This part of ISO 5350 specifies a method for the estimation by transmitted light of the visible dirt and shives in laboratory sheets prepared from pulp. It is, in principle, applicable to all kinds of pulp, although it is mainly intended for pulp that is not manufactured in sheet form. This part of ISO 5350 can also be applied to mill sheeted pulp, if the sheets have high grammage or are very opaque for other reasons, in which case ISO 5350-2 is not applicable. This part of ISO 5350 is not intended for recycled pulp. NOTE Shives in mechanical pulp are usually determined by means based on screening or optical analyses. Some grades of mechanical pulps can cause problems in sheet-making or inspection, which makes this part of ISO 5350 impractical.