After the scratch coat has dried,a second application of plaster is applied.This is an experiment with a tinted coat of plaster.Traditionally,white lime plaster is painted on directly while still wet,with a paint made of ground pigments and water.Distilled water and lime safe pigments must be used in fresco painting because chlorine from tap water will bleach the colors.Since lime is alkaline,it already reacts with the colors,typically only earth pigments are stable in lime,other pigments will bleach outAll colors tend to fade significantly while drying in reaction to the lime.A particular difficulty is working with blue,as ultramarine is not stable in lime.Cobalt blue is,but it is toxic and wearing a dust mask is particularly important.As such blue colors were traditionally painted after the fresco dried,with egg tempera,the same pigment and water with the addition of the binder of egg yolk.This color sat on top of the fresco and does not bind with the lime and therefore is not as permanent and may flake off.This experiment was to see if tinting the plaster directly,with a liquid cobalt pigment would help maintain a saturated blue color.