The basification or the addition of alkali to increase the reactivity of the chrome to the collagen fibre can be done by a variety of methods. The use of a basifying solution such as sodium bicarbonate will call for many careful additions at frequent intervals if the pH is not to go too high and causes too much chrome fixed on the surface resulting in poor grain properties and unlevelled dyeing etc.
This method was however used for many years and is still used today in some productions. The use of mechanical dosing pumps removes some of the human error risks with this method. The best method of basification will see the pH rise slowly and evenly throughout the tannage run under the influence of time and temperature.
Self or automatic basifying agents have been developed to achieve this gradual increase of pH throughout the tannage run. Some chrome powders are available with a basifying agent 'built in' to the chrome powder.