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Old 16-03-18, 10:27 AM
Chris__Leach Chris__Leach is offline
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Join Date: Mar 2018
Location: Ireland
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Default Making an eggshell coloured gesso

I am in the process of a miniature drawing project and I need to make up some more gesso'd oak blocks. I needed 196 blocks altogether originally which, when finished, had a lovely eggshell colour to the gesso. Due to various different criteria I now need to remake another 35 gesso blocks. I have now tried twice the second time using what I believed to be the same whiting but both times the colour of the gesso is bright white, not the eggshell colour I had on the initial batch. Does anyone have any advice regards remaking the gesso so it has a similar eggshell finish? Can I perhaps make up another batch of gesso with pigment and put another layer over the batch that are 'too white'? Or would you do the 35 from scratch? Any questions please contact me. Thanks
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Old 17-03-18, 05:23 PM
Koo Schadler's Avatar
Koo Schadler Koo Schadler is offline
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Join Date: Dec 2003
Location: Alstead, NH & Zirahuen, Mexico
Posts: 316

Hi Chris,

Various "whitings" (either gypsum or chalk) can definitely vary in degree of whiteness, from bright white to many versions of off-white (pinkish, yellow, grey tints, etc). That's why, as you've unfortunately learned, if you need consistency in the appearance of a gesso ground use all the same batch of whiting.

Yes, you can tint a fresh batch of gesso with pigments to approximate the color of the other gesso. I recommend against using powered pigments to tint and would say use commercially dispersed pigments instead. When adding dry pigments to gesso it's easy to end up with mini aggregate clumps of pigment that, either when you brush on the gesso or sand the dry panel later, get dispersed by your brush or sanding and leave a streak of color. Natural Pigments, Guerra, Kremer all make aqueous-based, commercially milled pigment dispersions; the color is better dispersed than you’ll probably ever achieve by hand (unless you use a glass slab, muller and lots of elbow grease, in which case you could mill by hand). The main point is: add a well dispersed pigment to your gesso and blend in well. (BTW, if blending stirs up too many air bubbles, let the gesso sit overnight in the fridge to calm down, then rewarm the next day. Letting gesso sit overnight is one of the keys to making good gesso).

The challenge will be matching the colors - it's not going to be enough to just add pigment to the new gesso and compare it to the original panels. For a good color match you’ll have to apply as many coats as you anticipate applying in the final version to a test panel, then let it fully dry (the color can change a lot depending on number of layers, and if it's moist or dry).

Gesso adheres to a support via dispersive and mechanical adhesion. Some folks believe adhesion occurs primarily through dispersion and that mechanical is less important. In my experience mechanical adhesion (when two substances interlock – think velcro or sewing) is very important to the longevity of both gesso on a support, and egg tempera layers to gesso. You will not get as good mechanical adhesion if you apply the new gesso to already dried gesso (versus onto a fresh, porous support) – but how critical this is, I can’t say (depends on your expectations for longevity; what sort of conditions the artwork is kept under; i.e. changing humidity always making things more problematic, etc). If you very roughly sanded or scored into the old gesso before applying the fresh batch that would encourage more mechanical adhesion; or just start on a fresh support.

Good luck and let us know how it goes, please!

Koo Schadler

Last edited by Koo Schadler; 17-03-18 at 05:36 PM.
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