In this technique, dyed woolen thread is removed from the beaker containing ammonia. Then, the ammonia solution is made slightly acidic and boiled with a fresh piece of woolen thread of 20 cm length. It is boiled continually until the color is stripped by the woolen thread. The dye is again removed from the thread by using 1 N ammonia which is then filtered by a small piece of cotton. The filtrate is concentrated on the hot water bath.