When well prepared, these pigments are remarkably solid, and have changed but little during the lapse of ages.

The reds have darkened, the greens have faded, the blues have turned somewhat green or grey; but this is only on the surface.

If that surface is scraped off, the colour underneath is brilliant and unchanged.

Before the Theban period, no precautions were taken to protect the painter's work from the action of air and light.

About the time of the Twentieth Dynasty, however, it became customary to coat painted surfaces with a transparent varnish which was soluble in water, and which was probably made from the gum of some kind of acacia.