Part 1: Prepare the Panel
The first step in the creation of an egg tempera panel is to prepare the panel's ground layer. Coating the wood with gesso is a time-consuming process, but critical to assure that the pigments and gold leaf will adhere and last without cracking.
|1||Cut the wood to size|
While soft woods such as birch and poplar can be used as the carrier, it's more convenient today to use untempered hardboard, one-quarter inch thick. In many ways, hardboard works better than wood as it is very flat, will not warp or crack, has no grain and is not affected by moisture. Sold in large sheets, hardboard must first be marked and cut to the desired shape and size. Panels can also be constructed from multiple pieces of board, hinged together into traditional religious diptychs and triptychs.
Working on smaller panels is best for the beginner, since the process is very detailed. Also, it is difficult to cover large areas with the tiny brushstrokes used in tempera, as the paint does not blend, but must be carefully layered.
Those who prefer to use wood must support it by constructing a cradle, in which wooden strips attach to the back of the panel to keep it from warping due to changes in temperature.
|2||Rough up the wood surface|
There are two sides to the hardboard, and we're going to paint on the smooth side. However, as both sides of the board will be gessoed,
(rollover to enlarge) we must first rough up both back and front to create a tooth. This will ensure a firm and even bond between the support and the gesso.
Roughing is done with a rasp or piece of coarse sandpaper, which is drawn, in several quick strokes, across the board's surface. We don't want to sand the surface, but to simply rough it up.
After rasping, be sure to wipe the board with a clean cloth to remove any dust before moving on to the next step.
|3||Prepare and apply sizing to the wood|
Sizing is a binder applied to the roughed-up panel to provide a coarse surface for adhering the gesso. Traditionally, sizing was made from various animal skins, but today it is quicker and produces similar results to use unflavored, powdered gelatin.
(rollover to enlarge)
To prepare the sizing, boil water in the bottom section of a double boiler. In the top section, measure the gelatin into cold water in the proportion of ¼ ounce of gelatin to 4 ounces of water (¼ ounce of gelatin will produce enough hot sizing to cover three 6-inch square panels).
Allow the gelatin to absorb all the water, and then place the pan containing the mixture onto the double boiler. Stir the gelatin until it's thoroughly dissolved and hot to the touch. Lowering the heat, but always keeping the gelatin hot, use a 2-inch brush to apply the sizing to one side of each panel. Rub the sizing onto the panel in quick even strokes (in one direction only), making sure to also cover the edges of the board. Then set each panel aside to dry. Remove the gelatin from the heat and cover it.
Once the top of each board is thoroughly dried, reheat the gelatin and apply it to the reverse side of each board. Before moving to the next step, allow the sized boards to dry for a couple of days.
|4||Prepare the gesso|
Gesso, a mixture of gelatin and whiting (calcium carbonate), is the ground onto which the gold leaf and pigment will be applied. Preparing smooth, even gesso is important as it provides a surface for these materials to strongly adhere to the board. The pure-white gesso also allows the layered glazes to achieve their characteristic luminosity.
(rollover to enlarge) To prepare the gesso, boil water in the bottom section of a double boiler. Meanwhile, in the top section, mix ½ ounce of gelatin with one cup of cold water. Once the gelatin has absorbed the water, place the pan over the boiling water and stir until the gelatin is dissolved and hot to the touch. Then turn down the heat under the double boiler, allowing the water to keep the mixture hot.
Begin sifting the whiting into the gelatin mixture. Do not stir, simply let the whiting sink in and absorb into the hot sizing (stirring will create bubbles that cannot be removed). Sift slowly to allow the whiting to absorb into the sizing gradually, which also will help avoid the fomation of bubbles. Use approximately 1¼ ouces of whiting (by weight) for each liquid ounce of sizing. The goal is to end up with a creamy, smooth gesso mixture — some experimentation with your particular materials may be needed to judge the best proportions.
As the mound of gesso grows, it may be necessary to gently move the unabsorbed whiting with a spoon into the liquid around the edges of the pan. Work quickly, as the gesso should not be allowed to cool.
When all the whiting is absorbed into the liquid, using a brush, VERY GENTLY fold the mixture in the pan together two or three times. Again, any stirring will introduce bubbles.
|5||Pour the gesso|
Next, the gesso is strained to remove any bits of undissolved whiting.
(rollover to enlarge) We do this by pouring the gesso mixture through a double layer of cheesecloth. The easiest way to accomplish this is to have a helper hold the cheesecloth over a container that will fit into the double boiler (so the gesso can be reheated as it's being applied).
Be careful to pour the gesso slowly so as not to introduce air bubbles. You may very gently coax it through the cloth using your brush. Once poured, do not stir. By this time, the gesso may have cooled and solidified a bit, so the container should be placed back onto the double boiler momentarily to restore the gesso to a liquid consistency.
The gesso is now ready to use.
|6||Coat the panel with gesso|
We now begin to apply several coats of gesso to the prepared board. The goal is to build up a thickness of gesso which is as smooth and even as possible.
Using a two-inch brush,
(rollover to enlarge) apply the first coat of gesso onto the glue surface in several slightly overlapping strokes, in a top-to-bottom direction. A primary concern of this first layer is to avoid air bubbles in the gesso, so make sure to dip the brush gently into the gesso, and, using a somewhat firmer stroke, rub out any bubbles on the panel as they appear.
Unlike the size coat, which had to dry thoroughly, successive gesso coats must follow each other quickly so the coats bind properly. The proper moment for each succeeding coat is when the previous coat has dried only slightly so the surface shininess has dulled. As soon as this sheen disappears, apply the next coat, brushing on the gesso using a crosswise stroke (in a side-to-side direction).
Alternate layers of gesso in this manner until you've built up seven coats. As you add more layers, it will take a bit longer for the shininess to disappear between coats. Though it's best to work with the gesso as cool as possible, if at any time it seems to be setting up, place the container back over the hot water for several seconds to liquify the gesso. The entire process will take about an hour, and the panel must be completed in one sitting to assure that the gesso layers properly bind.
The panel must then be set aside to dry thoroughly, out of direct sunlight, for about a week.
|7||Waterblock the panel|
After several days of drying, the panel is ready for waterblocking, which will smooth the gesso and create a silky surface
(rollover to enlarge) that is perfectly even in color and texture, which aids both in gilding and painting.
For this process, we use a two-by-two inch block of hardwood, sanded carefully on all sides. The bottom of the block is dipped into a shallow pan of water, and then the block is rubbed in a circular motion over the entire surface of the panel. A thin paste of gesso will work up and be redistributed, creating a smooth, even surface.
Continue working the block over the panel, constantly moving the block around and around. It's also important not to wet the block too much, which can soak the gesso, or to work on one small section too vigorously. These actions can soften the gesso and possibly lead to cracking. Only a small amount of water is used on the block so that only the top surface of the gesso is dampened.
Once waterblocking is complete, let the panel dry thoroughly. Then, using a piece of fine sandpaper wrapped around the hardwood block, sand a 45-degree bevel all around the panel's edge. As you sand, be careful to stroke the block in a downward direction only, to prevent chipping of the gesso.
It's also possible to create a raised design within the ground, either as a decorative border or to incorporate into the picture. This technique involves
(rollover to enlarge) building up sufficient layers of the warm gesso mixture along an outline drawn onto the panel.
Once the waterblocked panel has dried, create a lightly pencilled outline directly onto the smooth gesso. Prepare a quantity of warm liquid gesso (as above), though of a slightly thinner consistency than used in coating the panel. Using a small brush, apply the gesso in a thin layer within the outline. As before, allow the gesso to dry to a dull finish before adding each additional layer until the approximate shape is achieved. We're basically building up gesso to the required thickness — once dry, the built-up areas can be rounded, squared-off or otherwise shaped.
The gesso has a tendency to shrink slightly as it dries, so consider building up the shape a bit higher to allow for this.
Careful sanding with very fine sandpaper is now required to create the final desired shape on the panel surface. To work the corners and small areas, the sandpaper may be rolled around a brush handle. The gesso should be sanded smooth; special 'Wet and Dry' sandpaper can be useful in accomplishing this. The final raised pattern can then be painted — or gilded and tooled — if desired, as described in the following sections.