Which Pigments are the Best: Rate of Mould Growth on Tempera Paint
Katriona Pavlik
St John's School
Floor Location : J 229 D

Renaissance painters, such as Michelangelo, mixed tempera paint daily. I was interested to know why they did this and how using different pigments might affect the rate of mould growth. My hypothesis is if tempera paint is made using Bone Black pigment, which is composed of charred bone, mould will grow at a faster rate than on tempera paint made with synthetic pigments such as Ultramarine Blue, Titanium White, or soil pigments such as Burnt Sienna. I tested four pigments Ultramarine Blue, Bone Black, Burnt Sienna, and Titanium White, by combining the pigments with egg yolks and water to create tempera paint. I placed all the test samples in the same covered container and I observed that mould grew at a faster rate on the tempera paint which was made with Ultramarine Blue pigment. The Ultramarine Blue pigment is a synthetic version of the stone lapis lazuli. The mould grew the slowest rate when the tempera paint was made with Burnt Sienna pigment which is soil mined in Sienna Italy. The paint with Bone Black pigment did not grow mould as fast as the Ultramarine Blue but did grow mould faster than the Burnt Sienna. I also observed that more mould grew on the samples placed slightly farther away from a window which was a source of heat and cold. The type of paint pigments made a difference in the rate of mould growth. The location of the paint also effected the rate of mould growth. The tempera paint made with synthetic pigments grew mould faster than the paint composed of soil pigments. Mould growth in tempera paint can be slowed by the type of pigment used and the location in which the paint is stored.