Chemistry and Art
Laboratory: Pigments - Microscopy
In this is the lab you will work with several white and several blue pigments. You will work in groups of two - in groups of two! i.e., there will be groups of four divided into two groups (A and B). The idea is to get as much information about the pigments as you can. Along the way, you should share ideas and observations with your partner group which is testing some other pigments.
The Microscopy work will be with the microscopes that we used last week, the compound microscopes and the stereo microscopes. Top lighting is needed for some observations.
Arrange all work in large tables - stretching across a set of two facing pages.
Preliminary observations: Spend a maximum of 30 minutes on this part!
Groups A: lead white, gypsum, titanium white; cobalt blue, ultramarine, Prussian blue, azurite
Groups B: zinc white, chalk, titanium white; cobalt cerulean blue, smalte, indigo, azurite
Size - with these microscopes and lack of easy measurements, about the best you can do is some relative measurements - tiny, medium, etc.
Transparency (transparent or opaque with transmitted light). Appearance with reflected light (from above - use stereo microscope now)
Homogeneity and Association - what else is around?
Color (transmitted and reflected light)
Refractive index - need a mounted sample
Birefringence - really need a good microscope with rotating stage- but can get an idea with crossed polarized light using polarized plastic strips
Use the flowcharts from McCrone.