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Black walnut, Osage orange andeastern
redcedar sawmill waste asnatural dyes: eect
ofaluminum mordant oncolor parameters
Kelsie Doty1*, Sherry Haar2 and Jooyoun Kim2
Introduction
Natural plant dyes and dyeing processes have the potential to impact the triple bot-
tom line of niche markets in both positive and negative ways. e triple bottom line is
a framework to measure environmental, social, and economic impacts on sustainabil-
ity (Elkington 1998). Sustainability is defined as ‘the principle ensuring that our actions
today do not limit the range of economic, social, and environmental options open to
future generations’ (Elkington 1998, p. 20). Sustainably managed harvesting of dyestuffs
provide a renewable, carbon reducing , biodegradable alternative agriculture product
Abstract
The triple bottom line can be impacted in both positive and negative ways by the use
of tree sawmill waste as a natural dye. Trees contain a biomordant in the form of tannin
which may eliminate the need for metallic mordants, thus reducing water, thermal
energy, residual waste, and exposure to a mordant chemical. Dyeing with mill waste
provides an economic option for an existing timber manufacturing byproduct. This
research analyzed the impact of potassium aluminum sulfate (PAS) on dye concentra-
tion, hue, and colorfastness to light and laundering for three regional dyewoods (black
walnut, Osage orange, and eastern redcedar) on wool yarn. Dye concentrations were
pre-tested to find a standard depth of shade between mordanted and nonmordanted
yarns. Tests for colorfastness to light and laundering were performed according to
AATCC methods. Resulting colors for exposed and unexposed specimens were rated
using CIE L*a*b* values and descriptive statistics were used to examine directional
relationship within independent variables mordant and exposure (light and launder-
ing). Two-sample t test was performed to investigate the effect of a PAS mordant versus
no mordant on overall color difference between specimens exposed to light and
laundering. Findings indicated that dye absorption was improved with the use of a PAS
mordant. For yarns premordanted with PAS the dyewood colors became warmer. A PAS
mordant slightly improved colorfastness to light for black walnut and eastern redcedar,
but did not influence Osage orange which had a color change from bright yellow to
warm brown after exposure to light. Colorfastness to laundering improved only for
Osage orange with a PAS mordant.
Keywords: Natural dyes, Mordant, Biomordant, Tannin, Potassium aluminum sulfate,
Sustainability, Trees, Sawmill waste, Wool, Value-added
Open Access
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indicate if changes were made.
RESEARCH
Doty et al. Fash Text (2016) 3:22
DOI 10.1186/s40691-016-0074-9
*Correspondence:
knd36@cornell.edu
1 Cornell University, Ithaca,
NY, USA
Full list of author information
is available at the end of the
article
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Doty et al. Fash Text (2016) 3:22
that employ local and rural communities (Saxena and Raja 2014). When not sustain-
ably managed, communities can be economically exploited and natural environments
devastated. Socially responsible dyeing practices maintain local and indigenous dye tra-
ditions, support the local economy, and create educational opportunities (Bebali Foun-
dation 2013; Fletcher etal. 2012; Lopes Ferreira 2011). Beyond fiber dyeing, natural
dyestuffs have market potential in the food, beverage, and cosmetic industries (Saxena
and Raja 2014; Shahid and Mohammad 2013). Residual biomass on a small scale can be
composted but can be a challenge for larger scale production (Saxena and Raja 2014).
In addition, there is concern over the metallic mordant agent remaining in the effluent
water as well as amounts of water and energy needed for the mordant and dye processes
(Fletcher etal. 2012; Ismal etal. 2014).
A mordant is a substance that can form complexes between dye and fiber to increase
affinity, substantivity, and fastness properties (Dean 2014; Haar et al. 2013; Prabhu
and Bhute 2012). Potassium aluminum sulfate is the commonly used metallic mor-
dant for protein fibers with aluminum acetate seeing increased use for cellulose fibers
(Brown etal. 2010; Haar etal. 2013). e more toxic metallic mordants of copper, tin,
and chrome are not typically used by today’s craft and artisan dyer, yet these chemicals
are still being included in some natural dye research. Natural or biomordants from alu-
minum accumulating plants and high tannin content plants are being explored as substi-
tutes for the manufactured metallic mordants along with other alternative materials and
methods (Cunningham etal. 2011; Flint 2001; Ismal etal. 2014; Kadolph and Casselman
2004; Vankar etal. 2008). Trees with high tannin content are often classified as a sub-
stantive dye which do not require a metallic mordant, but may also be used as a mordant
depending on their tannin amount and chemical structure (Dean 2014; Ismal etal. 2014;
Prabhu and Bhute 2012). However, the addition of an aluminum metallic mordant when
dyeing with tree parts can improve colorfastness properties and shift color hue (Cardon
2007; Casselman 1993; Doty and Haar 2012).
e purpose of this research was to examine color properties of three regional dye-
woods in the form of sawmill waste with and without a mordant treatment of potas-
sium aluminum sulfate on wool yarn. e dyes were derived from Kansas black walnut
(Juglans Nigra), Osage orange (Maclura pomifera), and eastern redcedar (Juniperus vir-
giniana) and sourced from a sawmill in central Kansas, USA. Specifically, we analyzed
the impact of an aluminum mordant use on dye concentration, hue, and colorfastness
to light and laundering. Findings from the study will contribute to the understanding of
sawmill waste as a dyestuff and use of an aluminum mordant with select sawmill waste,
which may influence decision making for future research and dye practice by dye and
handcraft artisans. Sawmill and timber owners can benefit economically as sawmill
waste becomes a value-added product. Furthermore, this research contributes to the
dialogue of how plant dyes can impact aspects of the triple bottom line in niche markets.
Triple bottom line ofnatural dyeing
e following is organized by environmental, social, and economic sustainability of wool
fiber, mordant, and dyewood. While we recognize that the triple bottom line impacts are
often inter-related, we have presented each separately for ease of organization. Further,
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Doty et al. Fash Text (2016) 3:22
due to trees and wool being natural products and limited research on social and eco-
nomic values of natural dyeing, the environmental section is much longer.
Environmental sustainability ofnatural dyes
e environmental bottom line accounts for the sustainability of natural ecosystems
through maintenance, renewal, reparability, or replacement (Elkington 1998). Careful
consideration was taken when deciding upon the fiber, mordant, and dyes used in this
study and how they affect the overall natural cycle. Wool was selected for this research
due to its ability to absorb natural dyes and its renewable and biodegradable properties
(Burgess 2011). Wool is considered a sustainable fiber that is grown on sheep and can be
harvested without harm to the animal when ethical husbandry standards are met (Rus-
sell 2009). However, there is controversy over best practices to manage flystrike which
until recently was commonly managed by skin removal (Sneddon and Rollin 2010). Wool
fiber is used to make carpets, blankets, and garment textiles, it can be recycled into post-
consumer products such as insulation and geotextiles, and later be fully composted
back into the earth (Henry 2012; Russell 2009). Conversely, wool does have aspects that
negatively affect environmental sustainability. Sheep, like all livestock, produce methane
gas and require an extensive amount of land and water for nourishment (Henry 2012).
Predatory animals frequently target sheep, causing ranchers to use a combination of
lethal and nonlethal means to protect their investment (Sheep and Goats Death Loss
2010). is use of force by ranchers does correlate in many coyotes and wolves being
exterminated from their native hunting areas (Fletcher etal. 2012). During processing,
wool fiber requires water and energy to process the raw fiber into textiles and even more
water will be required during the consumer use phase for wool garments (Henry 2012).
Furthermore, wool textiles produce more methane during the disposal process when
decomposing in a landfill, although it should be noted that all natural and synthetic fib-
ers have this issue and that wool will decompose much faster than petroleum based fib-
ers (Russell 2009).
e metallic mordant used in the study was potassium aluminum sulfate (PAS) crystals
from Brenntag chemical distributor. According to the Safety Data Sheet provided by the
distributor, PAS is considered non-hazardous and non-toxic to the environment when
disposing by diluting with water and flushing in the sewer (Global Safety Management
2015). Even though PAS is used to purify water, there is environmental concern over
disposal of mordant bath effluent into the sewer or land and scholars are thus exploring
natural or biomordants as metallic mordant alternates with mixed results (Ismal etal.
2014; Vankar etal. 2008; Windholz 1983). Further, when mordanting is done separately
from dyeing it does increase water and thermal energy usage. Reuse and replenishing the
mordant bath can assist with this concern.
Sawmill waste from Kansas black walnut, Osage orange, and eastern redcedar timber
were the dyestuffs used in this study. Natural dyers have long used numerous parts of
trees (leaf, fruit, bark, root, and sawdust) for dye color due to their tannin content which
can act as a dye or mordant, particularly on cotton (Cardon 2007; Prabhu and Bhute
2012; Seth 2003). is use of varying parts of the tree as a dyestuff calls into question its
sustainability as an ongoing and viable product. e fruit of trees could be considered
the most sustainable, with new produce grown each year as well as being value-added,
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Doty et al. Fash Text (2016) 3:22
since the parts of the fruit that give the best color are usually inedible (e.g., black walnut
hulls and pomegranate rinds). Collecting fallen leaves and branches is another sustain-
able approach as long as there is enough windfall left behind for insect and wildlife bio-
diversity. Less sustainable would be the bark, roots, and heartwood of a tree. While it’s
possible to collect roots and bark from trees without harming the plant, it does take skill
and knowledge of a tree’s structural and nutritional needs and thus is not recommended.
A healthier practice would be to collect these items from trees already being harvested
for manufacturing or for timber control as was done in this study.
Natural dyes from trees pose interesting positive characteristics as a colorant, due to
their ability to produce a naturally occurring mordant called tannic acid which protects
the tree from various infectious microorganisms and prevents rotting (Hon and Shirai-
shi 2000). While many tannins give a brown cast to the dye color, some research sug-
gests that tannin mordants and dyes may darken dyed textiles as they age, instead of
the color fading due to exposure to washing and light (Cardon 2007; Richards and Tyrl
2005). Furthermore, previous research found that wool and cotton with a PAS mordant
and dyed with a tannin dye (i.e., black walnut bark and hulls) had improved colorfastness
to light and laundering (Doty and Haar 2012; Mirjalili and Karimi 2013; Sharma and
Grover 2011). Tannin amounts vary greatly between tree species and then amounts can
vary within a single tree depending on the time of year, age, moisture, temperature, and
soil condition (Flint 2001; Pizzi etal. 1986). As a general rule, hardwoods contain higher
tannin amounts than softwoods (Pizzi etal. 1986). Information regarding the amounts
of tannin in black walnut, Osage orange, and eastern redcedar was hard to obtain. How-
ever, recent research looking at the discoloration of hardwoods suggests that black wal-
nut heartwood contains 2 % tannin (Hon and Shiraishi 2000). While data from hide
tanning research performed in the 1910s suggests that Osage orange native to Texas had
upward of 10–11% tannin (Kressman 1916). Research performed in 1901 by the phar-
maceutical industry suggests tannin amounts in eastern redcedar at 2–8% depending
on the time of year when samples were collected (Peacock 1901). Naturally occurring
tannin in dyewood could possibly make for dyes that are durable without the aid of a
mordant which in turn could mean less effluents, even ones considered nontoxic, being
disposed into the environment following mordanting.
Two of the three dyewoods used in this study, eastern redcedar and Osage orange,
were selected due to their status as an invasive species. Eastern redcedar had an increase
in stock volume of 23,000% on surveyed Kansas lands from 1965 to 2005, effectively
decreasing the value of undermanaged pastureland (Moser etal. 2008). Once planted
for its excellent properties as a living fence line, the Osage orange can be a nuisance to
cattlemen as they tend to invade pastureland (Rutter 2013). Even though Osage orange
and eastern redcedar are currently invasive, this status would need to be monitored to
ensure environmentally balanced harvesting.
Social sustainability ofnatural dyes
e social bottom line encompasses social, ethical, and cultural issues of humans in
the form of public health, skills, and education, as well as a society’s health and wealth-
creation potential (Elkington 1998). Fletcher etal. (2012) state that from fiber through
dyeing, the worker’s health, safety, and exposure to toxins should be assessed, as well as
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Doty et al. Fash Text (2016) 3:22
fair labor practices. As with environmental sustainability, there is health concern over
chemical exposure and disposal of metallic mordant effluent (Ismal etal. 2014; Vankar
etal. 2008). e PAS crystals used in the study were rated as no significant risk to health,
while ScienceLab.com rated aluminum potassium sulfate as a moderate health risk in
case of ingestion, inhalation, and irritant to skin and eye (Aluminum potassium sulfate
2013; Global Safety Management 2015). As when working with any fine particle, proper
ventilation and protective glasses, gloves, and clothing are recommended. Naturally
dyed textiles are generally considered safe for the wearer, however they can also impart
positive finishing properties that are antimicrobial, insect repelling, deodorizing, and
UV-protective (Shahid and Mohammad 2013). Social responsibility was an overarching
theme of many of the presentations at the International Symposium and Exhibition of
Natural Dyes (2011), attended by one of the authors. e aims of Etno Botantica serve to
exemplify social, environmental, and economic efforts of natural dye groups represented
at the conference:
e program ETNO BOTANICA-natural dyes aims to contribute to the economic
sustainability of the native communities in the Amazonian rainforest and to fam-
ily organic farming, preserving the local culture, protecting their rights over their
knowledge, maintaining the existing biodiversity in their territories, as legitimate
cultural heritage for future generations. e entire line of products and services
ETNO BOTANICA is based on principles of social and environmental responsibil-
ity. e plant colorant extracts come from farming or extractive activities sustained
among local communities. e clean production process doesn’t generate toxic
waste, provides improved quality of life for producers and creates an alternative for
the conscious consumer (Lopes Ferreira 2011, p. 67).
Littrell and Dickson (1999) recognize the role of Alternative Trade Organizations
(ATO) in the social development and economic success of impoverished artisans in
developing countries, where natural dyeing may be included in the product development
process. Based on their extensive research, a fair trade model was developed encompass-
ing ATO core requirements, market objectives from artisan to consumer, primary activi-
ties, and skill requirements resulting in measureable direct outcomes. Such a framework
may be of benefit to future research measuring the social impact of natural dyes.
Economic sustainability ofnatural dyes
e economic bottom line is the value of financial, physical, and human capital, as well
as the economic benefit to the surrounding community and society (Elkington 1998).
e growth and maintenance of black walnut trees are encouraged in Kansas as a cash
crop, due to both a desirability as a hard wood and an edible fruit (Moser etal. 2008).
Whether dyewoods are harvested due to the maintenance of pastureland or because
of economic significance, sawmill waste from their timber could be a sustainable color
source for textiles while adding value to a local byproduct. Using byproducts and waste
from agriculture, forestry, and the food industry as natural dyes, may lower costs of nat-
ural dye production while consuming another industry’s waste (Shahid and Mohammad
2013). Dye waste pulp from the Indian Trapa fruit skin was effective in absorbing chro-
mium contaminated groundwater (Vankar etal. 2008). Mill waste from manufacturing
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Doty et al. Fash Text (2016) 3:22
have traditional uses such as paper products, particle board, and mulch but have been
further explored for less conventional projects such as bio-oil, making bricks, and as an
absorbent for water pollutants (Falk 1997; Crini 2006; Turgut and Algin 2007; Rout etal.
2009). Despite these varied uses wood products are often sent to the landfill or com-
busted for energy and fail to contribute any added value to their life cycle (Puettmann
and Wilson 2007). Other markets and applications for natural dyes include colorant for
cosmetics, food, beverage, hair, leather, paint, lacquers, and ink (International Sympo-
sium and Exhibition of Natural Dyes 2011; Shahid and Mohammad 2013).
Crop production of plant dyes for research, development, and large scale production
has potential to economically benefit communities if sustainably managed as with Cen-
tre of Research, Innovation and Technology Transfer in Horticulture (CRITT Horticole),
France. For 25years CRITT Horticole and offshoot company Couleurs de Plantes (since
2005), has conducted research and development of plant colorants, resulting in cultiva-
tion and production of extracts and pigments on an industrial scale (Brenac 2011). Some
other large scale production companies are Bleu de Pastel de Lectoure in France, Be Be
Cotton Knitting in Republic of China-Taiwan, Aura Herbal Textiles in India, Woad Cen-
tre in Britain, and PAI Natural Color in Italy. Research efforts to reduce overall process-
ing costs, energy consumption, and waste pollution through sonication methods in place
of traditional thermal methods are reported by Shahid and Mohammad (2013).
Methods
Black walnut, Osage orange, and eastern redcedar mill waste was sourced from a pri-
vately owned sawmill located near Galva, Kansas, USA. Millings from this location
contained all portions of the dye’s respective tree trunk (i.e., bark, phloem, cambium,
sapwood, heartwood, and pith). It cannot be determined as to the year or season when
the trees were felled or milled. e chemical compounds of trees that produce their
unique colors have not been identified. However, tannic acid present in those trees can
help dyeing the protein fibers. As the tannic acid is a weak acid, amino acids of the pro-
tein fibers would favor the protonated form in the acidic condition, and this might lead
to the facilitated chemical bonding with the color-producing chemical compounds.
e wool yarn was 30/2 worsted (style # SK 2/30 at owf of 5g) from Testfabrics, Inc.
All aqueous solutions were at a ratio of 80:1 (liquor to weight-of-goods) using reverse
osmosis water. Scouring soap was Orvus® paste (Dover Saddlery) at 2% owf and the PAS
crystal (Brenntag) mordant solution was 12% owf. Follows is an abbreviated presenta-
tion of the pre-test, scouring, mordanting, and dyeing procedures; detailed procedures
are presented by Doty (2015).
Tinctorial strengths differ between tree species and mordant treatment, resulting in
varied color depth and colorfastness properties when used at equal concentrations. Pre-
testing determined dyewood concentration required for PAS mordanted and nonmor-
danted fibers to produce visually comparable depth of shade according to the American
Association of Textile Colorist and Chemists (AATCC) standard depth scales (AATCC
2009). See Table1. All test samples were scoured, then half of the samples were ran-
domly assigned to one of three mordant bath treatments all with PAS at 12% owf. For
each dyewood, three mordanted and three nonmordanted samples were randomly
assigned to one of six dye baths and dyed using the predetermined concentrations
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Doty et al. Fash Text (2016) 3:22
(Table1). Scouring, mordanting, and dyeing was conducted using an Atlas Launder-
Ometer in order to maintain temperature and agitation.
Dyed specimens were subjected to tests for colorfastness to laundering and light
according to AATCC Test Method 61-2007 Colorfastness to Laundering: Acceler-
ated, Test No. 1A and AATCC Test Method 16-2004 Colorfastness to Light, Option 3
(AATCC 2009). Laundering was conducted using an Atlas Launder-Ometer which
simulated five hand launderings at low temperature (40±3°C) using individual stain-
less steel canisters. Light testing was conducted by Atlas Weathering Company using an
Atlas Xenon Weather-Ometer, which determined fading after exposure to 20 AATCC
fading units (AFU) or approximately 21.5h (AATCC 2009).
Prior to and following exposure to laundering and light, CIELab ratings were taken,
determining the specific color parameters lightness (L*), greenness-redness (a*),
and blueness-yellowness (b*) (Tables2, 3). A RM200QC Imagining Spectrocolorme-
ter (X-Rite, Michigan, USA) was used to obtain CIELab ratings. According to Marcus
(1998), ratings indicate for L* the higher the number the lighter the color, with black at 0
and white at 100. For coordinate a*, red is +a* and green is –a*; for coordinate b*, yellow
is indicated by +b* and blue is indicated by –b*.
Descriptive statistics (mean and standard deviation) for L*a*b* coordinates were used
to examine the directional relationship within the independent variables mordant and
exposure (light and laundering). Two-sample t test was performed to investigate the
effect of a PAS mordant versus no mordant on overall color difference between speci-
mens exposed to light and laundering, where the overall color difference Δ E was calcu-
lated by:
Δ E=
(L1−L2)2+(a1−a2)2+(b1−b2)2.
L1: L′ value of exposed specimen, L2: L′ value of unexposed specimen, a1: a′ value of
exposed specimen, a2: a′ value of unexposed specimen, b1: b′ value of exposed specimen,
b2: b′ value of unexposed specimen.
Table 1 Dyewood concentrations andstandard depth of shade to achieve comparable
color depth betweenpotassium aluminum sulfate (PAS) mordanted andnonmordanted
wool yarn
The depth of shade scale consists of six designations; there is “standard depth” at 1/1, “double depth” at 2/1 that is darker
than standard depth, and fractional depths with 1/3, 1/6, 1/12 and 1/25 that are lighter than standard depth, with 1/25
being the lightest
Dyewood andmordant type Concentration toowf(%) Standard depth
Black walnut
PAS mordant 100 1/12
Black Walnut
No mordant 200 1/12
Osage orange
PAS mordant 40 1/1
Osage orange
No mordant 50 1/1
Eastern redcedar
PAS mordant 100 1/25
Eastern redcedar
No mordant 150 1/25
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Doty et al. Fash Text (2016) 3:22
Table 2 Descriptive statistics forL*a*b* coordinates ofunexposed standards and speci-
mens exposed tocolorfastness tolight testing
Color swatches were generated with L* (lightness), a* (greenness-redness), b* (blueness-yellowness) rounded to the nearest
whole number using http://www.workwithcolor.com/color-converter-01.htm. The standard and specimens were 100%
wool yarn. Potassium aluminum sulfate (PAS) was the mordant
Dye/mordant Standard/exposed
tolight L a b Color swatch
Mean (SD) Mean (SD) Mean (SD)
Black walnut
PAS mordant Standard 61.32 (0.96) 11.59 (0.46) 24.70 (0.71)
Black walnut
PAS mordant Exposed to light 65.06 (1.17) 11.66 (0.56) 25.64 (0.88)
Black walnut
No mordant Standard 57.59 (1.43) 10.49 (0.50) 22.12 (1.25)
Black walnut
No mordant Exposed to light 62.54 (1.31) 10.59 (0.36) 23.43 (0.61)
Osage orange
PAS mordant Standard 69.49 (1.52) 8.37 (0.60) 56.03 (1.79)
Osage orange
PAS mordant Exposed to light 63.96 (1.11) 10.12 (0.26) 45.90 (1.06)
Osage orange
No mordant Standard 70.40 (1.67) 6.24 (0.39) 45.02 (1.76)
Osage orange
No mordant Exposed to light 63.66 (0.84) 10.24 (0.34) 35.29 (0.98)
Eastern redcedar
PAS mordant Standard 73.87 (1.39) 7.98 (0.19) 24.77 (0.74)
Eastern redcedar
PAS mordant Exposed to light 79.21 (0.95) 6.20 (0.49) 24.46 (0.87)
Eastern redcedar
No mordant Standard 71.06 (1.19) 9.08 (0.38) 14.93 (0.78)
Eastern redcedar
No mordant Exposed to light 75.93 (0.91) 6.37 (0.25) 18.22 (0.38)
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Doty et al. Fash Text (2016) 3:22
Table 3 Descriptive statistics forL* a* b* coordinates ofunexposed standards andspeci-
mens exposed tocolorfastness tolaundering testing
Color swatches were generated with L* (lightness), a* (greenness-redness), b* (blueness-yellowness) rounded to the nearest
whole number using http://www.workwithcolor.com/color-converter-01.htm. The standard and specimens were 100%
wool yarn. Potassium aluminum sulfate (PAS) was the mordant
Dye/mordant Standard/exposed to
laundering L a b Color swatch
Mean (SD) Mean (SD) Mean (SD)
Black walnut
PAS mordant Standard 61.32 (0.96) 11.59 (0.46) 24.70 (0.71)
Black walnut
PAS mordant Exposed to laundering 60.01 (0.69) 10.43 (0.36) 20.50 (0.47)
Black walnut
No Mordant Standard 57.59 (1.43) 10.49 (0.50) 22.12 (1.25)
Black Walnut
No mordant Exposed to laundering 58.30 (0.97) 9.20 (0.39) 20.20 (0.44)
Osage orange
PAS mordant Standard 69.49 (1.52) 8.37 (0.60) 56.03 (1.79)
Osage orange
PAS mordant Exposed to laundering 72.06 (1.04) 7.03 (0.82) 58.70 (1.54)
Osage orange
No mordant Standard 70.40 (1.67) 6.24 (0.39) 45.02 (1.76)
Osage orange
No mordant Exposed to laundering 68.88 (0.52) 7.26 (0.49) 39.81 (0.63)
Eastern redcedar
PAS mordant Standard 73.87 (1.39) 7.98 (0.19) 24.77 (0.74)
Eastern redcedar
PAS mordant Exposed to laundering 71.33 (0.88) 10.04 (0.39) 23.02 (0.66)
Eastern redcedar
No mordant Standard 71.06 (1.19) 9.08 (0.38) 14.93 (0.78)
Eastern redcedar
No mordant Exposed to laundering 70.82 (1.38) 9.29 (0.43) 12.99 (0.50)
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Doty et al. Fash Text (2016) 3:22
Results anddiscussion
Dye concentration
Black Walnut had a standard depth of 1/12 and required twice as much mill waste for
nonmordanted (200% owf) compared to PAS mordanted wool yarns (100% owf). See
Table1. Osage orange gave a standard depth at 1/1 using 50% owf for nonmordanted
and 40% owf for mordanted. Eastern redcedar had the lowest (i.e., lightest) depth shade
at 1/25 standard depth with 150% owf for nonmordanted and 100% owf for mordanted
yarn. In summary, yarns premordanted with 12 % PAS and dyed with black walnut,
Osage orange, and eastern redcedar required less dye than nonmordanted yarns to
achieve a comparable depth of shade. e effect was greater for black walnut and eastern
redcedar, requiring 100and 150% more dyestuff respectively for nonmordanted yarns to
obtain similar depth of shade compared with mordanted yarns.
Dye concentration andthe triple bottom line
e higher dyewood concentrations required of nonmordanted yarn to achieve compa-
rable depth of shade as the PAS mordanted yarn indicate that a PAS mordant treatment
enhanced dye adhesion thus requiring much less dyewood for black walnut and east-
ern redcedar. Even though Osage orange had comparatively less difference between PAS
mordant and no mordant, 10% is still considerable for natural dyes that will quantify
quickly when dyeing large amounts. is finding impacts the environmental bottom line
as trees are a natural resource that are slow to replenish. In addition, using less sawmill
waste means less biomass remaining after dye extraction that needs disposal or combus-
tion. While not as problematic to the craft dyer who can add it to the compost pile or
garden, it may impact large scale dyers. However, these larger scale dyers could yet again
find a use for the sawmill waste and have it made into paper products, particle board,
or mulch. Socially, there are concerns over the use of manufactured metallic mordants
which may impact health if proper ventilation, protection, and disposal is not practiced.
Conversely, the use of less dyestuff with aid of a metallic mordant would help maintain
local biodiversity and perhaps cultural heritage as there would be less need to cut down
vegetation for dyeing. e need for less dyewood with use of a PAS mordant increases
the already economic efficient use of sawmill waste and invasive tree species as dyestuffs.
e use of a mordant would add its cost along with the addition of the mordant treat-
ment step which uses water and thermal energy.
Color composition
Descriptive statistics (mean and standard deviation) for L*a*b* coordinates were used
to examine the directional relationship within the independent variables mordant and
exposure. Assessing this information allowed us to compare overall color change due
to the use of a PAS mordant. e PAS mordant influenced the color cast of wool yarns
dyed with black walnut, Osage orange, and eastern redcedar regardless of light exposure
or laundering (Tables2, 3). For black walnut, mordanted specimens were considerably
lighter, redder (a*) and yellower (b*) than nonmordanted. For Osage orange mordanted
specimens were yellower (b*) than nonmordanted. For eastern redcedar, mordanted
specimens were lighter, greener (a*) and yellower (b*) than nonmordanted.
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Doty et al. Fash Text (2016) 3:22
Exposure tolight
When looking at the independent variable exposure, all dyes had considerable effect for
L* (lightness) when exposed to 21.5h of light (Table2). For black walnut, both mor-
danted and nonmordanted specimens turned lighter and bluer (decrease in b*) after
exposure to light. For Osage orange dyed yarns, the color turned darker (lowered L*)
both for mordanted and nonmordanted specimens after being exposed to light. is
finding while unusual was not surprising as Osage orange is known to darken over time
(Cardon 2007; Richards and Tyrl 2005). Eastern redcedar dyed mordanted and non-
mordanted yarns turned lighter after exposure to light, and nonmordanted specimens
turned yellower while mordanted specimens showed little changes of b*. For eastern red-
cedar, mordanted yarns have a slight yellow cast (light tan color) and the nonmordanted
yarns a slight red cast (light pink mauve color). It is recommended for natural dyers to
use a PAS mordant if they want to shift the color of eastern redcedar from pink to tan.
However, the pink color of nonmordanted yarn may fade towards tan due to exposure to
light, so dyers should protect any project they want to remain pink from exposure.
For the independent variable Mordant, the PAS mordant influenced the color com-
positions of wool yarns dyed with black walnut, Osage orange, and eastern redcedar
prior to and following exposure to light. While all three mordanted dyewood yarns had
warmer (yellower and/or redder) tones prior to light exposure compared with nonmor-
danted yarns, eastern redcedar was both yellower and greener prior to exposure.
Exposure tolaundering
When examining the independent variable Exposure, laundering had a different influ-
ence than light exposure on color compositions of mordanted and nonmordanted dyed
specimens. For black walnut, mordanted and nonmordanted specimens were greener
(a*) and bluer (b*) when subjected to laundering (Table3). Mordanted specimens were
yellower (b*) than nonmordanted specimens but only before laundering. After launder-
ing, b* value became similar for both mordanted and nonmordanted. For Osage orange,
mordanted specimens were redder (a*) than nonmordanted before laundering, but a*
of both became similar after laundering. Mordanted Osage orange was also yellower
(b*) and nonmordanted Osage orange was bluer (b*) after laundering. For eastern red-
cedar, specimens turned lighter, redder, and bluer after laundering both for mordanted
and nonmordanted. When visually inspecting the specimens, mordanted and laundered
Osage orange was a brighter and clearer yellow when compared to nonmordanted. It is
recommended for natural dyers wanting to maintain a bright yellow to use a PAS mor-
dant on wool yarns dyed with Osage orange.
When examining the independent variable Mordant for PAS mordanted and laundered
yarns dyed with black walnut, Osage orange, and eastern redcedar they were warmer
(redder and/or yellower) than nonmordanted yarns, supporting previous research that
the use of a PAS mordant changes the color of natural dyes towards warmer (Doty and
Haar 2012; Haar etal. 2013).
In summary, the PAS mordant influenced the color cast subtly of the selected dye-
woods before and after exposure to light and laundering. For black walnut, the mordant
had a warming effect that remained after exposure to light, but not after laundering.
Osage orange was also warmer with the mordant, but the shift was not maintained after
Page 12 of 16
Doty et al. Fash Text (2016) 3:22
exposure to light and laundering. e mordant had a yellowing effect on eastern red-
cedar that became similar to nonmordanted with exposure to light but remained after
laundering.
Color composition andthe triple bottom line
e PAS mordant influenced color cast, however dependent upon the dye, the shift may
or not remain after exposure to light and laundering. In addition, when visually com-
paring resulting color, the difference may not be enough to warrant the use of a PAS
for color changing purposes. Elimination of the metallic mordant brings environmen-
tal value by reduction of water, thermal energy, and mordant disposal. As well as social
health value, by reducing potential exposure of fine particles. Alternatively, there is
social value in understanding the subtle influence of PAS on colorcast following dyeing
and exposure to light and laundry which contributes to the dyer’s overall knowledge and
color expectancy from natural dyes. Which in turn may influence economic value by
providing a product that addresses consumer expectations for color consistency.
Colorfastness properties
Overall color difference of PAS mordanted and nonmordanted specimens were assessed
using Δ E before and after (1) exposure to light, and (2) laundering (Table4). Smaller Δ
E means less color change after exposure to light and laundering, which could be inter-
preted as better colorfastness.
Exposure tolight
For yarns dyed with black walnut and exposed to light, two-sample t test showed that
there is a significant effect (t(16)=2.01, p=0.061) of mordant treatment on the color-
fastness to light (mordanted ΔE=3.95 and nonmordanted ΔE=5.17), suggesting that
PAS mordanted yarn showed less color change after exposure to light than nonmor-
danted yarns (Table4). For Osage orange yarns exposed to light, t test suggested no
significant effect (t(16)=1.38, p=0.187) of mordant treatment (mordanted ΔE=11.70
Table 4 Two-sample t test results ofmordant type forcolorfastness tolight andlaunder-
ing ondyed wool yarn: colorfastness is indicated interms ofcolor dierence ΔE ofsamples
beforeand afterlight or laundering exposure
*p<0.05
**p<0.01
***p<0.001
Nonmordanted Mordanted t value
M SD M SD
Exposure to light
Black walnut 5.17 1.31 3.95 1.25 2.01*
Osage orange 12.52 1.14 11.70 1.35 1.38
Eastern redcedar 6.51 0.72 5.72 0.95 1.99*
Exposure to laundering
Black walnut 2.56 0.71 4.61 0.50 −7.09***
Osage orange 5.57 0.57 4.26 1.07 3.25**
Eastern redcedar 2.35 0.70 3.83 0.60 −4.80***
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Doty et al. Fash Text (2016) 3:22
and nonmordanted ΔE=12.52) conditions. For yarns exposed to light and dyed with
eastern redcedar, there was significant effect of mordant treatment on colorfastness to
light such that mordanted (ΔE=5.72) yarns had less color change than nonmordanted
(ΔE=6.51) conditions; t(16)=1.99, p=0.064.
Exposure tolaundering
For yarns dyed with black walnut and laundered, t test showed a significant effect
(t(16)=−7.09, p=0.000) of mordant treatment on the colorfastness to laundering, sug-
gesting that nonmordanted (ΔE=2.56) yarns outperformed (i.e., had less color change)
mordanted (ΔE= 4.61) (Table4). For yarns dyed with Osage orange and exposed to
laundering, t tests indicated significant difference (t(16)= 3.25, p=0.005) that mor-
danted (ΔE = 4.26) yarns had less color change than nonmordanted (ΔE = 5.569)
conditions. For eastern redcedar yarns exposed to laundering, the difference between
mordanted and nonmordanted was significant such that nonmordanted (ΔE=2.35)
yarns had improved colorfastness to laundering over mordanted (ΔE=3.83) conditions;
t(16)=−4.80, p=0.000.
In summary, mordanted black walnut and eastern redcedar dyed wool yarn had less
color change compared to no mordant for colorfastness to light, while colorfastness
to laundering had less change for nonmordanted. ese findings are similar to prior
research with black walnut bark dyed on wool gabardine fabric where mordanted had
improved lightfastness with no difference between mordant treatment for exposure to
laundering (Doty and Haar 2012). Colorfastness to laundering results for Osage orange
indicated mordanted had less color change than nonmordanted, however exposed yarns
were significantly darker instead of the more typical lightening of hue. While colorfast-
ness to light for Osage orange was not significantly different, the overall color change
was also slightly darker. is finding while unusual was not surprising as Osage orange is
known to darken over time (Cardon 2007; Richards and Tyrl 2005).
Colorfastness andthe triple bottom line
Overall, colorfastness to light and laundering findings indicate mixed results for color
change when using a PAS mordant for the selected mill waste, however any improve-
ment to colorfastness is considered positive. us, using a PAS mordant may be prefer-
able as lightfastness improved for black walnut and eastern redcedar, while washfastness
improved for Osage orange. Improved colorfastness properties may enhance sell-ability
of dyed products as consumer concern for color longevity is addressed. Environmentally
and economically, the use of a premordant does increase cost and the amount of time,
water, and thermal energy required. Future studies could evaluate adding the mordant
to the dye bath, instead of as a pretreatment. As noted prior, there is growing concern
over disposal of any residual manufactured metallic mordant and its impact on the envi-
ronment and community health. As we did not measure the amount of remaining PAS
mordant from a 12% owf mordant bath, we cannot provide insight to this concern. A
possible social impact of introducing use of a PAS mordant is that such practice may
not be conducive to long standing natural dye traditions and if accepted could change a
cultural heritage.
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Doty et al. Fash Text (2016) 3:22
Conclusions
Findings from this study indicate that use of a PAS mordant does influence dye con-
centration, hue, and colorfastness to light and laundering of sawmill waste dyed wool
yarn with implications for the triple bottom line. Perhaps the most important finding
is that the PAS mordant decreased the amount of sawmill waste dyestuff by 10–150%
to achieve expected color depth. As trees are slow to replenish, using less and using an
existing timber byproduct as dyestuff has environmental and economic value. Using
invasive tree species also helps the environment by assisting to balance prairie and pas-
tureland ecosystems.
e influence of PAS on hue and colorfastness had mixed results. e PAS mordant
had a warming effect on all of the dyewoods that was minimized for black walnut after
laundering, while eastern redcedar’s cast was reduced after light exposure. Regardless
of mordant type, Osage orange darkened from a golden yellow to a tan/brown follow-
ing exposure to light. Colorfastness to light was enhanced with a PAS mordant for black
walnut and eastern redcedar, while Osage orange had a significant difference from laun-
dering but not for light. While any improvement to colorfastness is viewed as positive,
the mixed results and subtle overall visual color difference from mordant use may not be
enough to convince dyers to use a metallic mordant with tannin dyestuffs. e use of a
mordant does mean another step in the dyeing process that uses water, energy, and may
release unbound mordant chemicals into disposal systems, impacting both the environ-
ment and health of communities. Further, introduction of metallic mordant use may
impact the cultural heritage of traditional dye practices. Conversely, understanding and
utilizing a metallic mordant to shift color, improve lightfastness, and understand long
term color results may create social value through new knowledge, as well as economic
gain by addressing consumer concern over colorfastness of natural dyes.
is study did not measure tannin concentration of the sawmill waste nor amount of
PAS in the residual mordant solution. Measuring tannin amounts in future studies will
provide difficult to find tannin information on regional dyewoods and assist in under-
standing the role of tannin in interpreting colorfastness data. Future analysis of the
chemical composition of pre- and post-mordant solution will provide data on the actual
amount of PAS remaining in the waste water and thus assist in understanding of the
environmental impact of a manufactured metallic aluminum mordant. Finally, there is
a need to better understand social impacts of natural dyes upon the dynamics, health,
knowledge, and wealth creation for families, communities, and cultural traditions.
Authors’ contributions
KD designed the study, carried out the acquisition of data, and participated in the statistical analysis, and the construc-
tion and editing of the manuscript. SH participated in the design of the study, acquisition of data, and the construction
and editing of the manuscript. JK participated in the statistical analysis and editing of the manuscript. All authors have
read and approved the final manuscript.
Author details
1 Cornell University, Ithaca, NY, USA. 2 Kansas State University, Manhattan, KS 66506, USA.
Competing interests
The authors declare that they have no competing interests.
Received: 23 March 2016 Accepted: 25 August 2016
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Doty et al. Fash Text (2016) 3:22
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