2 EXPERIMENTAL

2.1 Apparatus

THE DEIONIZED WATER was prepared in the Research and Testing Lab by passing tap water through two cation exchange cartridges (Universal Cartridge, no. 1506–20, Cole-Parmer Instrument Co., and Research Cartridge, no. 1506–30, Cole-Parmer Instrument Co.) to remove metal ions. The distilled water was prepared by distilling deionized water, using a Corning Model AG3 still. The weak base deionized water was prepared in the Restoration Workshop by the Culligan system described in the introduction (Figure 1). The cation resin was Cullex resin CH-1. The anion resin CW-2 was supplied by the Culligan Company. The calcium carbonate chips were pea-sized crushed marble also supplied by Culligan as Cullnu filter medium and described by them as containing 98.3% CaCO3, 0.5% MgCO3, and 0.03% Fe2O3, and 0.001% CuO.

2.2 Sample Preparation

THE TWO PAPERS chosen for these different waters were:

1) Champion Foldur Kraft, a bleached southern kraft paper containing rosin size and fillers from a single roll of known composition, and, 2) newsprint from cut sheets. Table I shows the paper samples selected for the tests. The five different types of water used for experimental washing of these papers were: 1) laboratory-quality deionized water—LQDI, 2) laboratory quality distilled water—distilled, 3) weakbase deionized water—WBDI, 4) weak-base deionized water passed through calcium carbonate chips—WBDI-Ca, 5) weak-base deionized water passed through calcium carbonate chips and heated to 40�C—WBDI-Ca at 40�C, and 6) Washington tap water—WT at 40�C.

TABLE I PAPER SAMPLES SELECTED FOR THE TESTS

Ten 8″ � 10″ pieces of Foldur Kraft and ten sheets of newsprint were used for each washing procedure. Papers were prewet with a 1:1 solution of denatured alcohol and distilled water, then put immediately into the wash water. Washing consisted of immersing the sample set of 10 sheets in each test water and leaving them immersed for either one, two or three hours. In the standard procedure the paper was held between diamond-shaped, open mesh rubber matting for support, and these “sandwiches” were stacked in a polypropylene tray. Water entered the tray from one side through a diffusion tube which distributed it equally across the tray, passed through the stack of sheets, and flowed out the lower lip of the tray at the opposite side. The sheets were at all times surrounded by moving water. The water flowed through the stack of paper at 0.4 to 1 liters/min.

A variation of this procedure was used for the samples washed in WBDI water. We did not want the water to pass through the copper pipes and had no other way to get flowing water to the washing sinks. Still baths of water, drawn from the Culligan system before the calcium tank, were substituted for circulating baths in the treatments involving WBDI water. The water in these baths were changed every 10 minutes.

For each paper, both Foldur Kraft and newsprint, there were 18 washed sample sets and one unwashed set. The air dried samples were subjected to accelerated aging in both humid (90�C/50% r.h.) and dry (100�C) circulating air ovens for one, two, three, and five weeks. At regular seven-day intervals one sheet from each sample set was removed and tested for folding endurance and brightness.

2.3 Tests

THE PAPER was tested to determine folding endurance, brightness, pH, and total acidity and was analyzed for iron, copper, and calcium.

1. The M. I. T. folding endurance test was run at 1/2 kg load in machine direction only, according to TAPPI T511 su-69.
2. The brightness test was run according to TAPPI T452m-58, using a Photovolt model 670 meter.
3. A titanium punch was used to cut 2.8 mm diameter samples from the papers for metal analysis. The samples were weighed using a Perkin-Elmer model AD-2 electronic microbalance. The iron, copper, and calcium contents were determined using a Varian techtron AA-6 spectrophotometer, with a model 90 carbon rod atomizer and potentiometer A-25 recorder.9
4. pH was measured using the procedure of Kelly10, page 103, Pulp pH Procedure.