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Glue/Chalk Emulsion Ground problems

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I’m student at an academy of fine arts in Europe. I used to paint on Wood and primed with acrylic gesso from Golden. I recently made the change to canvas and home made ground and that’s where the nightmare began. The priming recipe for oil painting on canvas given by my teacher consists of Rabbit Skin glue, Champagne Chalk (with optional titanium white) and Lindseed oil varnish. I made the first 5 with him and got excellent results but since I have had to make them by myself, I lost a month of painting and so much material because all my primed canvas cracked, I cannot understand why…
1) I mix 55g of RSG with1L of water overnight in the fridge2)Take one part of that with 2.5 Part of water and do one layer of sizing3) Take on part with 2 part Champagne Chalk with 1 Part water with 1/3 Lindseed oil varnish and use an electric mixer. Then I apply 3-4 coats
The next day I arrive and everything show mini cracks. I can hear them if I press gentle on the back of the canvas
I have asked 50 times my teacher and I swear I’m doing what I think he tells me, but obviously something I do is wrong… Do you have any idea what the problem is? do you recommend another method specifically
I use cotton duck canvas which I stretch. It is for oil painting. I like firm tension but that can take some rough cloth rubbing and handling. Longevity and quality are very important to me.

I’m not experienced with oil-based gesso, but I’ve been making traditional chalk and glue gesso for decades – and for that it is important (as I am guessing it is for an oil-based gesso as well) to consider the glue. Ideally, the glue should be 100% collagen, which is generally the most elastic and strong.  Once hydrated, a glue should be refrigerated and, even when refrigerated, should be used within a few days up to a week or so (being an organic substance, if a hydrated glue sits out for too long it starts to break down).  Finally, in my experience it’s very important not to overheat the glue. If glue (or gesso) gets hotter than about 65 c., or 150 f. the heat will break down the glue proteins.  Always work with a double boiler; always first heat the water in the double boiler without the glue in it, than take the double boiler off the burner before adding your glue (in other words, never have either your glue or gesso directly atop a heat source, even in a double boiler bath).  A good glue doesn’t need much heat to dissolve.  I never allow my gesso to get warmer than I can comfortably dip my finger into (about warm tap water).  If a glue is compromised in any of the ways above, it can (in my experience) potentially cause cracking.
The other primary reason a traditional chalk and glue gesso cracks is if the ratio of glue is too high.  The ratio has some variability: for example, I prefer 1 part glue to 16 parts water (then I combine 1 part of this glue water mix with 1.5 parts chalk). Other people prefer slightly stronger or weaker glue formulations, but at some point, if the ratio gets any too strong – above about 1 part glue to 12 parts water – this creates too strong a gesso, it pulls apart and cracks.   However I’m talking about a pure chalk and glue ground, not an oil ground, so these ratios probably aren’t relative (since oil imparts more flexibility).  I don’t mean to comment on the precise recipe you gave,  I only mean to say that whatever recipe you follow, be aware that too much glue at some point can also cause cracking. 

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​Very interesting problem….first I would have to state that it is not advisable to use glue/oil/chalk emulsion grounds on flexible supports simply due to the fact that they tend to be too brittle and therefore are prone to developing cracks (a problem that you are already encountering). I am also not sure what “Linseed oil varnish” is….could you perhaps clarify? Does this oil contain a natural resin like dammar or mastic? If so that would certainly make the emulsion ground even more brittle (natural resins are not recommended for use in ground/priming layers due to their inherent brittleness). If you do choose to continue experimenting with these types of grounds on canvas you might look up some recipes that can be found in Kurt Wehlte’s book or Max Deorner’s text (both references are listed in the downloadable pdf called “Artists’ Manuals” that can be found in our Resources section). I myself played around with a recipe from Deorner’s text that applied to a reconstruction of a painting by Arthur Dove (again this can be found in our Resources section) on canvas:
Max Doerner’s “Half chalk Ground” or “Tempera Ground”:

“An equal measure of chalk and an equal measure of zinc white are combined with an equal measure of the glue-water mixture (same proportions as used for the sizing layer, 70g:1 liter).  All three components are thoroughly mixed to which 1/3 amount of boiled linseed oil is added.  After this has dried, apply further coats.”

Mind you zinc white is now known to cause potential problems when mixed with drying oils (can cause chalking, brittleness, delamination, etc.) so you might use titanium white instead and/or up the amount of chalk. If you do decide to continue using glue/oil emulsion grounds on canvas please consider possibly mounting your canvas to a rigid support and recording your materials on the reverse of the painting. Both will help promote the longevity of your work!

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