Virgil recommends tinting the ground to a Value 7 on the Munsell value scale (70% light). “I recommend not going any darker than that in toning a ground, because any darker a ground than that will cause the colors applied over it to grow darker as the painting acquires more age.”
Some Facebook users asked for advice on how best to draw their composition on their support before painting.
Graphite isn’t the best material to have under oil paints. I have seen graphite line drawings and grids showing through thinly painted oil paintings that were not yet old enough for it to be the kind of pentimento that is sometimes seen on old oil paintings whose paint has become more transparent with age. I surmise that it was just due to the paint not being opaque enough to hide it completely.
Graphite should not be used for an underdrawing for two reasons. Very dark lines may eventually show through increasingly transparent paint over time (the effect is called pentimenti). And a dark, fully resolved drawing with graphite may impact adhesion between the oil paints that follow and the ground.
Charcoal can be sharpened to as fine a point as graphite pencils and can then be used in the same way, with the added benefit of being easier to erase cleanly for corrections and adjustments.
The use of fixative introduces potential interference with adhesion of oil paint to the ground or underpainting layers, and to use hair spray is probably even worse an idea from a standpoint of longevity.
Underpainting is the stage in traditional oil painting whereby the artist applies a monochrome or dead colour layer as the base.
To be developed soon.
Lead White for Underpainting
With Rublev Lead White #1 as the main ingredient in my underpaintings, it’s dry enough to paint over in two days or less, and a better bond is created between layers because the underpainting and the paint going over it are chemically compatible with one another.
Consider also that the presence of lead white (without zinc oxide in it) adds physical strength and durability to all the oil paints in the picture, and helps them all dry better and cure better. No other white oil paint does this, and neither do acrylics. This means that an underpainting whose principal ingredient is lead white bound with linseed oil is structurally superior to any other underpainting material.
Rublev Lead White #1 begins to set in a few hours, and is usually dry enough to paint over in two days or less, so if the reason to consider underpainting in acrylic is eagerness to proceed as soon as possible, that objective is served well by choosing to underpaint in oils using the lead white I have just mentioned.
Acrylics for Underpainting
A Facebook user asks about the wisdom of some artists using acrylics for their underpainting.
I don’t see any good reason to underpaint in acrylics. Haste is usually the reason, but if oil paint is applied while there is still water in the acrylic underpainting, there could very well be problems from it. And if one waits a few days for the water to escape before applying oil paints, the advantage of underpainting in acrylics is not there, because the underpainting could just as well be in oils or alkyds then.
Rublev Lead White #1 begins to set in a few hours, and is usually dry enough to paint over in two days or less, so if the reason to consider underpainting in acrylic is eagerness to proceed as soon as possible, that objective is served well by choosing to underpaint in oils using the lead white I have just mentioned. Acrylics, for the best performance, should NOT be painted over with oil paints any sooner than that, because there would be the possibility of water still being in them.
There are water-soluble ingredients in acrylic paints that migrate to the surface with the water as the paint dries, and can then form deposits on the surface, which should be then cleaned off for optimum mechanical adhesion, according to Ross Merrill when he was Chief of Conservation at the National Gallery of Art in Washington DC. In the time it would take for this, or less, an oil paint underpainting with Rublev Lead White #1 as its main ingredient would be ready to paint over, so the perceived advantage of underpainting in acrylic paints is not well considered. To paint with oils over acrylic paints that are not cured well enough is potentially problematic. When we do things less than optimally well, we can’t and shouldn’t expect optimal results.
Other Technical Notes
Acrylic paints are not the same as acrylic grounds. The latter have ingredients in them that improve mechanical adhesion for subsequent layers. However, I do recall that Golden offers a special kind of acrylic paints that are formulated for use as underpainting material, which would be the exception. In their case, what I said about acrylic grounds would apply to them as well. Golden makes good quality acrylic products.
Artist Ron Francis also notes: “The problem with that technique [using acrylics for an underpainting] is the lack of adhesion. Acrylic grounds contain chalk which allows them to absorb some of the oil thereby enhancing the mechanical adhesion of the paint. But this isn’t the case with normal acrylic paint.”
To be developed in the near future.