JAIC 1989, Volume 28, Number 2, Article 3 (pp. 79 to 96)
JAIC online
Journal of the American Institute for Conservation
JAIC 1989, Volume 28, Number 2, Article 3 (pp. 79 to 96)


Elizabeth Estabrook


3.1 Sample Preparation

COTTON DUCK NO. 10 (11 17 threads/cm2, 0.49 grams/cm2) was cut into 1″ 6″ strips. Three samples were cut for each experimental condition and eraser type. They were then placed in a controlled environment of 21 C and 40% relative humidity for two days. Forty-five strips were kept in the conditioning room for the duration of the experiment. These represent the unaged samples A. The others were artificially aged in a dry oven at 100 C 5 C for seven days. The oven used was a Stabil-Therm gravity oven (Model OV-8, OV-12) manufactured by Blue M Electric Company.

After one week, the samples were removed from the oven and treated with the erasers. The A samples, except three control strips, were also treated. A fabric piece was laid on a sheet of mylar. The eraser was rubbed down the length of the sample five times.25 (Absorene was handled first in order to shape it into a wedge form.) Half of the samples were vacuumed in order to remove the eraser crumbs. The brush head of the vacuum was passed over each sample three times in the same direction as the eraser procedure. The brush head itself was vacuumed between the vacuuming of each sample. A new sheet of mylar was used for each eraser so as not to contaminate the strips. Forty-five of these were placed in the conditioning room. These were labeled B. The rest were returned to the oven for further aging. After seven days, 45 samples, C, were removed. After 14 days, the D samples were removed, and after 21 days, the E samples were removed. All samples were kept in the calibrating room when not in the oven or being examined.

3.2 Visual Examination

All the samples were examined under a binocular microscope (between 7x and 30x magnification) to assess the tenacity and quantity of crumbs as well as the abrasive quality of the eraser.

3.3 Photomicrography

Photomicrographs were taken to record the eraser residue on the fabric and any resulting surface abrasion. These were taken using a Nikon Labophot-Pol microscope with a HFM Automatic microflex and FX-35A camera back. Photomicrographs were taken at a magnification of 40x in both normal and raking light as provided by two tensor lights. The film used was Kodak Ektachrome Tungsten, ASA 160.

3.4 Surface pH and Cold Extraction pH Measurements

Surface pH of the treated and untreated cotton samples was measured using a Fisher Acumet pH Meter, model 830, and a flat surface polymer-body combination electrode 13-639-83 with Ag/AgCl reference. The pH meter was calibrated with buffer solutions of pH 7.0 and pH 4.0, in that order, before each use.26 A droplet of distilled water (pH 5.84–pH 6.84) was placed on the sample. After one minute, the electrode was placed on the droplet. A reading was taken after four minutes. The electrode was rinsed in distilled water for one minute and wiped with Kimwipes between each reading.27

Surface pH measurements were also made on the erasers. A droplet of water (pH 6.98) was placed on the eraser and allowed to stand for one minute before placing the electrode in contact with the eraser. The reading was taken after the two had been in contact for four minutes. Three readings were taken of each eraser.

Cold extraction pH measurements were made of the erasers following the method suggested in TAPPI Standard T509 su-68. The pH of distilled water fell between 6.2 and 7.3 as needed. The electrode was calibrated with pH 4 buffer solution followed by pH 7 solution. Each eraser was grated. Distilled water was added to 1 gram of grounds to bring the volume to 70 ml. The reading was taken after the mixture had been allowed to stand for one hour. Three measurements were taken of each solution.

3.5 Tristimulus Values and Brightness Measurements

Tristimulus values and brightness were measured with a Macbeth 1500/PLUS Quick Key Color Measurement System, which consists of a Color-Eye optical sensor (spectrophotometer), and an IBM personal computer and Quick Key software. The parameters chosen for the measurements were as follows: CIELAB color formula; 2 degree observer; north sky daylight as both primary and secondary illuminants; reflection color-eye mode; ultraviolet energy included; spectral component excluded.28 Three measurements were made and averaged for each data point.29

These measurements are most frequently made on surfaces that are a great deal more uniform than woven textiles. In order to verify that the results obtained were not simply due to the angle at which the textile had been placed in the instrument, a series of readings were taken of sample 1OA: five measurements were made with the sample in the horizontal direction, five in the vertical direction, and five diagonally.

Copyright 1989 American Institute for Conservation of Historic and Artistic Works