Last summer I recorded my investigations into replicating early 19th century book cloth using XSL pigments. One difficulty was achieving an even coloring, and several commenters indicated I should scour the fabric, rather than just wash it. Finally, I had a little time to try this, and although I haven’t had a chance to do more dying, tests with wheat starch paste have been astounding.
I boiled 1.5 yards of Springs Creative 45″ unbleached muslin (133 x 72 thread count, .007″ thick, $4.00 a yard) for two hours in a stainless steel pot, using 1 tablespoon of soda ash per 6 cups of water. Since it smells a bit, it is advisable to have a externally vented exhaust hood. A long stirring stick is necessary, as are rubber gloves.
Keep a close eye on the boiling muslin. I used large pieces of cloth, for future use as covering material. As the water boils, hot areas form bubbles under folded and wrinkled areas. Then when you stir, they get released and the pot bubbles over, or worse, spills on you. I stirred the pot every 15 minutes so that all cloth surfaces were exposed to the scouring, and adjusted the temperature as necessary to keep an even boil.
The scouring raised the pH of the cloth from around 5 to 7, though this was measured with testing strips and is likely not super accurate. Soda ash is around 10 or 11 pH. The scouring removed oils, waxes, and pectic substances. The cotton fibers swelled and softened during the process.
The difference in adhesion between the scoured, washed, and untreated samples is remarkable. All were pasted with Aytex P wheat starch paste onto a piece of Mohawk Superfine, with the same weight during drying. I testing the adhesive strength by pulling the fabric away from the paper at 180 degrees. The scoured sample delaminated the paper, while the washed sample (hot water, a tiny bit of Seventh Generation Free and Clear detergent, industrial washing machine) and untreated sample released without affecting the surface of the paper. I tried this two more times, and the results were the same. In a separate test using EVA all the samples delaminated the paper. I’d like to get a push-pull gauge to quantify the adhesion a bit more rigorously. Of course, there may be circumstances where a weaker adhesion is desirable.
But for most book conservation applications — spine linings, board slotting flanges, hinges, sewn stuck-on endbands, covering material — strong adhesion is desirable.