MITRA Forum Question Details

​​Hi Roger,

Having made animal glue grounds for 30 years, one would think I might have tried freezing it - but I haven't.  For me, animal glue is inexpensive and readily available - I make what I need of glue and gesso; if any small amount remains I toss it in the woods (animal glue and chalk being harmless to the environment).  A high quality glue - not old or rotten, strong (minimum bloom value of 400) - is critical to good quality gesso.  So I always start with a fresh batch of glue, made from rabbit skins & 450 bloom strength.  However, in perusing the scientific literature on the subject, the consensus seems to be that it's fine to freeze animal glue after it's been hydrated.  I couldn't find anything about freezing gesso - give it a try and let us know how it behaves.   I hope you enjoy your foray into egg tempera - it's a wonderful medium.  

Koo Schadler

Hi Roger,

A gesso recipe based on ratios versus specific measurements allows you to customize how much gesso you make.  So, for example, my ratios are...

- 1 part animal glue to 16 parts water (which yields 16 parts glue water)

- 1 part glue water to 1.5 parts inert, white, solid particles (i.e. chalk, gypsum).

You can measure out the above ratios in ounces, grams, use a thimble, whatever.

I generally measure with ounces. Hence I end up with 16 ounces (2 cups) glue water, to which I add 3 cups chalk (2 cups glue water x 1.5 parts solids = 3 cups).   This is enough gesso to coat one side of a 2' x 2' panel with approximately  8-10 coats.  

But if you wanted to make a smaller batch of gesso, you could choose a different measurement, such as:

-  .25 ounces glue + 4 ounces animal glue (= 4 ounces glue water)

-  4 ounces glue water + 6 ounces inert solid particles

This would yield, obviously, 1/4 the amount of gesso relative to what I make. 

Granted, when you get into very small amounts of gesso, it tends to dehydrate and thicken more quickly  so it's best to use an appropriately small sized container (that sits in a warm water bath) and check it often to make sure it's staying nicely hydrated. 

A few notes on the above:

1.  The 1 part glue to 16 parts water does not yield 17 parts glue water because the glue so fully absorbs the water.  Hence the final glue water amount of 16 parts.

2.  These ratios can be tweaked a bit. Some people prefer a slightly harder, stronger gesso and use a bit more glue; some people prefer a softer, more absorbent gesso and use a bit less glue.  So while I find a 1:16 ratio perfect for the type of gesso I like, you may opt for different ratios.  

Hope that give more options with your gesso making.   

Koo​

​Hi Roger,

A few more thoughts, which you may already be aware of, but which are important considerations and worth a mention.

Gesso should not be thick - not like dense cream, it should be more like light cream or even whole milk.  It's better to apply multiple thin layers than thick layers.

On a very humid day (i.e. a rainy day) a layer of gesso can take up to an hour to dry.  Under dry conditions (i.e. a heated or air conditioned room, or low relative humidity) a layer can dry in 10 minutes.  So drying time of layers varies greatly depending on atmospheric conditions.  Also, the more layers you accumulate, the more time they take to reach touch dry (when you gently put your fingers on it, you don't disturb or lift the gesso)​. 

A layer should be just touch dry before you apply the next layer.  The next layer should in no way lift the underlying layers.  

A matte finish is inevitable with any high PVC (pigment volume concentrate) ground or paint, because the ratio of solid particles (gypsum or chalk in the case of gesso) is so high, pigment particles rise above the surface of the binder (animal glue) and create a microscopically rough, irregular surface that scatters light (see image: Screen Shot 2021-10-14 at 8.46.32 AM.png).  So a matte finish isn't dependent on how one applies gesso, but merely an inevitable consequence of gesso itself.

It's great that you're making your own gesso - it's wonderful to acquire that craftsmanship, and it is the most receptive, best surface for egg tempera.  Enjoy!

Koo