Monday, June 04, 2012

How to Make Your Own Gesso

I've become quite enamored with Gesso lately. I started using it on my Art Journal pages and discovered that it gives a much better surface for mixed media and keeps the paint from bleeding through the back side of the page. I like the Liquitex brand best, but it gets a bit expensive since I like to slather it on with a credit card pretty thickly.The best price I've found is on Amazon:

Meanwhile, I'm going to research and experiment with making my own gesso to try to save some money.

Historically, gesso was made by mixing calcium carbonate, gypsum, and/or chalk with glue. When applied to wood, it hardens to a bright white and can be used as both a primer and a material for sculpting (like the raising, decorative work on frames). In Renaissance times gesso was used as a ground for tempera paint. On furniture and decorative moldings it can be built up and carved into. Historically, gold leaf was applied to wood that had been coated with a layer of gesso.

Modern gesso follows the same principles, but adds acrylic polymer and chemicals to maintain flexibility.

Calcium Carbonate is a chemical compound (formula CaCO3) that is commonly found in rocks all over the world. It is the main component of seashells, snail shells, pearls and eggshells. It's the active ingredient in agricultural lime & is the primary cause of hard water (it's the hard white stuff that builds up on your bath fixtures). It's also what used in calcium supplements & as an antacid, but taking too much can be hazardous. Easier than grinding up rocks and shells, Plaster of Paris (the result of calcination of gypsum) can be used. Chalk can also be used, but the "real" kind, not the synthetic stuff you buy at a school supply store.

I've found that whatever gesso I use, it's really hard on brushes. I use a really cheap brush that I only use for gesso application, and don't expect it to last very long.

MAKING YOUR OWN GESSO:

There is lots of research on historical methods of making gesso. The product we buy today is a modern version of the original.

METHOD #1: (Plaster of Paris and Glue)


1. Slake your plaster of Paris by mixing together 1 part plaster of Paris and 4 parts water. Let the mixture sit until the plaster settles to the bottom. Then pour off the water and mix again. Repeat this process three times. The plaster reacts with the water. If the mixture gets warmer than when you started, repeat the process. If it appears to be the same temperature as when you started, then your plaster is slaked.


2. Scoop out the plaster of Paris and let it dry completely. Break up any clumps that appear (they may have pockets of moisture). Use a standard kitchen cheese grater and grind it into a fine powder.

3. Mix three parts of the slaked plaster of Paris to 1 part white glue. Add several drops of honey to every tablespoon or so of this mixture. Mix thoroughly and pound out any lumps. Your mixture should have the consistency of pancake batter. The gesso is now ready to use.

4. If you want to color your gesso, mix in a coloring agent. Watercolors, gouache oR acrylics all work well, are fairly inexpensive and easily acquired.

Store your gesso in an airtight container. Add a little water if the gesso becomes too dry. When applying gesso never put your brush directly into the storage container. Always pour out what you need and discard what you don't use. Gesso is easily contaminated and the whole jar can easily become a stinky, rotten mess.

Plaster of Paris is available at most art/craft shops or by mail from Amazon.


METHOD #2 (Dextrin Powder, Plaster and Glue)

1. Mix together 1 cup of dextrin powder (you can order online: DEXTRIN, YELLOW - 1 lb for about $4) and 1 tbsp. of hot (minimum 110 degrees F) water in a mixing bowl. (Yellow dextrin is a glue product, not to be confused with white dextrin which is a food additive that's used as a binder to hold things together. Then there's malto-dextrin which is yet another food additive. But it's yellow dextrin that you want for gesso.)


2. Add 1 tsp. of the dextrin solution and 1 tsp. of standard white craft glue in a separate mixing bowl and stir. Add 1 tbsp. of patching plaster and mix well.  This makes a fairly thick paste, suitable for making raised decorative shapes on frames etc. The paste should be pretty stiff but still viscous enough to pass through a 1/4-inch pastry tip. Scoop the gesso paste in a pastry bag fitted with a 1/4-inch diameter pastry tip. Apply the paste as needed and allow 2 hours for it to dry.

3. To use the gesso for priming canvas or paper for painting or mixed media work, add 1/4 cup of hot water and mix well

Store your gesso in an airtight container. Add a little water if the gesso becomes too dry. When applying gesso never put your brush directly into the storage container. Always pour out what you need and discard what you don't use. Gesso is easily contaminated and the whole jar can easily become a stinky, rotten mess.

METHOD # 3 Chalk & Glue

Follow Method # 1 instructions substituting chalk for the grated plaster. I'm lucky to have a rock-climber in the family, so I can dig into his Loose Chalk bag. It's pretty cheap, and easier to use than making plaster, drying it & grating it. Calcium Carbonate is technically what was used historically. It's a little more than $6 a pound.

METHOD #4 A Modern Adaptation of Cennino Cennini's Recipe
Tom Irizarry has written an interesting article on adapting ancient recipes to modern times can be found here. It also has a good bibliography for further study.

I'll continue to update with resources. Please add comments with your own research and relevant links.










4 comments:

Anonymous said...

What does the honey do? How did you figure this out? This would save me lots of money!

Anonymous said...

Where do you get your Dextrin Powder? How long does the gesso last?

Barbara Jean said...

wow. sounds like a lot of work, but I do know gesso is expensive if you use mush of it.

thanks
barb

Carlyn Clark said...

I get my Dextrin from Amazon. Click on the link and it will take you to what I buy. I don't know how long it will last. I put mine in a plastic bucket that drywall mud comes in and I've had it for almost a year & it's still fine. I keep a smaller container that I use when I'm working so the big container is never open very long.