18th century saw a decline in the use of the pigment, and in the mid to late 18th century the use of the pigment came to an end. The cause of the abrupt end of the pigment is not clear. Since we know that lead-tin yellow was not used historically after the year 1750 this allows historians and experts to recognize any forgeries of paintings from this time period, assuming the impostor used the exact pigment.

In 1940 a man named Jacobi rediscovered the pigment, lead-tin yellow. He was working at the Doerner Institute in Munich when he rediscovered the pigment. He was, "carrying out emission spectrometric investigations of samples from paintings, and subsequently it was synthesized in the laboratory" (Roy 85). Jacobi's attention was drawn to the pigment because it contained not only high levels of lead, but also tin. This was an unusual and unknown combination because it had not been used since approximately 1750. Previous tests of the lead-tin pigment were done only to detect the lead content, and therefore it was not known that there was another element, tin, in the compound.

After it was discovered that a pigment made of a lead-tin combination existed, tests were run on numerous paintings to determine if it had been used. It was then discovered that not only was it used frequently in European paintings, but that there were two forms of the pigment. There is a lead-tin yellow type I and a lead-tin yellow type II. The most common form was type I. It is made of a lead-tin oxide known as

Pb₂SnO₄ (Roy 83). Type II is the earlier pigment of the two different types. It is made of another variety of lead-tin oxide which may also contain free tin oxide and silicon as well.

Source/Preparation of Pigment

Type I can be made by heating lead and tin to very high temperatures. One must add three parts of lead, either lead monoxide, minimum, or lead dioxide, to one part tin oxide to form type I pigment (Roy 89). To obtain a warmer yellow hue, the temperature should be between 650 and 700 degrees Celsius. In order to achieve a more lemon hue, the temperature must be between 720 and 800 degrees Celsius (Roy 91).

Type II can be made by means of a yellow lead glass that will begin to melt at a temperature of 500 degrees Celsius. Once the temperature is raised to between 900 and 950 degrees Celsius, an "intense yellow glass mass forms" (Roy 91). Once this mass is pulverized, a lemon-yellow hue similar to that of the lead-tin yellow type I at a temperature of 720 to 800 degrees Celsius is formed. It can also be formed by adding silica to a pre-made substance of Pb₂SnO₄ which then must be heated to between 800 and 950 degrees Celsius.

Chemistry of the Pigment

Pb₂SnO₄

Lead-tin yellow pigment decomposes very slowly even when boiling with very concentrated acids. This pigment can be used in lime medium, because it is not affected by alkalis. Soluble sulfides cause darkening of the pigment with formation of lead sulfide. As mentioned earlier, when heated to more than 900 degrees Celsius, the pigment decomposes and the amount of tin oxide increases.

Binders

Lead-tin yellow pigment is not affected by light. Different experiments prove that even combined with different binders, it still lacks reaction to light. That is why it is used instead of lead monoxide in some reactions. This binder has been observed in many European paintings in oil and tempera media, as well as in combination with lime, and no alternation in the color has been noticed.

The table bellow shows the mass of the pigment used and also the binder with which it was combined. Those values have been experimentally found in a lab experiment. The results from those combinations of pigment and different binders are explained in the next paragraph.

Sample	Mass/grams	Weighing Boat	Binder
A	1.725	medium size	water color-12 drops
B	1.756	medium size	linseed oil-17 drops
C	1.901	large size	egg tempera-9 drops

As the experiment proves lead-tin yellow pigment dissolves very well in linseed oil and it becomes a smooth homogeneous substance. However, in pure aqueous media, or in gum arabic used in lab, the formation of lead sulfide is possible and the substance is not as even as the one mixed with oil. The pigment does not mix well with egg-tempera either. The mixture of the two substances has some granules of the pigment, which are not dissolved very well in the binder and it takes a long time to make the compound smooth.

Although the lead-tin yellow pigment dissolves very slowly in egg-tempera binder, it is a very good pigment, which is very stable and does not go off the surface easily. The only bad thing about the pigment is that it dries quickly and cannot be produced in a large amount at once. The combination between gum arabic and the pigment is the worst one, because the final compound is not even, it dries fast, and when it is completely dried the pigment goes off the surface. The pigment is unstable and it flakes, powders and crumbles. The best binding media for lead-tin oil is linseed oil. The mixture is smooth, it sticks very well to the surface and it is hard to remove it even with sharp object. The best characteristic is that the oil pigment dries very slowly, and it is easy to work with it.

Optical characteristics: Looking through the microscope

Lead-tin yellow particles can be distinguished with the help of an optical microscope. They are very small particles and almost all of them are similar in form-"sharp-edged conchoidal fractures" (Roy 91) or particles with crystalline form. The difference between the particles, as measured in lab, is between 6 and 60nm. With a lower objective of the microscope, it is almost impossible to recognize separated particles. Even with a higher objective the image is not very clear.

Using transmitted light from the microscope, yellow refracting transparent particles are observed. The particles from one of the types of lead-tin yellow have tetragonal form and the particles from the other type have "cubic pyrochlore-type crystal structure and are isotropic" (Roy 91). The cubic particles make the first type of pigment birefracting, but because they have very intense color, the interfering colors cannot be observed. The best results in observing lead-tin yellow are received when incident light is used. Observed with an Olympus microscope using an incident light, the real color of the particles can be distinguished.

Health Issues

Lead-tin yellow is known to have toxic effects and cause poisoning. The reason for this toxicity is that it contains lead, which is dangerous for human beings. Lead oxide, lead monoxide and some other lead compounds even at relatively small amounts can cause coma and death. Both males and females are equally endangered, especially when they are chronically exposed to this chemical element. The most common effects are anemia, and nervous system and kidney problems. It is thought that lead is carcinogenic and it can also affect the birth process, which means that it is hazardous for the reproductive system and sometimes results in infertility. If pregnant women are exposed to lead compounds for longer periods, this may result in hazardous forced abortions and other complications.

Tin oxides and chlorides are also hazardous for the human health, but they are not fatal. They usually cause skin, respiratory and eye irritation. Children are easier and more seriously affected by the lead and tin compounds in much smaller amounts. Because of the danger from poisoning, nowadays lead containing colors are prohibited in wall paints, but they are still used in automobile paints and some of the artists' paints.

Links to other Web sites:

There are some links, which show paintings in which lead-tin yellow was used.

Madonna and Child with the Young St. John the Baptist-Michele Tosini(1503-1577)


Joseph Reveals His Dreams to His Brothers-Raffaello Santi (1483-1520)

View of Delft-Johannes Vermeer

Click here to find about an interesting research in pigments and archaerometric analysis

Linda Millikan, Doriana Basamakova. 1998