UNEFM, Maestría en Museología, Nancy kerr ability of textiles

1. JAIC 2000, Volume 39, Number 3, Article 3 (pp. 345 to 353)
ABILITY OF TEXTILE COVERS TO PROTECT ARTIFACTS
FROM ULTRAVIOLET RADIATION
NANCY KERR, LINDA CAPJACK, & ROBERT FEDOSEJEVS
1 INTRODUCTION
Among the many agents that damage museum objects, light is regarded as one of
the most pervasive and harmful. The UV region is noteworthy because many
materials absorb light within this region. The light-absorbing chromophores they
contain often enter into or stimulate undesirable reactions such as photochemical
oxidations and reductions and the cleavage and formation of bonds (Reinert et al.
1994). All organic objects are at risk when exposed to light, including objects made
from textiles, paper, wood, parchment, leather, and feathers. Because the action of
light is cumulative, reducing the illuminance and exposure time and screening out
the most harmful UV rays may slow light damage to objects. For storage areas,
Garry Thomson (1986) suggests that a good UV filter should transmit less than 1%
of the incident radiation between 320 and 380 nm. Fabric covers are sometimes
used to protect objects from UV, visible light, and dust in conservation laboratories
and museums. Black textile covers are used in the textile conservation laboratory at
the Metropolitan Museum of Art. At the Isabella Stewart Gardner Museum in
Boston, decorative textiles cover many glass display cases, and sheer fabrics on the
windows act as light screens. Fabric covers on display cases are moved aside by
visitors when they want to view the objects. In historic homes, textile covers protect
upholstered furniture when visitors are absent. Window blinds and draperies are
used to control the illuminance because window glass filters some but not all UV
radiation between 300 and 400 nm (Thomson 1986).
Although textile covers are routinely used for protection against damage by light,
how well various fabrics screen UV radiation has not been reported in the
conservation literature. The principal research objective of the present study was to
determine how effectively various textiles and tissues typical of those used for this
purpose in a conservation laboratory or museum block the transmission of UV
radiation. A second objective was to measure the fiber, yarn, and fabric
characteristics that contribute to the blocking of UV radiation and to determine the
relative importance of each in that regard.
2 EXPERIMENTAL
2.1 FABRICS

2. A variety of fabrics, both woven and nonwoven, was selected for this study. Most undyed
fabrics were obtained from a commercial source. Woven and knitted fabrics made of 100%
cotton, 65/35 polyester/cotton, 50/50 polyester/cotton, and 87/13 nylon spandex were
purchased locally. Nonwoven textiles included Cerex spunbonded (SB) nylon, Reemay
spunbonded polyester, and Tyvek spunbonded polypropylene. For comparison with the
synthetic nonwovens, an acid-free tissue was also included. Fabrics were tested as received
from the suppliers.
2.2 METHODS
Fabrics were characterized by fiber type, fabric mass, fabric count, thickness, level of
delustering, structure, and cover. Fiber type was confirmed through microscopic analysis
and chemical solubility tests (American Association of Textile Chemists and Colorists
1996). Fabric structure was identified as woven, knitted, or spunbonded. Canadian General
Standards Board test methods (1990) were used to determine fabric weight, the mass per
unit area (g/m2), fabric count (the number of yarns/cm or wales and courses/cm), and fabric
thickness (Custom Scientific thickness tester [CS-55-225], foot of 28.7 mm diameter,
pressure of 1 kPa). Level of delustering was determined qualitatively by examining the
appearance of manufactured fibers under a transmitted-light microscope at 400x and
estimating the relative amount of pigment in specimens by comparison with
photomicrographs in AATCC (1996) Test Method 20–1990 (Fiber Analysis: Qualitative).
Fibers classified as bright (B) had little or no titanium dioxide (TiO2). Semidull fibers (S-
D) were lightly pigmented (approximately 0.3% by weight TiO2) and dull (D) fibers were
highly pigmented (approximately 2% by weight TiO2) (fig. 1). Titanium dioxide is added
as a fine white powder to reduce the shine of manufactured fibers (Saunders 1988).
Fig. 1. Relative amount of TiO2 pigment in fibers (left to right): bright, semidull, and dull (after AATCC
[1996] method 20, figs. 35, 24, and 33, respectively)
2.2.1 Fabric Cover
Fabric cover, defined as the percentage of a given fabric area covered by yarns or fibers,
was determined by image analysis. A microscope with a 4x objective magnified the fabric,
and a video camera resolved the image, which was digitized and then processed by a
computer. The video image consisted of 256 x 256 pixels, each having a value between 0

3. and 255 representing the brightness of that pixel. For each fabric, the illumination was
adjusted such that the peak pixel values, corresponding to open areas in the fabric, had an
average value of approximately 250. A cutoff intensity value of 125 was used to separate
the pixels representing open areas from those representing areas covered by yarns or fibers.
The number of pixels falling above and below this cut-off value was determined and then
the percentage of covered area was calculated. Reported cover percentages are based on the
average of five images per fabric. The choice of an intensity value of 125 to define the edge
of the fibers is based on the assumption that the transmission of light through the fibers
themselves is negligible, which is not always the case. The interlaced structure of the fibers
results in only a fraction of the fibers observed in a given microscope image being in sharp
focus with clearly defined edges. Fibers that are out of focus will have blurred edges,
making it difficult to precisely determine the edge position. Based on these limitations, the
estimated accuracy of the cover measurement was on the order of several percent due to
dependence on the choice of the threshold value separating dark from light pixels.
2.2.2 UV Transmission
UV transmission through fabrics selected for the study was measured on a Varian Cary
2415 UV-Vis-NIR spectrophotometer fitted with an integrating sphere to collect forward-
scattered and transmitted light. The wavelength range recorded was 280–380 nm, and a
monochromator filtered radiation to a 2 nm bandwidth. Fluorescence was eliminated by
means of a 3-mm-thick UG-11 fluorescence-blocking filter adapted for the
spectrophotometer. From each sample, five random specimens were cut. Each woven
specimen had different warp and weft yarns, and each knitted specimen had different
lengthwise ribs and crosswise courses. For the UV transmission measurements, four
specimens of each fabric were glued on washers with a diameter of 5 cm and a circular
opening of 2 cm. The UV transmission was calculated by averaging the measured values
over the range of 280–380 nm. Davis (1995) determined that normally four specimens per
sample must be scanned to ensure that the estimated mean UV transmission of the sample
will have a standard error no greater than 5% of the mean.
ABILITY OF TEXTILE COVERS TO PROTECT ARTIFACTS FROM
ULTRAVIOLET RADIATION
NANCY KERR, LINDA CAPJACK, & ROBERT FEDOSEJEVS
3 RESULTS AND DISCUSSION
When incident radiation contacts a fabric (fig. 2), part of that radiation is scattered from the
surface and the remainder is absorbed by or penetrates through the fabric. A fraction of the
radiation passes through the fibers and spaces between the yarns. The absorbed radiation is
taken up by the chromophores in the fibers as well as by other materials present (dyes,
delustrants, optical brighteners, finishes). A fabric's ability to protect museum objects or
items from ultraviolet light in conservation laboratories, historic houses, storage areas, or
limited-view exhibits can be increased by selecting fibers, dyes, and finishes that have

4. excellent absorption of UV radiation. The effect of a variety of fiber types, fabric
constructions, dye, and pigment on the transmission of UV is reported in table 1. Fabrics 1
to 9 in table 1 vary in fiber content, but all are undyed, plain-weave fabrics made from spun
yarns. It should be noted that the UV transmission values represent the “worst case” or
maximum values because they are obtained by passing UV rays in a direction perpendicular
to the plane of the cloth. Incident light during use may not be perpendicular to the fabric
surface, but may contact it at an angle, thereby increasing the scattering and effective cover.
Table 1. UV Transmission and Characteristics of Fabrics, Spunbonded
Webs, Acid–free Tissue
Fiber Type
Fabric
Descriptiona
Massb
(g/m2)
Fabric
ThicknessbC
(mm)
Coverb
(%)
% UV
Transmissionb
d 280–380 nm
Undyed Plain
Wegve
Fabrics, Spun
Yarns
1. Cotton unbleached 160 0.46 98 6
2. Cotton unbleached 117 0.29 90 7
3. Cotton blsached 106 0.28 93 27
4. Linen blsached 107 0.26 77 19
5. Rayon bright 140 0.33 92 23
6. Wool unbleached 118 0.37 88 16
7. Acrylic semidull 131 0.41 89 15
8. Polyester semidull 133 0.35 90 12
9. Nylon semidull 125 0.36 86 22
Spunbonded
Webs and
Acid-Free
Tissue
10. Cerex
nylon
bright 53 0.14 83 39
11. Reemay
polyester
semidull 45 0.24 82 20
12. Tyvek
polypropylene
dull 42 0.18 98 2
13. Acid-free
tissue
N/A 19 0.05 92 19

5. Dyed Woven
and Knit
Fabrics
14. Print cloth
65/35poly/
cotton
black 91 0.20 92 6.1
15. Cotton
muslin
black 131 0.36 97 1.7
16. Double
knit 50/50
poly/cotton
black 192 0.62 99 1.1
17. Rib knit
cotton
black 234 0.76 98 0.3
18. Stretch
knit 87/13
nylon/spandex
black 210 0.60 99 0.1
a Bright, semidull, and dull refer to amount of the TiO2 delustering agent in manufactured fibers.
b Mass,cover, thickness,and UV transmission, average of five measurements
c Thickness underpressure of lkPa
d Refers to transmission through the yarns and the spaces between
Fig. 2. Process of light transmission through fabric. Radiation incident upon a fabric (Io) is either scattered (Is),
absorbed (IA), transmitted through openings (ITO) or transmitted through the fibers (ITF). The total
transmission (IT) is equal to the sumof ITF and ITO. Transmitted rays through the fibers and openings may
damage the object beneath.
3.1 EFFECT OF FABRIC PARAMETERS ON UV TRANSMISSION
The fiber composition of a fabric affects UV transmission. The poly (ethylene
terephthalate) polyester fabric (#8) listed in table 1 had an average transmission of 12%
over the 280–380 nm range and was a more effective UV blocker than all but the

6. unbleached cotton muslins. Poly (ethylene terephthalate)-type polyester contains phenyl
ester groups that are known to exhibit a very strong UV absorption below 310 nm.
Synthetic fibers spun from aliphatic polymers such as nylon, acrylic, and polypropylene
block little UV radiation unless they are delustered or dyed. The presence of titanium
dioxide delustering pigment in the acrylic, polyester, nylon, Reemay polyester, and Tyvek
polypropylene samples contributed to the blocking of UV radiation by these fabrics.
Titanium dioxide absorbs about 90% of the incident radiation uniformly across the UV
region 280–380 nm (Thomson 1986), and has an absorption maximum at approximately
350 nm (Reinert et al. 1997).
Fabric mass and cover also affect UV transmission. Among the fabrics shown in table 1,
those with the highest mass transmitted the least UV radiation; for example, black fabrics
nos. 16, 17, and 18 transmitted 1.1, 0.3, and 0.1% UV, respectively. Their low transmission
was also a function of their color, thickness, and high cover (98-99%). Other researchers
(Berne and Fischer 1980; Pailthorpe 1993) have also noted that high mass and cover
resulted in low UV transmission values. Davis (1995) found that the relationship between
UV transmission and cover is not as strong as mass. A fabric with high cover does not
necessarily block UV rays effectively because some transmission occurs through the fibers
or yarns as well as the spaces between them; for example, fabric #10, an undelustered
Cerex nonwoven, has a cover of 83% and an open area of 17%. The UV transmission of
this fabric is 39%, showing that UV radiation is not only passing through the open area but
also penetrating the fibers.
3.2 UV TRANSMISSION THROUGH TYPICAL MUSEUM FABRICS
AND ACID-FREE TISSUE
The UV transmission and other physical characteristics of fabrics frequently used as light
and dust covers are presented in table 1, entries 1–3 and 10–15. Cotton is known to be a
weak absorber of UV once the natural pigment is removed by bleaching (Pailthorpe 1993;
Reinert et al. 1997). This observation is consistent with data obtained for UV transmission
by two unbleached muslins (nos. 1 and 2), which, though they differ substantially in mass,
had almost identical transmissions of 6% and 7%, respectively. The much greater (27%)
UV transmission of fabric no. 3, a bleached cotton muslin, even though it has a cover and
mass similar to those of muslin no. 2, is also in agreement with Reinert's suggestion. Figure
3 shows the difference in transmission of UV through bleached, unbleached, and dyed-
black cotton muslin.
Fig. 3. Percent transmission of UV through unbleached cotton muslin, bleached cotton, and black cotton

7. muslin
Cerex nylon spunbonded web (no. 10) is typically used to separate textiles in storage, to
line trays, and to protect items from dust. It provides little protection from UV radiation,
however, transmitting about 40% of the incident radiation. Figure 4 shows the variation in
transmission of UV with wavelength through Cerex and Reemay fabrics, SB polyester, and
acid-free tissue. Other researchers have noted the permeability of aliphatic nylons to UV
radiation over the whole UV region (Reinert et al. 1997).
Fig. 4. Percent transmission of UV through Cerex nylon, Reemay polyester, Tyvek polypropylene, and acid -
free tissue
Among the spunbonded nonwovens made of nylon, polyester, and polypropylene, the most
effective UV screen was the Tyvek SB polypropylene (no. 12), which transmitted 2% of the
UV radiation. This spunbonded nonwoven is a water-resistant, flexible material typical of
the “synthetic paper” that is used in the conservation laboratory as a cover for rolled textiles
in storage, curtains in storage areas, and covers for objects that are undergoing conservation
treatments. The reason Tyvek blocks the transmission of UV radiation so well is its fiber
content, its high cover (98%), and the heavy pigmentation of the fibers.
3.3 DYED FABRICS
Our research (Davis 1995; Davis et al. 1997) and that of many others (Pailthorpe 1993;
Gies et al. 1994; Pailthorpe 1994; Reinert et al. 1997) has shown that fabrics dyed dark
shades or saturated colors rather than pastels are very effective at screening UV radiation.
Five black fabrics are shown in table 1 to illustrate this finding. The black fabric that
transmitted the most UV (6.1%) was a low-mass, thin 65/35 polyester/cotton fabric (no.
14), and yet it blocked as much UV as the most effective UV-blocking fabric in the undyed
group, a heavy unbleached muslin (no. 1). Three of the knitted black fabrics in this group
(nos. 16–18) transmitted only 1% of the UV, thereby meeting Thomson's criterion for an
effective UV filter (Thomson 1986). Their effectiveness is a combination of color as well
as high thickness, mass, and cover, resulting from the knit structure. If black fabrics are
used in a conservation laboratory or museum setting to protect objects from light, they
should first be tested for colorfastness to crocking and water.
4 CONCLUSIONS
If fabric is chosen carefully, textile covers are an inexpensive, reusable, and effective
means of reducing the exposure of museum objects to UV radiation. The fabric

8. characteristics that most influence UV transmission are mass, thickness, and color: the
higher the mass and thickness and darker or more saturated the color, the less UV radiation
transmitted through the fabric. Three fabrics reported in this study met Thomson's (1986)
criterion of blocking 99% UV, a black 50/50 polyester/cotton double knit and a black
stretch knit of 87% nylon and 13% spandex. Tyvek transmits 2% of the UV radiation, but
has the important advantage in the museum context of being both waterproof and much
lighter in weight than either the nylon/spandex or the double knit. The natural pigment in
unbleached cotton muslin makes it a more effective UV screen than bleached cotton.
Spunbonded webs with low cover (Cerex and Reemay) transmit 39% and 20% of the UV,
respectively, and so are not useful covers for light-sensitive objects.
ACKNOWLEDGEMENTS
This research was funded in part by the Endowment Fund for the Future at the University
of Alberta. The Government of Canada Summer Career Placement program also provided
support for two undergraduate students of human ecology. We recognize the significant
contributions of Jennifer Moroskat and Tannis Grant to this research project
REFERENCES
AATCC. 1996. Fiber analysis: Qualitative: Test Method 20–1990. In Technical manual of
the AATCC, vol. 69. Research Triangle Park, N.C.: American Association of the Textile
Chemists and Colorists. 47–62.
Berne, B., and T.Fischer. 1980. Protective effects of various types of clothing against UV
radiation. Acta Dermato-Venereologica60:459–60.
CGSB. 1990. Textile test methods, Can/CGSB-42. Ottawa: Canadian General Standards
Board.
Davis, S.1995. Relationship of fiber type, mass, and cover to the sun protection factor of
fabrics. Master's thesis, University of Alberta, Edmonton, Alberta, Canada.
Davis, S., L.Capjack, N.Kerr, and R.Fedosejevs. 1997. Clothing as protection from
ultraviolet radiation: Which fabric is most effective? International Journal of
Dermatology36:374–79.
Gies, H. P., C. R.Roy, G.Elliott, and W.Zongli. 1994. Ultraviolet radiation protection
factors for clothing. Health Physics67:131–39.
Pailthorpe, M. T.1993. Textile parameters and sun protection factors. In Proceedings of the
Textiles and Sun Protection Conference, ed. M. T. Pailthorpe. Kensington, NSW, Australia:
Society of Dyers and Colorists of Australia and New Zealand. 32–53.
Pailthorpe, M. T.1994. Textiles and sun protection: The current situation. Department of
Textiles Technology, University of New South Wales, Sydney, NSW. 20–21.
Reinert, G., E.Schmidt, and R.Hilfiker. 1994. Facts about the application of UV-absorbers
on textiles. Melliand Textilberichte7–8:E151–E163.

9. Reinert, G., F. Fuso, R.Hilfiker, and E.Schmidt, E.1997. UV-protecting properties of textile
fabrics and their improvement. Textile Chemist and Colorist12:36–43.
Saunders, J. H.1988. Polyamides, fibers. In Encyclopaedia of polymer science and
engineering, ed. J. I.Kroschwitz et al.New York: Wiley. 422.
Thomson, G.1986. The museum environment 2d ed. London: Butterworths.
FURTHER READING
Capjack, L., N.Kerr, S.Davis, R.Fedosejevs, K.Hatch, and N.Markee. 1994. Protection of
humans from ultraviolet radiation through the use of textiles: A review. Family and
Consumer Sciences Research Journal23:198–218.
Hilfiker, R., W.Kaufmann, G.Reinert, and E.Schmidt. 1996. Improving sun protection
factors of fabrics by applying UV-absorbers. Textile Research Journal66:61–70.
SOURCES OF MATERIALS
In Table 1, fabrics that were purchased from
Testfabrics, Inc.
P.O. Box 420
Middlesex, N.J. 08846
are listed here with their style numbers: 3. #400 bleached cotton print cloth; 4. #L-
61 handkerchief linen; 5. #266 spun viscose rayon challis; 6. #530 worsted wool
challis; 7. #981 Spun Creslan acrylic type 31; 9. #361 spun nylon 6,6 Dupont type
200.
Cerex spunbonded nylon by Monsanto
HTC Laboratories
5575 Casgrin Ave.
Montreal, Quebec H2T 1Y1
Canada
Tyvek spunbonded polypropylene Type 1422A
Bury Media and Supplies Ltd.
B-5-4255 Arbutus St.
Vancouver, British Columbia V6J 4R1
Canada
Reemay spunbonded polyester #2014
Carr McLean Ltd.
461 Horner Ave.
Toronto, Ontario M8W 4X2
Canada
AUTHOR INFORMATION

10. NANCY KERR has a B.Sc. in home economics from the University of Guelph, an M.Sc. in
clothing and textiles from the University of California at Davis, and a Ph.D. in fiber and
polymer science from North Carolina State University. She is a professor in the Department
of Human Ecology at the University of Alberta. Her teaching and research focus on textile
science and conservation topics. Current projects include UV transmission through textile
materials, degradation and stabilization of historic textiles, and industrial hemp. Address:
Department of Human Ecology, 302 Human Ecology Building, University of Alberta,
Edmonton, Alberta T6G 2N1, Canada
LINDA CAPJACK received her M.Sc. in clothing and textiles from the University of
Alberta. She is associate chair and associate professor in the Department of Human
Ecology at the University of Alberta. Her research interests include the functional design
process and environmental protective clothing, focusing recently on clothing to protect
from ultraviolet radiation. She has worked collaboratively with Dr. Nancy Kerr and Dr.
Robert Fedosejevs on identifying fabric characteristics that contribute to decreased
transmission of UV. Address as for Kerr
ROBERT FEDOSEJEVS received his B.Sc. and Ph.D. degrees from the University of
Toronto, Canada, in 1973 and 1979. He subsequently was a research associate at the Max
Planck Institute in Germany. He joined the Department of Electrical and Computer
Engineering at the University of Alberta as associate professor in 1982 and currently holds
the position of C. R. James/MPBT/NSERC Senior Industrial Research Chair in the
Application of Laser and Spectroscopic Techniques to the Natural Resources Industry. His
research interests include the study of laser-plasma interactions and the application of laser
and spectroscopic techniques to the characterization of materials. Address: Department of
Electrical and Computing Engineering, 238 Civil/Electrical Engineering Building,
University of Alberta. Edmonton, Alberta T6G 2G7, Canada
Received for review July 25, 1999. Revised manuscript received June 1, 2000. Accepted
for publication May 16, 2000