Gum Arabic in Vernice Bianca Ground Question


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I'm preparing my first ground layer and am going to do the Vernice Bianca approach. Here's the instructions from a previous post:

"Dissolve in a water bath 25 grams of arabic gum in 100ml water, half tablespoon of honey and one quarter tablespoon of sugar. Let it cool. Then beat the white of an egg with a fork till it forms a "snow" and let it stand for 14 hours. Take the liquid substance that forms in bottom of the container egg and add it to the first solution and filter."

The part about adding 25g of Gum Arabic and disolve in 100ml water implies the Gum Arabic would be solid pieces. My local art store sells Gum Arabic in liquid form, so that's what I bought. Do you think this will be acceptable, and further, how much liquid stuff would be the equivalent to 25 grams....1 tablespoon, a couple tablespoons, or is it not that critical?

Thanks, John

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I'm guessing what matters is whether that liquid gum arabic contains any chemicals that might interfere with what you're trying to do somehow. I kind of doubt it, because the artists are probably doing similar kinds of things with it and need it to be able to dry.

I'm also willing to suggest that the exact ratio doesn't really matter either, because there are different versions of the recipe and some people just use the egg white without any gum arabic or sugar at all, and seem to be successful with it. There were some discussions in the past here about whether the sugar should really be in there. I don't recall what the conclusions were, but plenty of Vernice Bianca has been made and used containing sugar and it seems to have worked, so I don't know if I'd worry about that either.

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The principle of ground is to seal the wood. The egg white is a good medium as a sealer when dried.

Then.... the question should be why do we add Gum Arabic and Sugar? And how much is needed?

Gum Arabic is often used as adhesive agent. In Sacconi's book, it also mentioned that Gum Arabic will improve the layer coating because of the adhesive property. If your egg white is already sticking to the wood properly, do you still want gum Arabic in your solution? It is up to yourself.

According to Claudio, the translation of "Sugar and Honey" is a bad translation from Eric Blot. It should have been Molasses, a less refined form of brown sugar. It is much more hydropscopic than regular white sugar. Now.. why do people add sugar to the egg white? In baking, sugar is added to the egg white before beating so the foam of egg white can solidify and stablize more easily. Keep in mind that Tony did not have Kitchen Aid appliances to help him beat the egges. I used an electric beater to beat my eggs. It takes a good 5 mins at max speed to get to the desired results. Imagine how much it will require from your arm. Then what is the difference between sugar and brown sugar? This can be explained from your every day chocolate chip cookies. If you like your chocolate chip cookies crispy, then use white sugar. If you like your chocolate chip cookies soft and chewy, then use molasses. This will have simiar effect on your grouind as well. If you want a hard ground, then use no sugar. If you want a slightly softer ground, then use white sugar. If you want a very soft ground, then use molasses.

It all depends on your personal tonal preferene and what ever works for you.

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The main difference between dissolving gum arabic crystals a d buying the prepared stuff is that the prepared gum arabic contains some plasticizers (probably glycerin) In which case you can cut back on the honey which is supposed to act as a plasticizer

Oded Kishony

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Quote:

The part about adding 25g of Gum Arabic and disolve in 100ml water implies the Gum Arabic would be solid pieces. My local art store sells Gum Arabic in liquid form, so that's what I bought. Do you think this will be acceptable, and further, how much liquid stuff would be the equivalent to 25 grams....1 tablespoon, a couple tablespoons, or is it not that critical?


2 tablespoons of your liquid gum arabic dissolved in 5 tablespoons of water should give you an approximation of the recipe that calls for 25 grams of gum arabic dissolved in 100 ml of water. I'm assuming that the gum arabic you bought is fairly concentrated (thick) and I adjusted the water to account for the water that is already in your gum arabic.

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Could the gum arabic in the ground contribute to the adhesion of the overlying varnish as well? (Though egg white is also said to be not very sticky, it seems to stick fine to wood.)

Since the gum is an emulsifier, it allows oil to be incorporated in the mixture (like egg yolk in tempera painting). Just wondering here but might the proportions of egg white, gum arabic and linseed oil be adjusted to make a more gradual transition from the hard, brittle egg white to the softer varnish? Maybe a way of continuing the fat over lean principle into the ground...?

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