May 9, 2009

Various recipes exist for gesso. Here’s what I use:

The Glue:
Dissolve 2 3/4 ounces of dry rabbit-skin glue with one quart water in a big glass jar (used pickle jars are great for this). This equates to 75 grams dry glue to approximately one liter of distilled water. The proportions work out to approximately 10/1 water to dried glue by volume. Many professional egg tempera painters suggest a higher percentage of 16/1. (I will try this next time around.)

Let it soak overnight.

Heat the glue in a double boiler, that is, with a second pan surrounding the jar with the glue water. The water should be the same temperature as the glue water, so bring the heat up slowly to melt the gelatine glue. Stir gently. The glue should never boil, only melt. Overheating significantly harms the adhesion of the glue, so do not let the temperature rise above 135 F° (57.3 °C), 127F° (53°C) is optimal.

The Filler:
I use calcium carbonate or precipitated chalk or whiting for filler with 10% titanium white or zinc white to insure a bright whiteness to your gesso.  The chalk whiting part can vary in both purity and whiteness, depending upon the grade. Industrial grade chalk whiting can be found in most hardware stores or paint shops but I currently buy my calcium carbonate from Kraemer Pigmente. Dry pigments can be found at art supply shops or online suppliers (like Kraemer).

The proportions are 1 lb filler (or 450 grams) to one quart (liter) of glue water.  Or 1 1/2 filler to 1 glue water by volume. The chalk is gently poured into the melted glue. I hold a funnel above the glue water, slowly adding the filler. Ideally you should be able to add all the filler in this way until a slight pyramid of filler forms above the fluid surface. Gently stir the mixture, but be careful to avoid creating any air bubbles. They can translate into pinholes in your gesso that are impossible to remove, adversely affecting your pristine starting ground. Lumps can be stirred or strained out (with cheesecloth).  The final result should be about the consistency of light cream.  Return the mixture to the double boiler (as necessary), keep it warm, but never let it remain too long on the heat as this can adversely affect the integrity of the RS glue.

Applying the Gesso:
Sand the panel lightly to remove any rough texture, clean the dust off with a moist cloth.  Cover the board with a light coating of size (1 1/2 oz rabbit skin glue dissolved in one quart water or 45 grams glue to one liter).  After the size has dried, begin applying thin coats of gesso.  The first coast is loosly brushed or scumbled in. I prefer to apply the gesso to both sides and ends of the panel to avoid any uneven absorption of moisture which might cause warping. I use a wide flat bristle brush (2″), applying thin layers in alternating horizontal and vertical layers.  The layers dry quickly, especially in warm weather.  Generally a well prepared panel can take about 10 thin coats of Gesso. I wait until 3 or 4 levels have accumulated and begin lightly sanding it down between layers, and then use a moist cloth to remove the dust. For proper adhesion between the layers of gesso it is best to complete your panel in one day’s working session.

After the final coat, the sanding moves from coarse to fine.  As a last step, it’s possible to take a slightly damp cloth and rub it gently over the entire surface in circular motions in order to obtain a final smooth, egg shell-like finish.  If, however, you intend to use the panel for silver point, it is best to leave that last step out in order to retain a slight tooth to the panel.

2 Responses to “Gesso”

  1. Nancy Says:

    Any experience dealing with lead-based gessoes (maybe house paint) from the Depression/WPA era. Eventually the lead does its chemical thing, creating soaps which then form bubbles which then pop the paint off the surface in tiny bits all over the painting. Most annoying! Any ideas how to stop the chemical process of the lead? Or infuse the primer which is fast becoming dust with an adhesive to re-bond the painting to the substrate? Prefer not to face the painting and give it a new canvas. Thanks! N

  2. Hi Nancy,
    Well, I do have some experience with using a lead gesso in an oil based primer, but it was many years ago (approximately 30 years ago). Nevertheless, the paintings created from that gesso are still alive, vibrant and very well. My substrate was seasoned hard wood. What is yours? Linen? Or cotton canvas? If you mention WPA, then it sounds to me as though you are involved with restoration. You probably need to be doing some precise chemical analysis to determine what is going on. Paint is always a marriage of pigment and binder on a substrate.

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