Abstract: There is effected an accelerated direct neutralization in-situ of the substrates which are impregnated with alkaline hydroxide which is free or fixed on the cellulose, by contact with a neutralizing fluid containing carbon dioxide in a gaseous, aqueous or combined phase, this fluid being introduced in accordance with requirements related to the quantity of alkali to be neutralized. The process may be used in the textile industry in continuous and discontinuous treatments and is adaptable to all types of textile machines employing an aqueous method.