The Choice of Paper in Book Production When deciding paper choice for book production, factors such as bulk, coating or longevity are the first criteria to determine. The type of paper that is appropriate for any particular title must be given careful consideration. The brand of paper is somewhat less important. Vital to the decision making process is an understanding the various properties of paper products. That is, whether the stock should be coated or uncoated, woodfree or mechanical, and which characteristics of the job determine the final choice. Properties of paper Most paper is made from trees, but any cellulose fibre may be used. High grade writing paper often contains cotton fibre. Other fibre sources include grain stalk residue after harvesting, or even cannabis hemp. Recycling is also an important source of fibre, but due to the high cost of processing and wastage, recycled paper will often be more expensive that made from virgin pulp. The first paper was made from papyrus reed, harvested from the banks of the Nile, hence the name. Most pulp manufactured in Australia is sourced from plantation timber, and any forest content is mainly from sawn timber waste. To understand the most basic properties of paper the paper making process needs to be examined. Woodchips are converted into pulp using two main methods. It is important when making paper choice that we fully understand the process by which pulp is produced. Mechanical pulp, as the name implies, separates the cellulose fibres predominately by mechanical means, resulting in low grade material often with small pieces of tree still intact. Newsprint is a typical example, and many book papers are made from mechanical pulp. Papers made from mechanical pulp may have high acidity, and will discolour, or regress in a relatively short time. They should only be considered when the life of the book is likely to be relatively short, such as a mass market paperback. They are significantly cheaper than other papers. Chemical pulp results from using chemical agents to separate the cellulose fibres. Papers made from chemical pulp are generally a stronger product, with lower acidity, and are therefore unlikely to discolour or regress. The general term used for these papers is woodfree. Woodfree papers should always be used where quality and shelf life is important. Some papers are made from a mixture of both types of pulp. These are referred to as semi-chem papers, and will discolour, but not as rapidly as mechanical stocks. they can sometimes be considered as a cheaper option to woodfrees. Archival papers are those that have no acidity, resulting from the use of quality pulp and alkaline sizing during the papermaking process. Archival papers will have a life expectancy measured in hundreds of years. They can be very expensive, but most locally made woodfree papers are now using alkaline sizing and will last for many years before deteriorating. Coated or uncoated? Coated refers to papers with a clay and calcium carbonate coating, resulting in an extremely smooth surface; important where high quality halftone reproduction is required. Coated papers are made in matt, satin or gloss finishes. These finishes are achieved by the amount of calender used after the coating process is completed. Calendering is the process by which paper is fed through a stack of highly polished metal rollers to smooth the surface. The greater the calendering, the higher the gloss. Coated papers are identified in grades of A1, A2 or A3. These grades refer to the amount of surface coating used. A1 papers are the highest quality and contain more coating than lessor grades. A3 stocks are normally used in magazine production, and usually have mechanical core stocks, and a minimum of coating. A2 papers should be the first choice for book production. They are quality papers that print well and are economically priced. The choice of which coated paper brand is largely subjective, and may be determined by colour, price, or feel. Opacity and bulk may be more objective choices, although generally, there are is little differentiation between the brands. Coated papers will bulk much less than uncoated stocks of similar grammage due to the fact that the coating is a much heavier material than cellulose fibre, and the calender stack also reduces bulk. Uncoated papers are appropriate for straight text printing, or when there is no requirement for exceptionally high quality halftone reproduction. Halftones can be successfully reproduced on uncoated stock, but care must be taken at the prepress stage to ensure that the scans are of the correct contrast and screen value. There is a range of uncoated papers available, starting with mechanical stocks through to high quality woodfree papers. Beyond these are the speciality grades which are rarely used in book production. Speciality grades are very expensive, and more often than not, come in standard sizes unsuitable for standard book sizes. Uncoated papers can vary greatly in opacity, bulk and finish. Mechanical papers usually have better opacity and bulk than woodfrees, and are often off-white in colour, further enhancing opacity. The finish is generally less smooth than woodfree stocks. One final property of paper is that of grain direction. This refers to the parallel alignment of the cellulose fibres during manufacture. Paper will tear more easily along the length of the grain direction, and other processes such as press performance and folding can be affected by the direction of the grain. Particularly where heavier grades and boards are concerned. In web production the grain runs along the length of the paper. When sheeted papers are used, the grain direction is indicated by the second measurement. (A sheet size of 650x910 indicates long grain, and 910x650 would indicate short grain). Most papers are marketed as long grain sheets. In a perfect world, the grain direction should be parallel to the spine of the book. This is not always possible, and cross grain books are fairly common, particularly from web production, and larger formats such as A4 where short grain sheets are seldom available. The exception is that the grain direction of cover boards, endpapers and binding material must always align with the spine. If not, the books will be difficult to bind, and are likely to distort. The substance of paper refers to the weight. This is measured as Grams per Square Metre (GSM). Within each category (mechanical or woodfree, coated or uncoated) GSM is usually relative to bulk. Another important factor to consider is the relationship of paper bulk to finishing. Uncoated papers of 90gsm or less, and coated papers of 100gsm or less can fold as 32-or 48-page sections. Heavier stocks need to fold as 16-page sections, resulting in significantly higher finishing costs. # # # # #