Among the days of the week, Saturday is considered holy by Hindus, on this day devotees attend temples to worship Gods or perform rituals at home. Physical cleanliness, particularly washing hair is a prerequisite to participate in the prayers, thus Saturday became a shampoo day.
From ancient times, Soap nut trees were cultivated for the berries that contain saponins or natural soap. The dried Soap nuts either whole or crushed were sold in shops and daily markets. Handful of crushed dried soap nuts are soaked in hot water to extract the brown and frothy bitter juice to apply to the hair as a shampoo. Soap nut extract is very effective in removing oil from the hair since most Indians use coconut oil on a daily basis in grooming their hair.
Besides Soap nuts, dried pods from Accacia tree locally known as Shika-kai are also used to make a paste to apply to the hair as a shampoo. While the Soap nut extract irritates eyes giving red eye, paste from Shika pods is mild and user friendly though less effective as a shampoo.
With the advent of user friendly commercial shampoos and hair conditioners with choice of fragrance, the use of dried soap nuts and Shika pod paste became almost extinct. People can still get the dried soap nuts and Shika pods at local markets, though now ready made extracts are sold in bottle as herbal organic shampoo at exorbitant prices.
Saturday is a holy day and still a shampoo day but no more red eye from bitter Soap nut juice.