Cochineal scale insects (Dactylopius coccus) grow on cacti in the Southwest. The infestation may be be all over the cactus plant as tiny white pulpy blobs. The insects produce carminic acid, which deters most other insect predators and produces a deep red color known as carmine.

Tree trunks aren’t always brown, nor are the bodies of ponds necessarily blue. This is one of the first hurdles that painting students, whatever their age, must get over as they begin to paint landscapes. Tree trunks and water both reflect light, as does everything else in our environment.

I climb up a cliff to examine a clump of dirt, slowly rubbing the silt between my fingers, feeling the texture—is it scratchy or chalky in texture? I get out my spade and collect a sample, depositing it into a plastic bag.