We have decided to colour the background of the icon now to be more aware of the harmony between the colours and to better control their intensity. The mixture is composed of Naples yellow (substitute) with a touch of yellow ochre (1/8). Add quite an important quantity of egg emulsion because the Naples yellow "eats" a lot of binder. The resulting mixture must be quite liquid, since we are going to apply it using the puddle technique.

Before applying the puddle on the background, make sure that the engraving of the inscription has been done.

After applying the puddle, a few marks can appear while it is drying. Don't worry, they will disappear once the layer is completely dry. Once it dries, go with one finger over the coloured surface. If the colour sticks to your finger, apply another layer of emulsion diluted in 30% of water to fix it well to the surface.

You can also use real Naples yellow to colour the background, but be very careful: this pigment is highly toxic!