One of the processes in restoring scrolls and paintings is the making of the paste. This paste can be used on such materials as - paper, silk and wood, in other words it can be used on fragile materials but also much stronger objects such as sliding doors or wooden screens. Its consistency will be altered by adding water to whatever strength is needed. The paste is clear and transparent, it will not mark the delicate silks or papers, it is also 'reversible'. Meaning that may be after a century or two when the scroll has become worn, it can then be taken apart and renewed with new papers and silk. To me it is somewhat of a 'magic' paste, and when you think of all the glues on offer for all types of materials to have one single paste is simplicity itself. For the Japanese Hyogushi or conservator, this paste is one of the most important aspects of his work.
It is made of wheat starch, and is a by-product from the gluten makers who extract the gluten to make cakes and dumplings. The gluten is extracted leaving the starch behind at the bottom of the pan of water, the extraction process is long and complicated, suffice it to say that there are three products that emerge from the water that has extracted the gluten. Firstly, uwa-miza, which is of no use except as a covering of water for protecting the paste; secondly jin-nori, a watery glutinous paste which is sometimes used by other crafts such as dyers. But it is the third and final layer shofu-nori- almost pure wheat starch this is the stuff the hyogushi will use.
As already mentioned the paste is used on a limited number of materials; the combinations being as followed; paper/paper (linings, laminates); paper/silk (linings), paper/wood (rollers/wooden lattices); silk/silk (braids for scrolls), and wood/wood (pommels for scrolls). And of course it can also be used as a size or fixative.
The process of making or cooking- the paste is done on the stove, water is added to the starch and it is gently and methodically stirred for about one hour, its consistency will change over this period. As the paste becomes 'stiff' it is important to whip or stir it vigorously to get the required viscosity, which is often much better if the paste is made in the cold months of winter.
The making of aged paste or Furu-nori; A great pot is made of this, there are several cookings of the paste, and each batch is put into the pot then the pot is tied with persimmon treated paper, and then left for a year. The pot is then opened, the old water poured off and new water added. This happens every year for 10 years, until it reaches its final stage and can be used. This ten year period is the length of an apprenticeship in the studios of the conservators and marks the end of the apprenticeship.
There is a difference between the old and new paste, the old paste has weaker bonding abilities (don't we all) but the old paste (furi-nori) is able to laminate more sheets of papers of a particular kind without producing the brittleness and stiffness of the new paste (shofu nori), and because of this difference is used mostly on the hanging scrolls, which are of course rolled up or unrolled for use, and need to hang straight when displayed. Also, because aged paste is so much weaker, a secondary method is used, which is the beating of the papers together with a brush called uchi-bake which is made from hemp palm fibres. The brush strikes the scroll at a certain angle and 'meshing' of the papers take place to which the furi-noro has been applied.
Old paste can be sieved twice, once through a horsehair sieve and secondly a fine silk sieve.This is one of the pots, an 'Ali Baba' type of pot, very suitable for growing plants in but unfortunately it has no hole in the bottom for drainage but is a good collector of rain water!
A rather beautiful bowl used for the paste, though its first use is for the grinding of minerals.
Fresh paste is very stiff and will have to be cut out in lumps, it is then put through a horse-hair sieve and kneaded with a paste brush.
ref; Manufacture and Use of Japanese Wheat Starch Adhesives in the Treatment of Far Eastern Pictorial art.....