Pigment Synthesis for the Exploration of Binding Media Using a Lead-Free Alternative to Chrome Yellow

Abstract

Generating enthusiasm among nonscience majors in a laboratory course is a difficult task. Often, students are asked to perform a precipitation reaction, only to collect and then safely dispose of the solid without detailing composition, properties, or uses. In an effort to keep the students engaged, this laboratory exercise presents an innovative way to use the product of a precipitation reaction. The reaction chosen produces basic zinc(II) chromate, a yellow pigment that can be combined with various paint binders such as beeswax, gum Arabic, egg yolk, linseed oil, and acrylic medium. The students then test their paints on a canvas and analyze their different physical properties. This exercise can be tailored to match different undergraduate levels, ranging from nonscience majors to chemistry majors and be used as a part of a STEAM (science, technology, engineering, arts, and mathematics) activity. A brief discussion on historical paint binders and their chemistry is also included.