When all is ready the bath is heated up, the swatch put in and the work of the test entered upon.
Students are recommended to make experiments on such points as:--
The shades obtained by using various proportions of dye-stuffs.
The influence of various assistants: common salt, soda, Glauber's salt, borax, phosphate of soda in the bath.
The influence of varying proportions of mordants on the shade of dyeing.
The value of various assistants, tartar, oxalic acid, lactic acid, sulphuric acid, on the fixation of mordants.
The relative value of tannin matters, etc.
Each dyer should make himself a pattern book into which he should enter his tests, with full particulars as to how they have been produced at the side.
It is important that a dyer should be able to make comparative dye-tests to ascertain the relative strength of any two or more samples of dyes which may be sent to him.
This is not difficult but requires considerable care in carrying out the various operations involved.