Grain plays a major role in how paper handles and works. It is worth taking a little time to understand this important characteristic.
Most of the materials that come to the mending department will be made of paper or board that has a definite grain direction. Practically all papers and boards used to make repairs or protective containers also have grain, sometimes called “machine direction.”
Paper and board tear and bend more easily withthe grain than againstit. Think about tearing a clipping out of a large newspaper. The tear from the top of the news- paper is fairly straight while the one from the side is often extremely ragged. This means that the grain of the news- paper goes from top to bottom, or is “grain long.” The printing press prints on rolls of paper and the grain is al- ways along the length of the roll, not across the width. (See also “Overview of Western and Japanese Paper” in section 4, p. 76, for more information about papermaking.)
Any procedure that calls for folding and creasing will turn out much better if the crease is along, or with, the grain. Going back to the newspaper example, the fold between two leaves is with the grain and is neater than the one that folds the newspaper in half, which is against the grain. At the second fold, the fibers of the paper may be broken and fuzzy.
GETTING STARTED Fig. 2-27
Fig. 2-28
Fig. 2-29
This effect is greatly magnified when heavier papers or light boards are folded, with creases made across the grain significantly more ragged than those made with the grain. For neatness, and to prolong the useful life of preservation enclosures, the folds should be with the grain whenever possible.
Testing for Grain Direction: Paper
There are several tests for telling the grain in paper.
Manufacturers often mark the grain direction on the packaging of their papers by underlining one of the numbers indicating the size of the paper. A ream labeled 8½" × 11" is “grain long,” that is, the paper will fold in half more easily the long way, resulting in a folded sheet 4.25" × 11".
Chain Lines.Many papers have lines that are visible when the sheet is held in front of a light source. The very closely spaced lines are called “laid lines.” The widely spaced lines at right angles to the laid lines are called
“chain lines” (fig. 2-30). In handmade paper,the grain is always parallel to, or “with,” the chain lines.
On machine-made paper,chain lines are made artifi- cially and the grain could go either way. By tradition, the chain lines run in the machine direction, with the grain, but it is prudent to confirm this with one of the follow- ing tests.
Bending. Curl the sheet over in one direction and then in the other direction, pressing and bouncing gently with your hand. Note which way bends more easily. The direction with the leastresistance is parallel to the grain (figs. 2-31 and 2-32).
The next two tests are suitable for new materials only, not for documents or book pages.
Moisture.Wet the corner of the sheet, just along the two edges, with a cotton swab (fig. 2-33). The grain is parallel to the edge that stays smoother. The other wet edge will curl and ripple (fig. 2-34).
GETTING STARTED Fig. 2-30 A sheet of laid paper held against the light
Fig. 2-31
Fig. 2-32
Fig. 2-34 Fig. 2-33
Tearing.Tear a test piece. The paper rips easily with the grain. Ripping against the grain offers more resis- tance and produces a ragged tear. The grain is parallel to the straighter tear (fig. 2-35).
Testing for Grain Direction: Board
Place a piece of museum, bristol, or binder’s board on a flat surface; place your thumbs under the board and your fingers on top and bend the edge up slightly (fig. 2-36).
Turn the board 90° and try this on the edge at right angles to the first. It is better not to look at the board;
instead, let your fingers tell you in which direction the board bends more easily. That is the grain direction.
Sometimes it is difficult to determine the grain of laminated boards like museum board because the board is made up of several layers (plies). As with plywood, the grain of each ply alternates in order to make the board as stable as possible. These boards can usually be used in either direction.
For applications where grain direction is important, cut a piece of the laminated board and brush paste or PVA mix on it. Let it dry. Observe how the moisture dis-
torts the board. The grain goes in the direction that stays straight; the board is “against the grain” in the curled direction (fig. 2-37).
After determining the grain direction, it is helpful to draw a pencil line on the leftover board or paper, near the edge. This saves time in future when looking for a piece of the right size and grain direction.
Testing for Grain Direction: Cloth
The grain of cloth is along the length of the bolt, parallel to the selvage. It is the direction of the warp threads.
However, this is not always obvious in scraps. The surest way to know the grain is to preserve the selvage on cloth that has been cut from the bolt. Form the habit of cutting cloth in pieces the whole width of the bolt (fig. 2-38).
Then cut the quantity needed for the job at hand from that segment, starting at one edge and making sure to leave the selvage on the other edge of the piece until it is used up.
GETTING STARTED Fig. 2-35
Fig. 2-36
Fig. 2-37
Fig. 2-38
If a usable scrap with no selvage is produced, make a pencil line on the back near the edge indicating the grain direction before putting it away.