In this case, the wood is treated with sodium hydroxide and sodium sulfide. This process was developed about 1885. Just about any kind of wood can be used. Normally the pulp is not bleached. Conifer woods are commonly employed.
Tall oil is a by product of pulping.
This material contains resins and fatty acids. Resins, gums, starches, or rosin can be added as sizing agents or talc or clay can be added as fillers at this stage. Alum is also added to bind the sizes to the fibers. Dyes may also be added. A vacuum under the screen sucks excess water out.