Japanese paper is commonly used in book repair because it is thin and strong. For joint and hinge repairs, the paper is cut into thin strips, just wide enough to cover the damaged areas. Don Etherington suggests using morike for the outer hinge because it comes in a variety of colors to match the cloth or leather. He also advises coating the morike in Klucel G because it darkens the color and prevents the paper from fraying when rubbed.*
These strips are adhered to the area with either polyvinyl-acetate (PVA) or a starch paste. (PVA is used for leather bindings or book covers, and paste is used on any part which touches the text block). It is crucial to remember to treat the inside of the hinge first. Even though the Japanese papers are thin, sometimes they create enough swell to split a previous repair on the outer hinge.
The following images depict basic Japanese tissue repair on a leather binding. This particular book had a leather inner and outer hinge, and almost no joint. Because of this, use caused the leather to crack (Top: cover view; Bottom; inner hinge).
PVA was used to attach thin strips of Japanese tissue to cover and support the damaged areas. After drying, the tissue was toned with acrylics. Then I applied SC 6000 to the toned area on the cover. The SC 6000 will protect the acrylic pigments from cracking with use, and also ads a slight shine, which mimics that of the leather (Summer 2009).
*Use of Japanese Tissue in Conservation, presented by Don Etherington as part of the CBBAG Restoration and Repair: Part of the home study programme.