To use a dye produced by fermenting a raw material such as indigo, the dyeing process must be performed in a hot and humid environment so as to activate the enzyme, so the work is generally done in the summer.
藍などのような原料を発酵させて得る染料の場合は特に酵素の活性を高めるために高温多湿の環境で染色を行わねばならないため、作業は夏ごろ行われることが多い。