This is a small painting (36 x 26cm). The painting time was a little over one hour. I have more information in previous post. There are 2 blues used in this painting, Prussian and Cerulean. They are very different from each other. Prussian looks almost black in colour when placed on the palette. Its has enormous tinting power and is transparent. Its richness of colour is seen when spread on a white surface then the white reflects through the paint layer. When mixed with Titanium White, which is partially transparent, the resultant colour has a rich glow.
However, this does look a little unnatural in landscape paintings and this is where Cerulean Blue comes in. This blue is light in colour when placed on the palette. Its non-transparent and has weak tinting. When mixed with even a little Titanium White it looses it blue tint and becomes a ‘smokey’ greyish blue. This combined with Prussian can produce a variety of blue colours. As you will see in the video, I made up a mix of Cerulean and white which is used to sketch out the cloud shapes and spread upwards to the top of the sky. The pure Prussian is placed into this mix, more at the top to produce the deepest colour blue.
The cloud shadows are a mix of Prussian Blue, Indian Red, Raw Umber and a little black to lower the tone. The variety of blue shades is produced when the sky is ‘blended’ with the large brush. There is very little medium (Liquin) used at this stage as this would cause the entire sky to mix into one homogenous colour and not only the blue shades but also the cloud shapes would disappear. It is important to have the 2 blues present from top to bottom of the sky to avoid an unnatural 2 colour banded sky. The 2 blues enhance each other producing a cold clear blue above our heads to the misty colours at the horizon. The 2 blues were also used in the painting of the ground, especially the darker ‘greenish’ shadows, to tie the sky and ground in the interests of harmony of colours.
Here’s the video.