Methyl cellulose is a paste of conservation quality. Methyl cellulose ~ MC ~ is a natural sticky product. Cellulose, in some form or other, is the adhesive that binds together the fibres of plants.
MC is normally sold and supplied as a fine white powder. When mixed with water it forms a paste which bonds well with paper, leather, and similar materials. Starch pastes ~ from wheat or rice ~ are regarded as being slightly stronger, but MC is readily obtainable ~ has many advantages ~ is economical ~ and it is a perfectly good adhesive for most pasting tasks. (I use the word paste to imply that glue has a rather stronger 'stick'. Cellulose paste is quite sticky enough for many tasks.)
Most wallpaper pastes contain methyl cellulose, with the addition of other chemical agents to help dissolve it in water. They may also contain small amounts of fungicide ~ to prevent mould ~ and so their use must be treated with caution. MC is available at many on-line outlets, and some is listed as being of medical purity.
Its main advantage over starch pastes is that the latter require heating, and do not keep for longer than a few days. I have had a jar of MC paste 'on the go' for several weeks.
There are numerous recipes and techniques for mixing the paste from powder. A good starting point is to make a five per cent mix. Take five grams of paste powder with 100 grams of clean water, and mix them thoroughly. That sounds easy, but there are four small problems ~ they are easy to overcome ~ do not be put off from making some.
MC is a tricky power to mix with water. Firstly it needs hot water to ensure dispersion, and then cold water to dissolve. One suggestion is to shake up 5gm of powder with 50ml hot water until flakes are dispersed, then add 50ml of cold water to dissolve the solids ~ whilst stirring. I find using a jam jar with a tight fitting screw lid is useful. Aim only ever to half fill it and the content can then be really shaken about a great deal with wiggling wrist muscles. If 5gm to 100ml is too thin or thick then adjust accordingly ~ although it is easier to make it thinner. Leave it to settle ~ overnight if possible. Small bubbles may remain ~ but they do not seem to have any poor effect.
5gm is a small quantity. Much too little to be able to weigh on a kitchen scale. A good postal scale is accurate to the nearest gm. A jeweller's scale is ideal ~ who has one of those? (I recently bought one for less than £10 ~ I find it a useful, if rarely used, tool.)