e norm for plein air painters. Studio painters may 
work alla prima, but at least as many prefer to working in layers. This means 
painting one layer and letting it dry before working the next. While one can 
approach this as simply alla prima painting that has been slowed down, and with 
less worry about layers muddying each other, the traditional reason for working 
in layers is to use the technique of <i>glazing</i>. This involves building up 
colors through layers of transparent paint. For example