Graduation Year

2019

Document Type

Campus Only Senior Thesis

Degree Name

Bachelor of Arts

Department

Art Conservation

Reader 1

Nancy Williams

Reader 2

Eric Doehne

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Abstract

One of the most stunning works of art on the Scripps College campus is the mural Flower Vendors(1946). The artist,Alfredo Ramos Martínez, an influential figure in Mexican Modernism, executed the work using a variety of traditional and non-traditional techniques. Prior analysis of the work indicated the use of a wax emulsion medium and established the range of pigments used. Ramos Martínez’s use of lead chromate (chrome yellow, Pb(CrO4)) was unusual in wall painting, and the pigment itself has been shown to photodegrade and darken over time in oil paintings, due to the reduction of Cr(VI) to Cr(III). The Pb(CrO4) in Flower Vendorsdoes not appear to have darkened, raising questions about the stability of lead chromate in a wax-emulsion medium relative to that of oil-based mediums. To better understand the behavior of lead chromate in wax-based mediums, a historical synthesis of lead chromate was recreated, and the pigment was suspended in four different binder matrices: a wax-water emulsion, refined linseed oil, cold-pressed linseed oil, and poppy oil. Each of these paint-binder mixtures wasaged beneath full-spectrum 6500 K LED lights. The relative darkening of the pigments was measured using UV-Vis reflectance colorimetry, and comparisons were made between the mediums.

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