chemists and colorists preferably disperse dyes are used either with the acid dyes or with the cationic 34 basic 34 dyes when cationic 34 basic 34 dyestuffs are used it is necessary to include a small amount i e up to 10 by weight calculated on the weight of bath of an acid substance and water to achieve the desired color penetration and build up of shade such materials include various organic acids or which the following are representative maleic fumaric cinnamic phthalic oxalic crotonic succinic naphthalic benzoic malonic glutaric adipic suberic sebasic azelaic citric acetic formic dichloracetic trichloracetic propionic acids of these acids maleic fumaric cinnamic and phthalic acid are preferred the exact reason for the presence of an acid is not now understood but such materials are necessary in order to adequately dye type 470 472 and 473 nylons with cationic dyes the duration of the treatment with alcohol and dye can also be varied over a relatively wide range the time is normally selected for any particular situation to optimize the bulking and other desired properties as well as achieving the requisite depth of shade after the treatment with alcohol and dye it is necessary to wash the fabric in hot water for example at about 40 u00b0 to about 100 u00b0 c and then to soap and finally wash in hot and cold water the washed fabric is thereafter dried in any convenient.