Preparing Glue Size (Rabbit Skin Glue) DAY ONE AND TWO
- Soak one measure (by volume) of glue to 12 measures of cold water
- I used 1/4 cup RSG to 3 cups water in a big tupperware container I do not plan to use for food again
- Allow glue to soak preferably overnight
- The next day it is a gelatenous substance.
- Heat glue mixture in a double boiler bath - I don't have a double boiler, so I just nested two pots together which worked fine: I boiled a half-pot of water on a portable electric burner in my studio, and nested a smaller pot inside. The smaller pot is non-stick. The glue melts and becomes liquid very easily.
- Apply glue while warm with a flat brush - I used a housepainting brush, but a softer art brush is probably better.
- Be warned: this is makes sticky mess, since you need to cover the panel on all sides and there is nowhere to hold onto it. I discovered this method works best:
- Hold the panel from underneath on your fingertips, like a waiter holding a tray, and then brush the glue onto the (top) painting surface and edges.
- Lean the panel against a wall, so just the top edge or corner is touching, and them gently brush glue on the back side. (I scored and folded foamcore to protect my wall and floor)
- Usually two layers are enough to seal the wood effectively. It dries fast, in about an hour or less I could do the second coat. Then I let the panels dry overnight.
- At this point it is advisable to adhere a piece of fabric (thin muslin sheeting) to the panel to help stabilize the ground and to protect it from joints in the panel that might show in the gesso. (I did not do this - I like my painting surface to be very smooth and I didn't want the cloth texture.)
- The left over glue-size then gets used for the chalk ground.
- NOTE: The RSG turns to jelly again if you let it cool, it firms up quite a bit of you leave it to cool overnight, but you can re-heat the next day, it works fine.
Chalk Grounds: Ingredients DAY THREE, FOUR, FIVE....
3 parts of glue size (by volume) (I made extra RSG and used 3 cups)
1 part chalk (I used 1 cup)
1 part pigment (white, english red, umber, etc.)
I found it needs more pigment, otherwise the gesso is too watery and transparent. I ended up using more than 1.5 parts.
I used Titanium because I did not want to deal with the health hazards of sanding the lead-based "Flake" white
Chalk Grounds: Directions
- Measure out the glue size solution into a metal container (I did not understand this at first - but it is to help measure correctly, since it is hard to know how much is left over in the double boiler once you have used it to coat the panels. I used a large metal mixing bowl.)
- Add the dry ingredients
- Stir well but do not whisk to prevent air-bubbles (I used a wooden spoon, worked great)
- Place container in a double-boiler bath (see my nested pot solution above)
- Apply warm mixture with a broad brush (I found it's better if the gesso is only slightly warms - when the water in the bottom pot is not full boiling, just simmering. The gesso is a bit thicker and covers more when it is only slightly warm, not hot.)
- Allow layer to dry to the touch and recoat. (I found it did not dry fast enough to re-coat within a few hours. I ended up letting it dry overnight between each layer. I also sanded between before each subsequent coat with a small handheld power sander I bought for less than $40 - so worth it!!)
- Note: When applying layers of ground, brushstrokes should be applied in one direction for every coat. Reapply subsequent layers in a perpendicular direction to the previous application. Yes this is true - otherwise deep grooves can develop which are hard to sand away.
- I ended up doing 3 coats of gesso on most panels, and 4 on a few of them. It ended up being a week-long project, spending about an hour per day.
- The gesso cools in the pot and gets quite firm overnight. I just left it in the double-boiler and re-heated the next day, it turned back into brushable paint very quickly and the texture was fine. Sometimes I added more pigment or RSG as it warmed, depending on whether it seemed too thick or too watery.