The production of viscose is briefly described here. Each of the main stages is distinguished in italics. The cellulose used for viscose production usually comes from specially processed wood pulp (a different grade to that used for paper making). The pulp is saturated with sodium hydroxide a steeping process forming 'soda cellulose' followed by pressing and shredding to increase the surface area of the cellulose. The resulting material is usually referred to as 'white crumb' at this stage. The crumb is aged by standing in air where partial cellulose oxidation occurs yielding lower molecular weight products of cellulose. The aged crumb is then mixed with gaseous carbon disulfide forming xanthate ester groups (giving the name 'Xanthation' to this stage of manufacture) giving the crumb a yellow colour. The yellow crumb is then dissolved in aqueous alkali solution resulting in the previously insoluble cellulose polymer becoming water soluble. The high viscosity of the xanthate solution lead to the descriptive term 'viscose'. The viscose is then allowed to 'ripen' during which time some rearrangement and redistribution of the xanthate and hydroxyl groups occur. Filtering then removes any undissolved materials and a degassing procedure removes any trapped air bubbles in the 'viscose' solution. In the spinning process, the viscose is forced through a spinneret forming a fine filament which is then passed through a solution containing sulphuric acid, sodium sulphate and zinc ions. Many things happen during this stage including the removal of the xanthate ester groups and the regeneration of the cellulose hydroxyls (making the cellulose insoluble in water once more). The resulting fine filaments are stretched, a process which aligns the polymers of the fibre giving the desired finish to the textile fibre. Several final washing steps ensure no water soluble residue remains. The viscose can then be cut into staple length fibres in a rotary cutter and can then be processed in a similar fashion to cotton if necessary.