TSG Chapter VI. Treatment of Textiles - Section J. Compensation for Loss

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Contributors: Originally drafted by Susan Anne Mathisen. Contributions from: Alicia Bjornson, Lucy Commoner, Jennifer Cruise, Patricia Ewer, Martha Winslow Grimm, Jessica Hack, Robin Hanson, Jane Hutchins, Marlene Jaffe, Rebecca Johnson Dibb, Mary Kaldany, Theresa Knutson, Susan Mathieson, Jane Merritt, Denise Migdail, Meredith Montague, Rachael Parr, Zoe Perkins, Nancy Pollak, LoErna Simpson, Deborah Trupin, Jan Vuori.
Editors: Kathy Francis, Jane Lynn Merritt, Nancy Pollak, Deborah Trupin

Copyright: 2020. The Textile Wiki pages are a publication of the Textile Specialty Group of the American Institute for Conservation of Historic and Artistic Works.
The Textile Wiki pages are published for the members of the Textile Specialty Group. Publication does not endorse or recommend any treatments, methods, or techniques described herein.

THIS ENTRY IS A DRAFT

Dyeing of Repair Fabrics and Yarns

Introduction

Fabrics and yarns used in repair or mounting are often custom-dyed to a specific shade to compliment the present condition of the textile or to achieve an overall impression of the original intent of the fabric. Dyes are never applied directly to the surface of the treated object.

Note: It is possible to hand paint a compensation fabric with various media including fabric paints, acrylic paints and permanent inks. These materials can be used to match printed fabrics, aging, dirt and wear patterns which are not easily matched with dyeing. When using these materials it is important to follow proper instructions for setting colors (see TSG Catalogue Chapter 9, Compensation for loss: Painting fabrics).

Factors to consider when dyeing for conservation

Lightfastness

Lightfastness is the extent to which a dye withstands exposure to light, which depends on the kind of chromophore in the dye and its reaction with the energy emitted from the light source. Dyes used for conservation purposes should have maximum fastness to light. The aim is to match the existing color of the faded textile using synthetic dyes which, themselves will not change rapidly with exposure to light. The lightfastness of individual dyes are listed in the Colour Index, (A comprehensive reference on dyes and coloring materials first published by the Society of Dyers and Colorists of England in 1924 and later published jointly with the American Association of Textile Chemists and Colorists. Detailed information is given on tens of thousands of dyes, pigments and other coloring materials as well as various dyeing assistants.) This system uses a scale between 1 and 8, with 8 as the highest degree of fastness. Dyes used for conservation purposes should have a rating of at least 5-6.

Wetfastness

Wetfastness is the extent to which a dye withstands a variety of aqueous solutions, which depends on its chemical and physical bonds with the fiber and how well those bonds can withstand wet treatments. Dyed fabrics exhibit different levels of stability in contact with a variety of aqueous solutions. A dye that is fast in water may not be fast in other aqueous solutions. A dye should withstand exposure to or immersion in water or other aqueous solvents without color loss or bleeding. It is possible for a fabric to retain its original color intensity, but still "bleed" into a wet bath and thus cause staining.

Washfastness

Washfastness is the extent to which a dye withstands a variety of cleaning solutions, which depends on its chemical and physical bonds with the fiber and how well those bonds can withstand cleaning treatments, including drycleaning and spot removal. Dyes used for conservation purposes should also have maximum fastness to washing in common wet cleaning agents such as Orvus WA paste and Igepal. The washfastness of individual dyes is also listed in the Colour Index, on a scale of 1 5, with 5 rated the highest degree of fastness.

Crockfastness

Crockfastness is the extent to which a dye resists color transfer from the surface of a textile to other surfaces by rubbing (crocking).

Note: The above conditions are dependent on completing the dyeing cycle. If a substrate is pulled too early (i.e. judging the appropriate depth of shade visually) fastness properties may be compromised.

Color range and color mixing

This refers to the production of a wide range of colors by the combination of dyes from a basic inventory. When mixing dyes, it is important that the individual dyes have similar (i.e. good) lightfast properties. When dyes of different lightfastness are used, the color will eventually alter towards the hue with the greater lightfastness. Primary colors are preferred when mixing colors, because other available colors are already a mixture, and their base colors and percentages are unknown, making reproducible results harder to achieve. No more than 3-4 dyes should be mixed together to produce a desired color. Retain samples of the dyed fabric with exact dye recipes for future reference.

Note: Manufacturers may modify dyestuff chemistries, as indicated by a name change, or a color may be discontinued. New colors must be re-dyed and compared to the original color sample to identify discernible color differences.

Metamerism

Metamerism refers to the condition in which two different colors or color mixtures appear to be the same under one type of illumination, but differ when viewed under a different type of illumination. To insure a satisfactory color match, compare the compensating fabric to the artifact under the light source with which it will be displayed.

Effects on the fiber

The proper selection of dye and dyeing conditions, including pH, temperature, dyeing time, and agitation can limit harm to the fiber.

Ease of application and safety

The dyeing process should be reproducible, and be able to be carried out safely using equipment and facilities commonly available in conservation labs.

Dyeing small samples

To achieve a desired color, potential dye formulas are selected based on known samples or formulas. Using these formulas, a series of working recipes are made in which the proportions of the component dye colors are varied slightly. Small samples based on the weight of the required fabric or yarn are dyed with each of the working formulas and the color sample is compared to the target color. The procedure is repeated, adjusting the formula until the target color is achieved on the sample.

Dye Record

All dye formulas, as well as samples of undyed and dyed materials, should be retained for future reference. It is very important that the formulas include all chemicals, concentrations, type of water, and dye bath temperatures and durations. Accurate measurements and recording of the recipes are critical for achieving reproducible results.

Dye selection

One dye cannot be used for all fiber types because of the physical and molecular differences in the fibers. The fact that different fibers do not react the same way to a dyestuff can sometimes be an advantage. For example, when a wool/polyester blend is dyed, the two fibers take the dye up differently creating an uneven color. Very often this matches the rather uneven appearance of old, worn fabrics better than a solid color.

Preparation of substrate

Scouring

Before dyeing, the substrate must be scoured to remove any impurities, finishes, or soil. These impurities can provide additional bonding surfaces for the dyes or they can prevent the dye from bonding to the fiber. A typical scouring procedure is:

1. Heat water to 50˚C
2. Add a non-ionic surfactant and stir to dissolve.
3. Add substrate and let sit for 10 to 30 minutes, stirring occasionally.
4. Rinse thoroughly.
5. Let dry.

Note: different fabrics will require different scouring times, temperatures, and detergents, due to fiber characteristics and the extent of processing.

Weighing the substrate

Determine the total weight of the dry substrate.

Prepare the substrate for dyeing

• Yarns should be skeined to avoid tangling and knotting. The skein is tied loosely at both ends and secured with a figure eight. Tied too tightly, uneven dye penetration may result. For tying, use a yarn of a different fiber that will not react with the dye and can be easily found. Hair silk should be braided before dyeing.
• To expose maximum surface area, fabric to be dyed should not be twisted or bunched in the dyebath. Fold lines and stitches in fabric can result in uneven dye penetration.
• Crepeline or net can be folded and stitched, or encased in a net bag.

The dyebath

The dyebath formulation

The composition of the dyebath is based on the dry weight of fabric (on weight of fabric, owf), and each component is expressed as a percentage of this weight. The dyebath consists of:

Water, which is the application medium.
Dye, which has been pre dissolved in water.
Additives, which are dye specific, help to maintain pH, or assist in leveling.

Note: leveling is the even penetration of dyestuffs into the substrate achieved through additives and agitation.

Equipment

Dyepot (glass, enamel, or stainless steel); this should be reserved for dye use.
Thermometer
Heat source (hot plate, stove, dye machine)
Glassware (pipettes and cylinders) for measuring. Use glassware with the smallest gradations. Volumetric flasks should be used for making up dye stock solutions. Pipettes with white markings are easier to read when measuring out dark dye solutions.
Scale
Fume extraction
Safety apparel (mask, gloves, goggles, apron or lab coat)

Water

Volume of water: To insure even distribution of dye as it exhausts, a volume of water sufficient to completely immerse the substrate and allow it to move freely is necessary. Too much water will slow the exhaustion rate and result in a less saturated depth of shade. Each dye will have a specific water volume, calculated from the owf , listed with each recipe.
Water quality: Deionized, distilled, or purified water is recommended. Tap water should not be used because of its impurities and ions, which may affect the dyeing process. Impurities may be overcome with the addition of a sequestering agent. A commonly used agent is hetamexaphosphate, the main ingredient in Calgon water softener.

Dye liquor ratio

The dye liquor ratio is a ratio of the weight of the water to the weight of the fiber. For example, a 20:1 ratio would mean that for every one gram of fiber, there would be 20 grams (or ml) of water. For results to be reproducible, these ratios must remain constant. The evaporation of water during the dye process affects the liquor ratio. Cover the pot to limit evaporation. Add water that is the same temperature as the dye bath. Mark the original depth of the dye bath with a rubber band on a glass rod. Periodically check the depth and replenish the water as necessary. Where heat is needed during the process, maintaining the liquor ratio is less important. With reactive dyes the liquor ratio is very important.

The dye

Stock solutions: A specific weight of dye powder is dissolved in a specific volume of water. The ratio of dye powder to volume of water is expressed as a percentage, and this percentage is the stock solution concentration. A stock solution ensures that the dye powder is completely and evenly dissolved. Typical concentrations for stock solutions are 0.5% or 1%. They are measured as follows:

1 gram of dye in 100 ml of water = 1%
0.5 gram of dye in 100 ml of water = 0.5%

Notes:

• Measuring dye powders: For maximum reproducibility, dye powders should be measured as accurately as possible. Because dye molecules are different weights, 1 gram of one dye may not be the same volume as 1 gram of another dye. The consistency of the weight is important, not the volume.
• Humidity will affect the weighing procedure. At low relative humidity levels, the dye particles become charged and scatter, making both accuracy and safe handling problematic.
• Care must be taken in using heat to facilitate dissolving powders, because heat can degrade some dye molecules in certain classes.
• Prepare solution a day before dyeing to allow the dye powder to dissolve completely.
• Check the stock solution before using, to make sure that there is no powder deposit on the bottom of the flask. Any powder that remains undissolved will alter the stock solution concentration.
• While stock solutions can be stored (in the dark) for a few days to a few months, be aware that color reproducibility can be affected. Reactive dyes that are stored for too long become ineffective. Solutions should be used within the manufacturer's shelf-life recommendations.

A common method for mixing stock solutions:

1. Wear a mask and gloves.
2. Use a plastic cup to weigh the dye powder.
3. Wipe cup with a damp towel to reduce the static charge, place on scale and tare.
4. Weigh the dye powder in the cup.
5. Slowly add a premeasured volume of water from the volumetric flask to the powder and stir with a glass rod.
6. Carefully pour the dye solution into a volumetric flask.
7. To insure that all the dye powder goes into the flask, rinse the cup with a small stream of water or with several rinses of water.
8. Add water up to the total calculated volume.
9. Wet-wipe work area to clean up scattered dye powder.

Depth of shade (DOS): the color saturation of the dyestock For example:

0.1% DOS: very pale
0.2% DOS: pale
0.5% DOS: light
1.0% DOS: medium
2.0% DOS: dark
4.0% DOS: deep

With most dyes, 4% DOS is the darkest color intensity that can be achieved. The fibers reach their dyeing threshold and cannot absorb more dye.

Percent of color: Dye baths consist of one to four colors. Each color is expressed as a percentage that adds up to the total depth of shade percentage (ie., 0.8% blue, 0.4% red, 0.3% yellow is a 1.5% DOS). These percentages are used to calculate the amount of dyestuff for the bath.

Calculations: The weight of substrate determines the amount of dyes, additives and water. Additives are usually a set percentage, the dyes are not. Additives can also be from stock solutions: in which case their volumes must be accounted for in the total bath volume.

FORMULA: Use the following formula to calculate the amount of dye in the bath.

$\frac{WxP}{C}$ Where W is the weight ( in grams) of the substrate, P is the percentage of dye color or assist to be used, and C is the concentration of the stock solution

The result is the number of milliliters of stock solution of each color needed for the dyebath.

EXAMPLE: 5 grams of fabric to be dyed to 2.75%DOS. A 0.5% conc. stock solution is used for each color

GOAL

1.8% blue
0.2% red
0.75% black

The dye:liquor ratio is 20g :1ml

BLUE:

$\frac{5 x 1.8}{0.5} = 18 ml$ blue dyestock

RED:

$\frac{5 x 0.2}{0.5} = 2 ml$ red dyestock

BLACK:

$\frac{5 x 0.75}{0.5} = 7.5 ml$ black dyestock

Total dyestock to be used: $18 ml +2 ml + 7.5 ml = 27.5 ml$

Total volume of dyebath:

$\frac{20g [water]}{1g [fabric]} = \frac{X ml [water]}{5g [fabric]}, X = 100 ml$

Amount water to be added= total volume dyebath - total volume dyestock - total volume of additives

$100 ml [Dyebath] - 27.5 ml [dyestock] - 0 ml [additives] = 72.5 ml[Water]$

Exhaustion:

Exhaustion refers to the proportion of the dye taken up by the substrate in relation to the original concentration of the dye. The general principle is to exhaust as much of the dye as possible onto the substrate through control of physical factors such as temperature, agitation, and addition of exhausting agents (e.g. sodium sulfate, sodium chloride). . Achieving full exhaustion ensures better reproduction of color. Allowing the substrate to cool in the bath may increase dye exhaustion with some dye classes.

Additives are auxiliary agents that are used at various stages in the dyeing process. Each has a concentration independent of DOS. Amounts used for some are determined by weight of fiber and for others by volume of dye bath. They can be grouped according to function: leveling agents, which ensure even distribution of the dye; exhausting agents, which assist dye uptake by the substrate; wetting agents, which assist in saturation of the substrate; and agents which control pH.

General dyeing procedure:

1. Scour the substrate and let dry.
2. Weigh the substrate.
3. Calculate the amount of dye, additives, and water required.
4. Measure and combine water, dye, and additives according to the specific procedure.
5. Wet out substrate in a separate water container for at least 20 minutes to facilitate even dyeing.
6. Add substrate to dyebath. It is important to keep stirring the substrate for even dye penetration, especially during the fixation or exhaustion phases.
7. Slowly raise the bath temperature.
8. Add any assists at the correct points during the dye procedure. Remove substrate to a second container while adding assists. Stir to distribute evenly in the bath. It is important to keep the substrate wet while it is away from the dye bath.
9. Return substrate to dyebath until exhaustion.
10. When dye cycle is finished, let substrate cool in bath until it reaches room temperature. Do not change temperature too fast, especially with wool, as this will produce felting. To speed cooling down rate, the substrate may be transferred to a succession of cooler water baths.
11. Some dyes require fixation with heat or additives.
12. Rinse substrate, or wash if necessary, to insure removal of unfixed dye.
13. Block as necessary. Let dry.

Individual dyestuffs frequently used in textile conservation

Direct dyes

This is a large class of dyes, most with inherent affinities for cellulosic fibers, allowing them to bind to fibers without a mordant.

Fiber types: cellulosics (cotton, viscose rayon)

• Diazol, available from Pro™ Chemical and Dye
• Solophenyl®, available from Huntsman Corp.

Properties

• Lightfastness: varies greatly depending on the manufacturer. After-treatments exist to improve lightfastness but are inappropriate for conservation. Consult the Colour Index, for notation of fastness.
• Wetfastness: soluble in water. After-treatments exist to improve wetfastness but are inappropriate for conservation. Consult the Colour Index, for notation of fastness.
• Colors: muted relative to the colors of reactive dyes.

Additives: The addition of an electrolyte (sodium chloride or sodium sulfate) is necessary for exhaustion. Albatex® PON is added to promote good penetration and leveling. Recommended amount is 0.1g/liter.

Reactive dyes

These dyes form covalent bonds with substrate fibers, becoming a permanent part of the substrate. Dyeing is a two-step process: exhaustion and fixation. During the exhaustion phase, which is facilitated by the addition of salt, the cellulose and the dye have a negative charge and the salt a positive charge. The covalent bond between fiber and dye does not occur until an alkaline fixative is added, in the fixation phase. During this phase the dye on the surface is no longer able to bond with the fiber, but remains soluble. It is the surface dye that bleeds, requiring through washing to remove the unfixed dye.

Fiber types: Cellulosics, sometimes wool

• Procion (MX, cold type; H or HE, hot type) available from Pro™Chemical and Dye.
• Cibacron® F

Classes:

"HOT TYPES" are a slower reacting dye, needing higher temperatures to react. These dyes are not meant to exhaust, and as a result repeated soapings and rinses are necessary to ensure complete removal so that no bleeding will occur in washing.
"COLD TYPES" are not fast enough for use in conservation.

Properties

• Lightfastness: excellent.
• Wetfastness: good, as long as all unfixed dye is removed during post-dyeing processing.
• Colors: shade range consists of bright colors.

Note: Following exhaustion, reactive dyes require the additional steps of fixation and washing off.

• Sodium sulfate (Glauber's salt): to improve exhaustion and reduce the solubility of the dye.
• Sodium carbonate (soda ash): to improve bonding by raising pH to the alkaline range

Metal complex dyes (pre-metallized acid)

These combine acid dyes with metal ions, to form larger complexes that are more washfast than acid dyes alone.

Fiber types: wool, silk, nylon

• Irgalan, manufactured by Ciba Geigy.

Properties

• Lightfastness: excellent.
• Washfastness: excellent but poor leveling.
• Colors: relatively dull in color.
• Very level dyeing on silk can be obtained with careful control of pH and temperature rise. Poor leveling is the result of a too rapid "strike" of the dye which can happen at certain temperatures. Temperature control as well as even distribution of heat in the dye bath are important.

• Albegal A: To improve leveling, patented surface-active leveling agents, such as Albegal and Albegal A are added to the dyebath to slow down the rate at which the dye bonds with the fiber. Recommended quantity: 0.3-1.5% owf.
• Ammonium Sulfate (NH4)2SO4: To improve exhaustion, ammonium sulfate increases the amount of dye-bonding sites on the substrate. Recommended quantity: wool, 1-4% owf; silk, medium/dark shades 0, pale shades 1-4% owf.
• Sodium sulfate (Glauber's Salt) Na2SO4: To improve leveling, sodium sulfate is added to the dyebath to slow down the rate at which the dye is taken up by the fiber. Recommended quantity: wool, 5-10% owf; silk, med./dark shades 5%, pale shades 0.
• Acetic Acid CH3 COOH: To improve exhaustion, acetic acid is used.
Note: Wool should be worked in the additives for 10-15 minutes before adding the dye to the bath. Wool should also be dyed at the boil (100˚C). Working below the boil compromises fastness properties.

Combination: wool-reactive and 1:2 pre-metallized dyes

Introduced in 1985, Lanaset dyes, manufactured by Ciba Geigy, are a combination of wool reactive and 1:2 pre metallized dyes.

Fiber Type: wool, silk, nylon

Trade names: These dyes are usually sold to the home dyer under the distributor's name.
Properties

• Lightfastness: excellent
• Wetfastness: excellent
• Colors: a wide color range with both bright and dull colors is possible.

• Acetic Acid (56%) to improve exhaustion with minimal fiber damage. 1-4% owf is used to adjust the pH of the dyebath to 4.5-5.0.
• Sodium acetate to improve exhaustion. 2-4% owf, depending on the initial pH, is used to produce a pH of 4.5-5.0.
Note: Together acetic acid and sodium acetate produce a buffer solution which maintains the desired pH range throughout the dyeing
• Glauber's Salt(Na2SO4) to improve leveling. The percent used varies with the depth of shade (DOS). With a DOS of less than 0.5%, use 10% owf. With a DOS of 0.5-1% , use 5% owf. A DOS of 1-2% requires 2.5% Glauber's Salt. Above 2% DOS, no Glauber's Salt is added.
• Albegal SET to improve level dyeing by slowing reaction rate, but can also reduce exhaustion. 1% owf is used.

Commonly encountered problems in dyeing

Uneven application of the dye to the substrate, failure of dyes to exhaust, and failure to obtain desired color may result from:

• Failure to scour substrate properly.
• Substrate not completely wetted before dyeing.
• Improper preparation of the stock solution.
• Too rapid rise in temperature.
• Failure to control pH.
• Substrate not stirred during exhaustion or fixation phases. Gentle movement of the fiber insures even penetration of the dye.
• Assists added at wrong stage or in wrong proportions.. They must be evenly distributed throughout the dyebath before the fiber is placed in the dyepot.

Safety in the dye lab

Toxicity

All dyes and auxiliary chemicals should be handled with caution. Material Safety Data sheets or product information should be consulted for information on specific dye ingredients, handling, and disposal concerns. Health effects of dyeing materials can be both acute (such as immediate irritation to eyes or skin) or chronic (taking years to develop, such as lung disease or cancer).

Powders

Dye powders are highly divided particulates which spread easily and should be handled in a glovebox or fumehood. To protect against inhalation dangers, an appropriate dust mask should be worn. Avoid skin contact with dyes and chemical assists by wearing latex gloves, an apron, and safety goggles. Procion dyes in particular are sensitizers when inhaled or through skin contact, and can lead to the development of allergies.

Disposal

After dyeing, the dyebath can usually be flushed down the drain with a large volume of water. Follow all applicable federal, state and local regulations regarding the disposal of dyes containing heavy metals or other toxic materials.

Other safety tips

• Work in a well-ventilated area.
• Keep artifacts away from dyeing areas.
• Use a glass rod to stir solutions, not a thermometer.
• Do not use a mouth pipette to measure dyes.
• Do not leave a dyepot unattended on a heat source.
• Do not eat or smoke in the dyeing area.
• Label and cover all containers of dye.

Bibliography

AATCC and Society of Dyers and Colourists (Great Britain). The Colour Index. Available by subscription from https://www.colour-index.com

American Association of Textile Chemists and Colorists, pub. 1981. Dyeing Primer, reprint from Textile Chemist and Colorist. Research Triangle Park, NC.

AATCC. Buying Guide to Products and Services for the Textile Wet Processing Industry. Published as the July issue of Textile Chemist and Colorists by the American Association of Textile Chemists and Colorists.

Aspland, J.R. 1991, 1993. A Series on Dyeing. Textile Chemist and Colorist, 23 (11), and 25 (11).

Billmeyer, Fred W. Jr. and Max Saltzman.1966. Principles of Color Technology. New York: Interscience Publishers.

Celikiz, Gultekin and Rolf G. Kuehni, eds. 1983. Color Technology in the Textile Industry. Research Triangle Park, NC: AATCC.

Crowder, Jennie and Sally Vinroot. 1981. The New Dyer. Loveland, CO: Interweave Press, Inc.

Duff, David G. and Roy S. Sinclair. 1989. Gile's Laboratory Course in Dyeing. Fourth Edition. Bradford, England: Society of Dyers and Colourists.

Finch, Karen and Greta Putnam. 1985. The Care and Preservation of Textiles. London: B.T. Batsford.

Flury Lemberg, Mechthild. 1988. Textile Conservation and Research. Bern: Schriften der Abegg Stiftung.

Giles, Charles Hugh. 1974. A Laboratory Course in Dyeing. Bradford, Yorkshire: The Society of Dyers and Colourists.

HunterLab. 1987. The Science and Technology of Appearance Measurement. Reston, VA: Hunter Associates Laboratory, Inc.

Knutson, Linda. 1983. Shades of Wool for Lanaset Dyes. Yakima, WA: Linda Knutson.

Knutson, Linda. 1986. Synthetic Dyes for Natural Fibers. Loveland, CO: Interweave Press.

Landi, Sheila. 1985. The Textile Conservator's Manual. London, Butterworths.

McCann, Michael. 1993. Dyeing Safely, Art Hazard News, 16 (5): 3-6.

Munsell Color. 1976. Munsell Book of Color. Baltimore, MD: Macbeth, a Division of Kollmorgen Corporation.

Rivlin, Joseph. 1992. The Dyeing of Textile Fibers, Theory and Practice. Philadelphia, PA: Philadelphia College of Textiles and Science.

Rossol, Monona. 1990. The Artist's Complete Health and Safety Guide. New York: Adworth Press.

Rossol, Monona. 1985. Protecting Yourself: Fiber Art Hazards and Precautions, Fiberarts12(6): 42-45.

Various. 1980,1987. A Basic Course in Dyeing for Conservation as Carried out at the Textile Conservation Centre. (handout). Based on a paper by Coleen Wilson, 1980. (Also listed as Revised 1987 by Rosanna Zubiata.)

Vuori, J. and S. Tse. 1997. Light Fastness of Irgalan and Lanaset Dyed Silk: Immersion vs Direct Application, Results of a Preliminary Study. ICOM Textile Working Group Newsletter13(1): 12-14. Also reprinted in Textile Conservation Newsletter (33) Fall:14-18.

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