Here is a little portrait Ingres made. A grey surface he used to paint on, as you can clearly see in how the dark clothing is painted on the surface. The shadows in the face are darker than the gray ground, lighted areas appear lighter on the gray surface, just like in the drawing.

Here is a picture of the original. Because you painted on a white surface the colours are less solid. it's more logical to build up an image like this on a coloured surface.
the colour of the canvas was something like you can still see in the background on the right, a warm-brown colour. When you compare her face to the other face
painted by Ingres which I showed before you will notice a difference in warmth of the colours of the face. The coloured ground has a great effect on the overall-tone
and the appearance of the colours of the painting.

Hope this helps,
Peter

Thanks
 

Hello, Peter. Thank you for posting the painting technique of Ingres. Did you research this information from some of his book collections?