The bath ratio of dyeing in dyeing machine is very important to the concentration of dyes and chemicals in dyeing solution. It is also related to dye uptake, fixing rate, stability of dye solution, levelness and reproducibility of dyeing. The dye uptake and fixing rate will increase with the decrease of bath ratio. Of course, the increasing rate of different dyes, fixing rate and dye uptake rate are also different.

Because small bath ratio dyeing can not only speed up the dyeing rate, but also improve the fixation rate to a certain extent, it can reduce the amount of salt, that is, low salt dyeing, and improve the utilization of dyes and alkali agents.

Bath ratio dyeing has the following advantages: reducing energy and water consumption; reducing salt and alkali dosage; reducing dye dosage; improving dye repeatability and leveling. Although small bath ratio dyeing has many advantages, it also has many difficulties. The lower the bath ratio, the more difficult the dyeing will be. It is required that the solubility and stability of dyes used in small bath are better than those used in dyeing. Especially when dyeing dark varieties and multi-dyes are mixed, the dependence of different dyes on bath ratio is different. The contradiction between solubility and stability of dyes is mainly reflected in the distribution tank, because the concentration of dyes in the distribution tank is much higher than that in the dyeing tank.

Another difficulty in small bath ratio dyeing is leveling, which requires good dye circulation and application equipment of the dipping equipment.