These may be partly replaced by Natal bark, valonia, and quebracho respectively.
There are several grades of valonia, the best going to Russia, Austria, and Italy.
valonia was first used in England about the beginning of this century.
Oak bark and valonia contain some of the properties of both classes of tannins.
It is considered slightly inferior in strength and colour to the Smyrna valonia.
Greek valonia is greyer in colour, and contains 26 % to 30 % of tannin.
The Smyrna or Turkish valonia is best, and contains 32 % to 36 % of an almost white tannin.
Greek valonia is obtained from many parts of the Archipelago and mainland.
The union of valonia and knoppern is that in most general use.
The acorn-cups of one species are brought from the Levant under the name of valonia, and used in tanning.