Precious Pieces uses natural sizing materials such as a mixture of collagen and myoban alumstone to improve the surface strength, water resistance and wet strength of the washi parchment. The sizing agent covers the cellulose and forms a film which is water-repellent.

All parchment can be made with internal or surface sizing treatments.

Internal sizing (saizu):

Wet strength Internal sizing used in papermaking at the wet vat. By making the paper web more hydrophobic, the sizing agents influence dewatering and retention of fillers and fibers in the paper sheet. Next to paper quality, internal sizing agents’ main effect is on runability of the paper machine.

Surface sizing (do-sa biki):

Surface sizing solutions consists of mainly modified starches or sometime other hydrocolloid as gelatine and a surface sizing agent. Surface sizing agents are amphipathic molecules, having both hydrophilic (water-loving) and hydrophobic (water-repelling) ends. The sizing agent covers the cellulose and forms a film, with the hydrophilic tail facing the fiber and the hydrophobic tail facing outwards. This creates a water-repellent situation. Sizing improves the surface strength, printability, and water resistance of the paper surface. In the sizing solution, optical brightening agents (OBA) may also be added to improve the opacity and whiteness of the paper surface.