PPC Chapter 1 - Fiber Identification

BP Chapter 1 - Fiber Identification

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Book & Paper Conservation Catalog

1. Fiber Identification

Date: 1994

Compiler: Debora Mayer TABLE OF CONTENTS:

1.1. Purpose

1.2. Factors to Consider 1.3 Materials and Equipment 1.4 Treatment Variations 1.5 Bibliography

(see also AIC/BPG/PCC 4. Support Problems 4.4.1)

Fiber identification generally involves taking samples from the artifact and viewing them at 100 times or greater magnification to study the fiber morphology. Stains are often employed to accentuate features and to determine pulping processes. Fiber identification, especially in the case of samples from paper, is not necessarily straightforward. Consultation and study using reference material and known fiber samples is essential.

1.1 Purpose

Identification of the fiber content of the artifact may aid in dating the artifact determining the provenance of the artifact understanding the artist's technique, and, finally, in the selection of conservation treatment procedures and techniques.

The introduction and usage of some fibers and manufacturing process are known. Therefore, it is possible, at times, to date (post) the manufacture of the artifact. Specific fibers and types of paper are sometimes more commonly utilized in certain countries or regions assisting in establishing the provenance of the artifact. Sensitivity to an artist's work and understanding visual qualities of the work can often be enhanced by knowledge of the fiber content and manufacturing process. Different fibers have different chemical and physical properties, including, but not limited to: lignin content, color, absorbency and dimension. Knowledge of the properties may help in predicting how a paper will react to specific treatments (for example: wetting, bleaching, deacidification).

1.2 Factors to Consider

1.2.5 Fiber Classifications

see Cote 1980 for Fiber Nomenclature)

A. Plant Fibers

1. Wood Fibers

a. Gymnosperm (non flowering)

conifers most important group, they are generally evergreen and called “softwood” by tradespeople [examples: pine, spruce, hemlock]

cell types: longitudinal tracheids (fibers), parenchyma

architecture: bordered pits and ray crossfield pitting on tracheids

b. Angiosperm (flowering)

both monocotyledon and dicotyledon trees can be evergreen or deciduous, called “hardwood” by tradespeople [examples: oak, maple, poplar, red and black gum]

cell types: tracheids, vessels, parenchyma, vasi-centric tracheids

architecture: simple and scaliform perforation plates, spiral thickening and pitting patterns on vessels

2. Fruit Fibers

cotton: seed hair from cotton boll, lint (long), linters, (short) coir: hairs from husk of coconut palm

kapok: hairs from pod of kapok tree

cell types: fibers

architecture: cotton: collapsed lumen, convolutions

3. Bast Fibers

comes from inner bark - phloem

trees and shrubs: kozo, mitsumata, gampi

herbaceous dicotyledons: flax, hemp, ramie, sunn, jute, kenaf

cell types: fibers, sometimes shive, parenchyma at times; associated cells generally not found when primary source is

from textile

architecture: type and frequency of nodes and crossmarking on fibers, lumen and fiber width, fiber contour

4. Monocot Leaf Fibers

vascular bundles from xylem

[examples: abaca or manila hemp, sisal, pineapple, New Zealand flax]

cell types: fibers, sometimes vessel segments, epidermal and parenchyma cells

architecture: lumen and fiber width, fiber contour, sometimes fine crossmarkings on fiber, sometimes lumen contains

granular material 5. Grass/Stem Fibers

monocots

plant pulped for fiber or used whole for ethnographic artifacts

[examples: cereal straws (wheat, rice, oat, rye, barley) sugar cane bagasse, cornstalk, bamboo, esparto, rush]

cell types: fibers, vascular bundles, sclerenchyma bundles, serrated epidermal cells, parenchyma, vessels, stomate

(trichomes in esparto)

architecture: dimension of fibers, vessels and associated cells; pitting on vessels, annular thickening on vessels; shape of

trichomes

B. Animal Fibers

Animal fibers are not pulped to form paper, however animal fibers can be found as inclusions in paper. Colored fibers may be from wool. Usually these fibers are intentional additions to the pulp, often from textile sources.

1. Hair protein

[examples:wool, mohair, cashmere]

cell type: fiber

architecture: shape of medulla, cross sectional shape, scale pattern, all can vary from root to tip within same animal

2. Secretions protein

[examples: silk, Bombyx Mori (cultivated), Tussah silk (wild)]

cell type: fiber

architecture: smooth or slightly striated fibers, no skin or outer covering, triangular or wedge- shaped cross-sectional

shape

C. Man Made Fibers

These fibers are not generally found in paper except in small percentages on modern specialty papers. Synthetic fibers however, are used extensively in conservation treatment and storage materials.

1. Cellulose-based

[examples: viscose rayon, acetates] 2. Synthetic fiber

[examples: nylon, polyester, acrylic]

architecture: long fibers, smooth profile without scales or convolutions, may have striations, generally identified

by stains, interference colors and cross sectional shape

D. Mineral Fibers

Rarely found in paper. Strathmore made a watercolor paper in the 1970s with a small percentage of fiberglass. [examples: asbestos, glass]

1.2.6 Optic Properties of Fibers 1.2.7 Wood Fiber Pulping Processes

A. Mechanical

B. Semi Chemical And Semi Mechanical C. Soda

D. Sulfite E. Sulfate (Kraft)

1.3 Materials and Equipment

A. Microscope Slides and Coverslips; Microscope Slide Boxes B. Teasing Tools C. Water D. Stains E. Mounting Media F. Marking Pens G. Reference Samples 1.3.2 Equipment

A. Microscopes

1. Stereo binocular microscope or other magnification 3–10x 2. Bright-field light microscope and accessories

B. Sectioning Equipment

1.4 Treatment Variations

(see AIC/BPG/PCC Spot Tests 10.4.1 and 10.4.2, 1990)

A. Dispersed Fiber Sample (Directly from Object)

Basic steps: (done with the aid of magnification, usually 5–25x)

The artifact is thoroughly examined. Initial observations about fiber content are made. (Example: paper appears homogeneous or heterogeneous, colored fibers present or not, fiber clumps or shive present).

A sample location on the artifact is selected after careful consideration of possible sites. Generally samples are taken from the verso and near the edge of the artifact. There are numerous considerations which determine the most appropriate sample locations.

The sample site is often dampened (if previous testing has shown staining will not occur) with deionized or distilled water applied with a small brush.

A fine stainless steel tweezers or needle can be used to pull individual fibers out of the paper. The fibers are carefully transferred to a microscope slide prepared with a drop of water.

Tools must be clean and inert.

The sample site is placed under blotter and weight as necessary to minimize injury caused by sampling.

The fiber sample, now on the microscope slide, is teased apart with needles or probes in order to separate the sample into individual fibers to the extent possible. Placing the microscope slide on top of a dark background can help visualize the degree of separation.

Let the drop of water on the microscope slide evaporate prior to the application of stain, reagent or mounting media. Low heat, warming tray or room temperature all work well. Protect sample from contamination during drying process.

B. Fiber Staining

A standard fiber staining technique is to apply a few drops of the stain solution to the dispersed fiber sample on a glass microscope slide. Place a coverslip over the sample, lowering it at an angle to avoid creating air bubbles. Allow the slide to stand 1–2 minutes then drain off excess liquid, preferably by tilting the long edge of the slide into contact with a blotter or paper towel.

C. Slide Labelling D. Permanent Mounts E. Reference Collection

F. Disintegration of Difficult Fiber Samples G. Cross Sectioning

Cross sectioning can provide useful information for the identification of many fibers. Often it is not a conclusive test but cross sectional shape can provide confirmatory evidence. These techniques are primarily designed for textile and ethnographic materials.

1. Plate Method

This is the quickest and least expensive way to section a sample. Materials:

1) a plate 1" x 3" (25 x 75mm) the same size as a microscope slide but .010–.020" thick (about 0–.5mm) with holes drilled in it. The holes are .035–0.40" in diameter (about 0.75 mm) made with a No. 65 or No. 60 drill respectively.

2) needle threader or thread 3) new single edge razor blades

Note: the plate can be made of smooth shim brass or plastic. Thinner plates have difficulty in holding the fiber plug and thicker plates interfere with the transmission of light. With regard to hole size, small holes are difficult to thread and large holes tend to lose the fiber slice.

Procedure: Pull a tuft of fibers through the hole in the plate with either a loop of thread (of known identity such as wire filaments, sewing thread, polyester thread, etc.) or with a needle threader. The tuft of fibers must be tightly jammed in the hole to insure that it remains after the top and bottom have been sliced off. If the tuft can be easily pulled through the hole than the finished slice will fall out easily. If the plug is too large the thread or needle threader will break.

The tufts on each side of the plate are cut as flush as possible with a new single edge razor blade. It works well to cut the side with the needle threader first.

Contrast of the fiber cross sectional shape can be enhanced by use of fluids between the sample and the coverslip. The background of light, bright fibers can be darkened by using a drop of liquid with a low refractive index such as n-decane (1.41) or dibutylphtalate (1.49). Dark, dull fibers will appear black against a light background if a liquid of high refractive index, such as bromonaphthalene (1.66) is used.

2. Thin Cross Sections

This method requires the use of a mechanical microtome - either rocking, rotary or sliding type. Basically, the microtome cuts sections 1 micron or greater in thickness. The individual sections are the transferred to a microscope slide for viewing.

3. Other methods include hardy microtome, and grinding embedded samples. 1.4.2 Selected Stains Reagents

A. Safranin-O

0.1% Safranin-O in water

Various formulations, some use 50% ethanol

This is a non-specific plant stain used to enhance fiber morphology. All plant parts stain red to pink. It can be used to make permanent slide mounts.

B.Toludine B

0.1% aqueous solution

This is general stain for woody tissue. Primary cell walls stain purple and secondary walls blue to blue-green. It can be used to make permanent slide mounts.

C. Graff-C-Stain

Integrated Paper Services, 101 West Edison Avenue, Suite 250 P.O. Box 446, Appleton, WI 54912–0446

One of the most common all purpose stains used by paper fiber microscopists. A dispersed fiber sample is stained and the color reaction is observed with transmitted light.

Yellow indicates high lignin content. This typically includes mechanical or semi-mechanical wood pulp and jute fibers. Raw grass, leaf or shive fibers can also stain yellow. Partly purified wood, straw, grass or jute fibers stain less yellow and show greenish, orangeish, or brownish colors. A color shifty from yellow to green to blue to red is an indication of the degree of

processing and reduction in the lignin content of the fiber of the pulp. Blue indicates well purified pulp. This can include wood, grass and leaf fibers.

Red indicates absence of lignin. This inherently includes cotton and the bast fibers (except jute): flax, hemp, ramie, kozo and also includes: high alpha celluloses and highly bleached leaf fibers (manila hemp or abaca).

The stain cannot be used to make permanent slide mounts.

(see AIC/BPG/PCC 10. Spot tests p. 14–16)

D. Herzberg Stain

(see AIC/BPG/PCC 10. p. 16–17)

E. Azo Stain (Yorsten and Green Stain)

Institute of Science and Technology, 500 10th Street., NW Atlanta, GA 30318-5794

Specific stain to confirm unbleached sulfite fibers. Unbleached sulfite fibers stain red or pink while all other fibers stain clear or colorless.

F. 17.5% NaOH

Used to distinguish between mitsumata and gampi fibers. (see AIC/BPG/PCC 10. p. 17)

G. Dupont Fiber Stain #4

Pylam Products Co., Inc., 1001 Stewart Avenue, Garden City, NY 11530

This stain is specifically intended to be used for the identification of synthetic fibers. It is most useful for the identification of nylon, rayon and cellulose acetate.

Boil large sample in a beaker or in a test tube on a hot plate for a few minutes. Withdraw sample and rinse with water. Observe color reaction with reflected light. This procedure is designed for large sample size but the technique can be adjusted, with experience, to use on a micro scale. Place sample on microscope slide. Drop stain onto a sample forming a puddle around the fiber. A ratio of twenty parts stain to fiber is recommended. Heat the slide (and sample) on a hot plate. Rinse sample with water using a pipette to clear stain. Although the stain is intended to be observed with reflected light, the stain can sometimes be observed with transmitted light.

The stain has a long shelf life. Shake stain prior to use to thoroughly re-mix settled out portion. Color reactions:

nylon—red rayon—blue

cellulose acetate—orange

polyester—pale yellow/yellow tan/beige acrylic—beige

olefin—light tan wood/cotton—green glass—doesn't stain

Crosrol, Inc., P.O. Box 6488, Tower Drive, Greenville, SC 29606

Designed to be used directly on textile threads. Color reaction is viewed in normal reflected light without the aid of a microscope. May be able to adjust technique to use on micro sample.

Shirlastain A - for the identification of non-thermoplastic fibers, i.e. cotton, wool and other natural fibers; viscose rayon and other regenerated fibers.

Shirlastain C - for better distinction between natural cellulosic fibers such as cotton, flax, hemp and jute. Shirlastain D - for distinction between cotton and spun viscose rayon.

Shirlastain E - for the identification of thermoplastic fibers (nylon, cellulose acetate, etc.) 1.4.3 Analysis of Fiber Mixtures

A. Counts B. Weight Factors

1.4.4 Other Tests

A. Drying/Twist Test for Bast Fibers

The direction fibers twist upon drying is sometimes used in the identification of fibers, particularly to differentiate between flax and hemp in the textile industry.

Materials: water, hot plate, tweezers

Procedure: Ultimate fibers or thin fiber bundles 5–8 cm in length are immersed in warm water for a few minutes. A fiber is withdrawn and one end held in place on a hot plate (low) and the other free end is directed towards the observer. Direction of twist upon drying is observed. A dark background is helpful.

Results: Flax and ramie twist clockwise. Hemp and jute twist counterclockwise.

B. Scale Casts With Clear Nail Polish

Often it is difficult to see the scale pattern on animal hair fibers, especially those that are dyed dark, densely pigmented, or those that have a wide medulla.

Materials: clear nail polish (Hard as Nails, Strong Nails, etc.)

Procedure: A thin layer of the clear nail polish is brushed evenly over a microscope slide. Let the slide dry slightly. Place the fiber on the coated side and allow to dry thoroughly. If possible, weight down the fiber(s) as they are drying. When the slide has been allowed to dry the fiber(s) can be removed an the slide examined under the microscope with transmitted light. Other methods include 3% gelatin solution in water and cellulose acetate photographic film base softened with acetone. The procedure is most easily performed with a fiber length of 1 inch or greater and it is primarily designed for textile or

ethnographic artifacts.

1.5 Bibliography

Appleyard, H. M. Guide to the Identification of Animal Fibers. Wira, Leeds, UK, 1960, 1978.

Catling, Dorothy and John Grayson. Identification of Vegetable Fibres. London: Chapman and Hall, 1982.

the Institute of Paper Conservation 3 (1978): 51–79.

Collings, Thomas and Derek Milner. “The Identification of Non-Wood Paper-Making Fibres: Part 2,” The Paper Conservator, Journal of the Institute of Paper Conservation 4 (1979): 10–19.

Collings, Thomas and Derek Milner.. “The Identification of Non-Wood Paper-Making Fibres,” The Paper Conservator, Journal of the Institute of Paper Conservation 7 (1982/3): 24–27.

Collings, Thomas and Derek Milner.. “The Nature and Identification of Cotton Paper-Making Fibers in Paper,” The Paper Conservator, Journal of the Institute of Paper Conservation 8 (1984): 59–71.

Cote, W. A. et al. Papermaking Fibers, A Photomicrographic Atlas. Syracuse University Press, State University College of Forestry at Syracuse University, 1980.

Florian, Kronkright and Norton. The Conservation of Artifacts Made from Plant Material. Getty Trust, 1990.

Goodway, Martha. “Fiber Identification in Practice,” Journal of the American Institute for Conservation 26, no. 1 (1987): 27–37.

Graff, J. H. Color Atlas for Fiber Identification. Appleton, WI: Institute of Paper Chemistry, 1940. Isenberg, I. H. Pulp and Paper Microscopy. Appleton, WI: Institute of Paper Chemistry, 1967.

Mauersberger, Herbert R. ed. Matthew's Textile Fibers - Their Physical, Microscopical, and Chemical Properties. 5th ed., New York: John Wiley & Sons, 1947.

Menzi and Bigler. “Identification of Bast Fibers,” Ciba Review no. 123, 33–35.

Parham, R. A. and R. L. Gray. The Practical Identification of Woody Pulp Fibers. TAPPI Press, 1962.

Parham, R. A. and H. M. Kaustinen. Papermaking Materials. An Atlas of Electron Micrographs. Appleton, WI: Institute of Paper Chemistry, 1974.

Schaffer, E. “Fiber Identification in Ethnological Textile Artifacts,” Studies in Conservation 23, no. 3 (1981): 571–585. Strelis, I. and R. W. Kennedy. Identification of North American Commercial Pulpwoods and Pulp Fibers. Toronto: University of Toronto Press, 1967.

Technical Association of the Pulp and Paper Industry, Atlanta, GA. T401: Fiber Analysis of Paper and Paperboard. Textile Institute, Manchester. Identification of Textile Materials. 7th ed., Manchester, 1985.

Tullis Russel & Co. Papermaking Fibres. Scotland: Markinch Fife, 1950. 1.5.3 General Microscopy

Delly, John Gustav. Photography through the Microscope. Rochester, 1980, 1988.

McCrone, Walter; McCrone, Lucy and John Gustav Delly. Polarized Light Microscopy. Ann Arbor, 1978.

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