Fabrics for the twenty-first century - The Courtauld Institute of Art

Young and Jardine Fabrics for the twenty-first century
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More sophisticated theoretical models have been
proposed to describe crimp in fibres and yarns,
which take into account yarn diameter and the
angles of the curved elements (Manjit, 2009).
However, these models were not developed for this
research because the measurement of A and λ, resulted
in estimated errors of λ ± 0.002 mm and A ±
0.004 mm, thus the limiting factor in the accuracy of
determining the crimp.
Measurement of drape
The tactile properties of a fabric with which there is a
sensory response is known within the textile industry as
‘hand’ and encapsulates not only physical but also
human perception, physiological, and social factors.
However, there is no direct measurement of hand.
Researchers have attempted to develop different
methods to evaluate hand; these usually involve measuring
many parameters and attempting to correlate them
with human studies (Pan, 2007). Drape, colour, lustre,
and texture are important factors that affect the
aesthetics and kinaesthetics of fabrics. Drape is just
one factor that will influence hand and has been
chosen as the starting point in this research because it
is usually assessed empirically by feeling a fabric and
observing how it hangs under its own weight.
Practically, it affects the canvas or painting handling
properties when stretching, lining, and folding around
a stretcher bar.
The textile and clothing industry use drape to class
and compare batches of fabric. It is described by
BS5058:1973 (British Standards Institute, 1973) as
‘the extent to which a fabric will deform when
it is allowed to hang under its own weight’.
Commercially, measurements are made using the
Cusick drape meter (Cusick, 1965). A drape meter
was constructed based on the 1968 Cusick design
(Cusick, 1968) capable of capturing digital images
from which to calculate the drape coefficient (DC), a
number between a theoretical maximum of 1 (stiff)
and 0 (floppy). Two concentric discs in the middle of
the opaque box hold the annular ring of fabric, allowing
it to drape into folds around the bottom supporting
disc and held in place by the top disc. The
instrument has a supporting disc of 18 cm diameter,
using test samples of 30 cm diameter. A shadow of
the draped fabric is cast down onto the image
window from a point light source above the discs.
The shadow is imaged by a digital camera, and the
area of the shadow the footprint is calculated using
Image J software. The DC is calculated using
DC =
Area under the draped sample − Area of support disk
Area of the sample − Area of support disk
(3)
Studies in Conservation 2012 VOL. 0 NO. 0
The correlation of drape analysis using image processing
techniques with other fabric properties has
been investigated in relation to the apparel industry
(Robson & Long, 2000).
Measurement of lustre
Lustre is a term used to describe the way light is scattered
from a fabric resulting from reflection, refraction,
and diffraction at the yarns. A combination of
macro-level gloss measurement and micro-level
image analysis of yarns has been applied to determine
which parameters influence lustre (Kim et al., 2004).
In the apparel industry, lustre is measured in accordance
with BS3424-28:1995 (British Standards
Institute, 1995) to determine the specular gloss of the
coated fabrics. A modified version of this was
employed on the uncoated fabrics using a Sheen
Instruments Tri-Microgloss 20-60-85 Meter (Model
160) at 60°. Measurements were made in three places
for each warp, weft, and bias direction.
Results
Crimp data
Table 2 and Fig. 2 summarize the measured parameters
A (amplitude) and λ (wavelength) from which crimp
and crimp ratio Cr are calculated. A Cr = 1 means
that the warp and weft have the same crimp in both
directions. P110 2008 has a warp crimp of 0.073, weft
crimp of 0.027, and Cr = 0.37. Polyflax 1008 has a
warp crimp of 0.09, weft crimp of 0.06, and C r =
0.67. Therefore, the Polyflax 1008 has more even
crimp, as does Ulster linen 3151 (Cr = 0.9), 9.1 oz
Clipper (C r = 1.07), and Carbotex 03_82 (C r = 1.23).
The Carbotex 03_82, 9.1 oz Clipper and the Stern
16221 (Cr = 7.42) are the only cases where the crimp
is greater in the weft than the warp.
Drape data
Table 3 and Fig. 3 summarize the drape data for both
the front and back face of the fabrics. Rigid cardboard
that does not drape has been used for comparison
(measured DC = 1). The results demonstrate that
Sailcloth 00169 has very little drape (DC = 0.91
front), whereas Kevlar® Scenic (DC = 0.68 front) is
closest to Ulster linen 3151 (DC = 0.64 front).
Figs. 4A and B show the drape images for Ulster
linen 3151 and Sailcloth 00169. The linen drapes
well whereas the sailcloth drapes less. Some fabrics
exhibit a large difference in their DCs between the
front and back faces, most notably Plastock 33/51
which has values of 0.48 (front) and 0.82 (back),
respectively. Thus, it will conform to a corner or
edge better with the front face uppermost. (This is
the face that would be on the uppermost when
weaving. Usually, fabric is rolled with the back face
on the inside.) There is a small difference for