Cum bene temperatum

When saffron is thoroughly tempered, it often happens that, as it remains standing in the glair, it turns to a reddish colour, owing to an excess of the herb which is called saffron. Therefore you should seize the proper moment in tempering for painting; or else, as soon as the preparation is well tempered, remove the saffron from it, so that it may not tinge the tempering any more than is required.