"For the use and good and profit of anyone who wants to enter this profession."
-- Cennino Cennini, sometime before 1437
Priming the Panel
You will need:
- Your rabbitskin glue-sized panel (See "Sizing the Panel")
- Your prepared chalk gesso (See "Making Chalk Gesso" )
- A double boiler or saucepan of water
- A priming brush
- Sandpaper, medium fine and very fine
- A dust mask or respirator
This process takes a few days, although you do less than an hour's work each day. I recommend priming several panels at a time for maximum efficiency.
1. Place the jar of gesso in a pan of COLD water and slowly warm them together. (If you have freshly-made your gesso, as instructed here, leave it in its bath of hot water)
2. When the gesso is warm and soft, stir it gently. You don't want bubbles. It doesn't need to be warmer than the minimum necessary to keep it at a creamy texture. At any rate, try not to let the gesso get hotter than 127 degrees fahrenheit (52 degrees celsius).
3. Dip the priming brush into the warm gesso, brush excess back into the jar, and lay a smooth coat on the panel, the brushstrokes all going one way. Prime the edges of the panel too. You may need to add a little water to the gesso jar now and then, as it evaporates; you want a thin texture. But don't overdo it.
4. Allow the gesso to dry. For the first coat this may take less than a hour, but subsequent coats will take longer and longer.
5. Alternate priming one side and the other of the panel and direction of the brushstrokes -- lengthwise, widthwise, diagonally this way and that.
6. At some point you must sand the gesso. Some like to sand it mirror-smooth after every layer, others don't sand until all the gesso is on. I like to sand after the first two or three coats, then after every other coat until the panel is done. The considerations are these:
The panel must be utterly dry before you sand -- at least an entire day's drying.
All the brushstroke ridges must be sanded down (This is why you don't want a very thick gesso.). Use the medium sandpaper first, then polish with the fine. Optionally, you can give a final polish with a piece of undyed linen wetted and wrung out until just damp -- it's fussy work, but gives an almost mirror-shine to the gesso.
You will end up doing the same amount of sanding no matter what. You can do it spread out over days or in one big marathon at the end.
Once sanded smooth your gessoed panel is ready for painting.
Remember to wear a dust mask or better, a NIOSH-approved respirator when sanding
Do not handle the gessoed panel with your bare hands. Skin oils will mar the painting surface.
If your masonite has a rough back, or you are sure you will not paint on the back of the panel, you need only put two or three rough coats of gesso on, and you don't have to sand it smooth.
Letting the gessoed panels dry for extra time improves them. This is another good reason to gesso several panels at once.
The next step is to make the egg medium.