Difference between revisions of "Lead oxychloride"

Latest revision as of 13:55, 21 December 2022

Coffeepot, star motif in center contains lead oxychloride (Colonial Williamsburg Foundation 1979.808.13)

Patent Yellow Advertisement, Continental Journal, June 3, 1784, Boston

Description

A strong yellow pigment known as Patent yellow, also called Turner's yellow, Montpelier Yellow, or Mineral Yellow. The pigment is reported various sources as both lead chloride oxide and lead oxychloride. It was discovered in 1770 by chemist Karl Scheele (of Scheele's Green) who inadvertently produced it as a by-product during experiments with soda preparation. His work was not made public until 1775, when his finding was announced in a lecture by his friend and colleague, the Swedish chemist and naturalist Torbern Bergman. Although not invented by him, the technique for preparing the pigment was patented in 1781 by James Turner in England. Turner's yellow was made by mixing powdered litharge with saltwater, pouring off the alkali, then calcining the solid mass until the desired yellow was formed. This yellow pigment has a short window of use, from its introduction until the early 19th century, when it was eventually superseded by chrome yellow.

Synonyms and Related Terms

Possible lead oxychloride (Pb7O6Cl2); Reported in Eastaugh as patent yellow (PbCl2.5-7PbO); Montpelier yellow; Kassel yellow; mineral yellow; Vernona yellow; Cassel yellow (PbCl2-7PbO); Turner's yellow

Composition	PbCl2.5-7PbO and/or Pb7O6Cl2

Risks

Reportedly turns black when exposed to water, UV light and sulfur fumes.
In some examples where this pigment was identified, the paint color had the appearance of a dull brownish-yellow ochre, similar to a tarnished bronze paint without the metallic glint.

Microscopic Characteristics

In PPL, particles have a pale to medium lemon-yellow color with moderate to high relief. The particle size distribution is typically very coarse, with larger particles measuring as large as 15 microns. Smaller particles can appear shard-like, sometimes with conchoidal fracture, while larger particles can appear somewhat platy with a distinctive shallow stair-step pattern along some edges. RI > 1.662. In XPL, this pigment is reported (Eastaugh 693) as being highly birefringent with third and fourth order colors observed, but many particles have low first order birefringence, or appear dark with a yellow birefringence along the grain boundaries. Distinctively, some particles may show blue/violet interference colors.

lead oxychloride, PPL, 1000x
lead oxychloride showing anomalous violet-blues, XPL, 1000x
Patent Yellow in Dispersion, PPL, 1000x
Patent Yellow in dispersion, XPL, 1000x

Resources and Citations

Ralph Mayer, A Dictionary of Art Terms and Techniques, Harper and Row Publishers, New York, 1969 (also 1945 printing)

Susan E. Schur, Conservation Terminology: A review of Past & Current Nomenclature of Materials, Technology and Conservation, Spring (p.34-39); Summer (p.35-38); Fall (p.25-36), 1985

R.D. Harley, Artists' Pigments c. 1600-1835, Butterworth Scientific, London, 1982

R. Newman, E. Farrell, 'House Paint Pigments', Paint in America , R. Moss ed., Preservation Press, New York City, 1994

Thomas B. Brill, Light Its Interaction with Art and Antiquities, Plenum Press, New York City, 1980 Comment: first prepared in 1775

The Dictionary of Art, Grove's Dictionaries Inc., New York, 1996 Comment: "Pigments" (gives date of 1781 for patent)

Nicholas Eastaugh, Valentine Walsh, Tracey Chaplin, Ruth Siddall, Pigment Compendium, Elsevier Butterworth-Heinemann, Oxford, 2004

@@ Line 1: / Line 1: @@
 [[File:1979.808.13 coffeepot.JPG|thumb|Coffeepot, star motif in center contains lead oxychloride (Colonial Williamsburg Foundation 1979.808.13)]]
+[[File:Patent Yellow Samuel Gore.JPG|thumb|Patent Yellow Advertisement, Continental Journal, June 3, 1784, Boston]]
 == Description ==
-A strong yellow pigment that was also called Turner's yellow. Lead oxychloride was discovered in 1770 by Scheele but not patented until 1781 by J. Turner in England. Turner's yellow was made by mixing powdered lead chloride with lead carbonate then fusing. This yellow pigment was used for a short time in oil paints, but its sensitivity to light and sulfur fumes limited its use and it was replaced by chrome yellow pigments.
+A strong yellow pigment known as Patent yellow, also called Turner's yellow, Montpelier Yellow, or Mineral Yellow. The pigment is reported various sources as both lead chloride oxide and lead oxychloride.
+It was discovered in 1770 by chemist Karl Scheele (of Scheele's Green) who inadvertently produced it as a by-product during experiments with soda preparation. His work was not made public until 1775, when his finding was announced in a lecture by his friend and colleague, the Swedish chemist and naturalist Torbern Bergman. Although not invented by him, the technique for preparing the pigment was patented in 1781 by James Turner in England. Turner's yellow was made by mixing powdered litharge with saltwater, pouring off the alkali, then calcining the solid mass until the desired yellow was formed. This yellow pigment has a short window of use, from its introduction until the early 19th century, when it was eventually superseded by chrome yellow.
 == Synonyms and Related Terms ==
-hydrated lead chloride; patent yellow (PbCl2.5-7PbO); Montpelier yellow; Kassel yellow; mineral yellow; Vernona yellow; Cassel yellow (PbCl2-7PbO); Turner's yellow
+Possible lead oxychloride (Pb7O6Cl2); Reported in Eastaugh as patent yellow (PbCl2.5-7PbO); Montpelier yellow; Kassel yellow; mineral yellow; Vernona yellow; Cassel yellow (PbCl2-7PbO); Turner's yellow
 {| class="wikitable"
 |-
 ! scope="row"| Composition
-| PbCl2.5-7PbO (patent yellow)
+| PbCl2.5-7PbO and/or Pb7O6Cl2
 |}
-==Microscopic Characteristics==
+== Risks ==
-In PPL, particles have a lemon yellow color with moderate to high relief. Larger particles appear rounded while smaller particles are angular shards, sometimes with conchoidal fracture. RI > 1.662. Surfaces can appear striated. In XPL, birefringence is high with third and fourth order colors observed. Distinctively, some particles (particularly finer ones) may show blue/violet interference colors.
+* Reportedly turns black when exposed to water, UV light and sulfur fumes.
+* In some examples where this pigment was identified, the paint color had the appearance of a dull brownish-yellow ochre, similar to a tarnished bronze paint without the metallic glint.
-== Risks ==
+==Microscopic Characteristics==
-Turns black when exposed to water, UV light and sulfur fumes.
+In PPL, particles have a pale to medium lemon-yellow color with moderate to high relief. The particle size distribution is typically very coarse, with larger particles measuring as large as 15 microns. Smaller particles can appear shard-like, sometimes with conchoidal fracture, while larger particles can appear somewhat platy with a distinctive shallow stair-step pattern along some edges. RI > 1.662.
+In XPL, this pigment is reported (Eastaugh 693) as being highly birefringent with third and fourth order colors observed, but many particles have low first order birefringence, or appear dark with a yellow birefringence along the grain boundaries. Distinctively, some particles may show blue/violet interference colors.
-== Additional Images ==
 <gallery>
 File:Yellow PPL 1000x.JPG|thumb|lead oxychloride, PPL, 1000x
 File:Yellow XPL 1000x.JPG|thumb|lead oxychloride showing anomalous violet-blues, XPL, 1000x
+File:Drum patent yellow with arrows PPL 1000x.jpg|thumb|Patent Yellow in Dispersion, PPL, 1000x
+File:Drum patent yellow with arrows XPL 1000x.jpg|thumb|Patent Yellow in dispersion, XPL, 1000x
 </gallery>
 == Resources and Citations ==