What is it about the paper in paper towels that make them soft, floppy, and absorbent? What is it about a crisp sheet of stationery that makes it perfect for writing a letter?
Some background to begin…
I will begin at the beginning: paper is made from cellulose fibres held together by hydrogen bonds. They is no glue per se in paper. The cellulose fibre comes from plants and different plants yield paper pulp with different properties. In my years as a hand paper maker, I made paper from many plants I collected and cooked up myself from strelitzia to wild ginger. Commercial papers are almost exclusively manufactured from commercially planted and harvested trees, since they are available in the huge quantities needed. The wood fibre is physically chopped up, cooked in caustic to break down the fibre, then washed and blended to turn it into paper pulp.
Coated and uncoated paper
Commercially made paper is divided into coated and uncoated papers. Both paper towels and stationery are what is called ‘uncoated’ paper. Both have a textured surface, in the case of paper towels, it has a very rough surface. There is no coating added to smooth this out for printing.
Sizing is added to change a paper’s qualities
Sizing is a chemical additive that changes a paper’s qualities. It is added to reduce absorbency and to add strength. It is added either to the vat when making paper (internal sizing), or after the sheets are formed (external or tub sizing). On a physical level, sizing fills in the gaps between the paper’s fibres, so that water cannot be wicked up or drawn into these spaces. Paper towels and serviettes don’t have sizing because we want them to absorb liquids.
Unsized paper for paper towels
It is frustrating to write on a paper towel or a serviette since the ink is drawn up as it bleeds into the spaces between the fibres. The lines become blurry and feathery. Serviettes would be terrible for watercolour painting because most of the paint would be drawn into the paper, wasting it. Paper needs a different set of properties for writing and painting.
Sized paper for writing and painting
Stationery and watercolour papers are sized. In these papers, the gaps between the paper fibres is filled up so that the ink or paint sits on the surface of the paper. We can write in clean lines and paint distinct shapes. The lines do not bleed or feather.
What is used for sizing?
When hand papermaking, I sized paper with wheat starch, rice starch, or methyl cellulose (wallpaper paste) in the vat or with gelatine after the sheets were formed. The starches and gelatine left paper soft and floppy while the wallpaper paste gave paper a stiffness and bulk. These suit the both the hand papermaking process and the cotton, abaca and recycled fibres that papermakers commonly use. Commercial papermaking uses different chemicals for sizing, but the job that sizing does is the same: filling up the spaces between the fibres so the paper is less absorbent so your pen line or painted shape sits on the surface of the paper.
What qualities do you need in your paper?
When making paper or choosing to buy paper for a specific print promotions, think about what qualities you need in the paper. There are hundreds of commercial papers available whose fibre, sizing and processing has been planned to give the properties suited to specific purposes. Paper company sales representatives are a mine of detailed information. You don’t need to know all about paper, just start by contacting them and asking questions. Tell them what you want to achieve and go from there. Enjoy!
Commercial paper handmade paper uncoated methyl cellulose cellulose fibre sizing