This natural dye is finely ground Sappanwood, Cæsalpinia punctate, which  is found throughout east Asia and is sometimes known as Eastern Brazilwood. Originally, Brazilwood was an old-world dye, that the country of Brazil was named after, when the tree was found growing there.  The trees was historically over-harvested in Brazil, but this Eastern Brazilwood grows widely in Asia and is a sustainable source. 

This wood is high in tannin and a colorant known as Brazilian. It produces warm reds when dyed at a 20% WOF and deep crimson reds when dyed at 50-100%. The dyebath can be used multiple times for lighter colors. Wide variations in color can be achieved (orange to berry purples) when the pH level of the dye bath is manipulated. Fabrics dyed with brazilwood are fast to washing but not quite as lightfast as some other natural dyes.

The higher amount of Sappanwood to fiber, the stronger the color.

Brazilwood is sensitive to the pH of the water; acids (vinegar or citric acid) will make the colour more orange and alkalis (soda ash or calcium carbonate) will give you blue reds and purples. Brazilwood is also sensitive to iron; a pinch of iron will turn brazilwood towards lavender.

Using a little chalk (calcium carbonate) or soda ash to make the dye bath more alkaline can make a very big difference to the color of the dyed item. If you don’t use chalk or soda ash when dyeing wool with brazilwood, you will probably get orange. If you add a pinch of chalk the colour turns to berry and red hues; adding more chalk (1/3 to ¾ of a teaspoon) turns the wool toward crimson/burgundy or berry.  Add the chalk to the dye bath after you have strained the brazilwood and before adding the wool.  This is very finely ground wood, so I recommend straining the dye bath water well before putting your fiber in, or putting the sappanwood in a very fine cloth in the pot so you can easily take it out. 

You can later use a chalk or soda ash dye bath to change the color of wool that turns out orange without it, but it just may not change to quite the color it would have if the original dye bath was made alkaline.