[Scriptoris] Natural pigments question

[Jennifer Baker]

I have never painted with natural pigments before, but at KWHSS I was 
given some small samples to try.  I have 4 vials, each about an inch 
tall and 1/2 in diameter.  The pigments are Verona Green Earth, Italian 
Yellow Earth, Venetian Red, and Italian Burnt Umber.

I know I need gum arabic or some other binder, but I don't know how much 
to use in proportion to the pigment or water.

Can any one offer any advice?  I'd really like to experiment a bit with 
these, but I don't want to waste them because I don't know what I'm doing.

Many Thanks in advance,
Alicia