The support one chooses for a tempera painting is the first critical element in the painting process. Tempera paint requires a slightly absorbent ground because of the relatively weak binding strength of the egg.
Traditionally, a true chalk gesso ground is used and as this substanc is relatively inflexible it requires a rigid support like wood. Historically, slowly cured straight grained soft wood like poplar or basswood was used a a support.
Wood in itself has some shortcomings like warping, splitting and the raising of the grain. Gesso does little to prevent the damage to wood brought on by moisture and atmospheric changes.
Wood may also emit acidic gasses and it is recommended that the wood be primed with a glue and calcium carbonate ground to insulate the paint layer from acidic vapors.
A thin layer of linen may also be applied before the application of gesso to lessen the tendency of cracking.
Works on wooden panels should be kept relatively small, 18″ on their longest dimension. The wood should be free of knots and irregularities and should not be hard or resinous.
Though stable against warping and splitting, this material has a surface grain which is subject to raising which may cause fine cracking throughout the gesso. Many plywood panels are made from pine or fir which contain resin that prevents the gesso from adhering properly but those made from birch plywood are more suitable.
Like all wood panels, plywood panels absorb and give moisture with resulting expansion and contraction. The movement occurs in every direction with plywood and there are numerous examples of paintings on plywood and virtually everyone of them have eventually cracked. Early egg tempera painters reduced this risk by embedding a layer of thin fabric in their gesso ground and it does work. If you are using plywood or wood panels, apply an old well washed bed sheet to the panel first either with glue size or embedded in the first layer of glue gesso.
Inferior grades of plywood have the laminates glued together so poorly that over time may separate.
Wood Pulp Boards
Hardboard (Masonite) and Medium Density Fibreboard (MDF) make the most suitable and inexpensive supports, although their longevity has not yet been established.
The board can be formed in one of three ways, The Wet Process and Wet/Dry Process involves the reconstitution of the lignin to bond the wood fibres. The Dry Process has little of the lignin present so phenolic resins are added to bind the fibres.
Hardboard is known to have a sever outgassing problem but using a glue gesso ground containing calcium carbonate will insulate the paint layer from the acidic gasses.
Tempered masonite is more durable than untempered, that’s what the process is for. Tempering involves impregnating the board with oils to make it water resistant and more resistant to wear. The problem is that coatings, especially aqueous coatings such as gesso, are likely to bond poorly with this oil impregnated surface, and as with many of the problems that are likely to arise with paintings that are (hopefully) expected to last a long time, this defect may not arise for a good many years. A painting that is only a few years old has not been around long enough to judge the suitability of using tempered masonite as a support. The latest edition of “The Artist’s Handbook” suggests that most conservators now consider masonite a poor support for painting. One wonders if this is simply because they are seeing mostly the damaged panels that are in need of repair, or if we, who faithfully use masonite, are all in trouble. I can imagine that there are a good many paintings done on masonite that have been banged around the studio and rolled in and out of the closet that are in poor shape, but how many of us here have paintings on masonite that are even slightly chipped? I believe that, if properly gessoed and properly cradled, untempered masonite is a perfect support.
(Richard Thomas Davis)
Hardboard and medium density fibreboard can be purchased in a variety of widths. Quarter inch thick panels are less likely to warp and cause the gesso to crack. Large panels (over 36″) should be cradled. This is achieved by fixing battens of timber along the edges and at suitable intervals within that framework.
This has the same stability as wood pulp boards but are thick and heavy and are only suitable for small works. A high density particle board is also available however the chemical binder used may be incompatable with gesso and the paint.
An acid free, heavy weight paper may be used for tempera painting.
Because paper is flexible it is not a suitable support for chalk gesso.
If paper is to be the chosen support it is recommended that a heavy water color paper is used or better still, watercolor board which is rigid card with watercolor paper bonded to it. The paper does not need to be sized or have a ground applied. A number of thin coats of tempera will have to be applied to reduce the absorbency of the paper before ‘proper’ work can commence. Canvas
This is rarely used as a support because it is too flexible and any movement will most likely cause the gesso to crack.
Some earlier paintings were painted on canvas but have not stood the test of time as those painted on panels.
Interglow panels are described by the manufacturer as having been constructed of three layers of Douglas fir faced on both sides with mahogany sheets. The outer sheets of mahogany are sanded and layered with acid-free craft paper saturated with 28% fenolic thermosetting resin. The panel is heat set and primed with acrylic.
Acrylic primer is considered not compatable with egg tempera.
It is believed that clayboard is also primed with acrylic. An artist who tried this product found that the paint tended to lift off. The manufacturers state that this product is not suitable for egg tempera.