Gum Arabic as gouache medium or glazeApproveRejectUn-ApproveSubscribeUn-Unsubscribe
Question asked 2023-02-20 10:50:06 ...
Most recent comment 2023-03-05 10:11:43
Gouache
I paint in gouache, mostly tubed, but also the Lascaux bottled "tempera" gouache. I am painting on linen on cradled birch panels with linen applied with either dilute PVA glue, or rabbit skin glue (RSG) depending on the stiffness of the linen. The linen is sized with RSG and then 4-10 layers of true gesso is applied as a ground. I want the linen for the texture.
I've started using gum arabic (GA) as an extender/glaze and wonder about long term cracking of the "glaze. Some of the layers are almost all GA (or 50% GA to water) as I am going for very dilute washes similar to Chinese ink paintings, and then more pigment as the subject matter comes to the forground. There is quite a bit of erasure in my process, using sponges and water, much reworking and layerring. The ground generally is preserved although to be honest I sometimes get down to the linen, or close to it. The look of "process" is important.
Q1: I suppose I assume that the interlinking of layers is preserved as all the layers are water-soluable. For example a very dilute initial glaze of 50/50 GA to water on true gesso binds well, and then subsequent layers with perhaps 100% GA glaze medium with greater amount of gouache/pigment, then perhaps pure gouache on that, possibly knocked back with a very water-wet soft brush. So you see there's a lot of back and forth. (I've noticed that the GA glaze is slower to "reactivate" that a pure gouche area and I use this to layer glazes to create certain effects.) My long winded Q basically is: Does my assumption that the universal water soluability of the various layers is sufficient to create a bond between those layers, despite different amounts of GA proportionally, application of water to erase, or pure gouache (no GA at all)?
Q2: Gum Arabic is expensive. A little Windsor Newton 2.5 oz bottle is about $12. A Schminke 200ml bottle is a bit cheaper per unit, but not much. I've seen a thread on using photo emulsion GA on another site but I cannot find anything on the use of Food Grade GA. You can get a gallon for the $50. It's similar in viscosity, and color. I've noticed that the Schminke contains "biocidal products", which leads one to conclude that there is an issue with GA "going off". It smells sweet, and "food-y". I havent tried it yet but as I am starting much larger paintings I need to find a source of cheaper GA, unless you tell me my method above will lead to everything falling onto the floor in a few years. Hopefully not.
If necessary can I add a biocidal product in small amounts to preserve the food grade GA? What would that be? a few dropd of bleach?? Sounds iffy...
Thanks!
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