Question asked 2019-12-27 09:21:36 ...
Most recent comment 2019-12-28 13:03:39
Grounds / Priming
In making gesso, my experience is to first establish a ratio of glue to water, my preference being 1 pt. glue to 16 pts. water (1:16). While I've always believed there is some variability in that ratio (my guesstimate, from 1:12 to 1:20), a past MITRA question clarified that, given the complexity of glue, the variability can be greater than that (i.e. one paint company recommends a 1:5 ratio) - it all depends on glue factors.
Anyhow, the second relevant gesso ratio is glue water to chalk or gypsum (whiting). The most common ratio I see (and use) is 1 pt. Glue Water: 1.5 pts. Whiting. This generally yields a gesso with the consistency of light cream or whole milk, ideal for applying gesso. Too thick a gesso is more apt to crack.
The Mt. Athos monk with whom I've conversed in the past is asking another question, relative to the above. His gesso recipe, like mine (1 glue: 16 water + 1 glue water: 1.5 whiting) is yielding a gesso with a heavy cream or pudding consistency. He is asking which is more relevant: staying with consistent ratios (even if it yields a thick gesso), or shooting for a gesso consistency of light cream (even if that means adding less whiting). My gesso never yields a pudding-like gesso, so I'm puzzled why he's getting that. Regardless, I would say consistency is more important - applying pudding-like gesso is not good. But then again, gesso is essentially a high PVC paint, and if one too dramatically alters a paint's PVC, isn't that problematic?
I realize all this is complicated by variabilities in ingredients and measuring, environmental factors, etc.; and there is not a simple answer. Nonetheless, I welcome general thoughts on the above, as well as a response to the specific question of which is more important: staying with consistent gesso ratios, or adjusting a ratio (perhaps dramatically) to yield a thinner gesso consistency.
Answers and Comments
What is more important than the water to glue ratio is the glue to pigment ratio. Since water evaporates what remains of the ground is only the glue and pigment. The greater the content of glue in relation to pigment the more the ground exhibits the hygroscopic behavior of the animal collagen glue.
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