The most vital substance in marbling is Ox-gall. It is the bile juice of an ox, but the bile of any animal can be used ( even fish-bile)
Yes, it sounds absolubely Disgusing, but it really is not . It is just a fluid, ranging from dark brown to near colourless , which sometimes smells bitter.
The gall's effect is twofold
I) it makes the colours spread. The more gall is added, the more it spreads.
II the gall has this wonderous property , that is, no matter how much the colours are manupulated on the size, they would not mix.
For example, if you drop on yellow, and then blue, the colours would stay seperate. if you take a stylus, and draw it through them, they would still remain distinct.
The primary principal regarding gall is this. More gall makes the colours spread more, but also makes them paler. Each sucessive colour applied needs more gall than the last. (however, some colours may need more gall than others. )
The gall also differs in strength. In my experience, the darker sort is generally stronger.What one type of gall does with a tablespoon , another can do with six drops.
The gall that us sold in art shops is passable, But some is so weak as to be of no use at all. Therefore, if you have tried all kinds of gall, and none work satisfactorily, order some from a marbling suppler, like Iris nevins or Colophon
If you are so daring as to attempt to obtain the gall "fresh from the cow", I shall give you some instructions .
Take the gallbladders of any animal, preferably a cow/ox. they may be bought from a butcher, or slaughterhouse. the cost for them is slight, if not nonexistent, as the gall is considered waste. The baldders MUST have the fluid within them- this is the gall that we want
Now, puncture the galls, and let them drain into a vessel. Add to this alcohol, about a quarter of it's volume. let the fatty matter settle from it, and then strain it. After a bit of ageing [ if you wish to do so] it may be used.
I have successfully prepared the gall of chickens in this manner, but the gall was a bright green in colour!
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There are alternatives to gall. However, they are mostly an apolology to the real stuff.
The first of them is photographic wetting agent. It is primarlay used on acrylics, as the stuff that comes from the cow is too weak. The sollution is used watered down, as it is too strong neat. In my experience, ( using it with watercolours) it is quite unpredictable, and difficult to control. The colours sometimes spread out uncontrolabaly, or fail to spread altogether.
The second class are preparations of soap. They have generally included washing up detergent, and solutions of soap. Their expanding power is often stronger than gall, but it comes at a price. Firstly, the colours tend to have fuzzy edges if you use too much of it.
The second is rather curious. The colours, when mixed with a large amount of the solution, tend to go all stringy and goopy after a while.
The solution ( which I shall discuss in greater deatil under "italian" ) is made by dissolving soap in water , sometimes with a quantuty of alcohol added.
