By: Anne Vuorema
Research Scientist Anne Vuorema of MTT Agrifood
Research Finland proves in her doctoral dissertation that glucose can serve as
a reducing agent of indigo. This finding is significant for devising more
ecological dyeing practices for the textile industry.
Indigo is a vat dye and it needs to be reduced
to its water-soluble leuco-form before dyeing. This allows the actual dye to
pass on to textile fibres. Glucose is known to be a good reducing agent, and
Vuorema's work demonstrates that it also works with indigo.
Glucose dyeing seems to suit plant-derived
fibres, such as cotton and flax, which withstand a high pH (11-12). However, at
this stage it cannot be recommended for animal fibres, such as wool and silk
(which can only withstand a pH of up to 9).
A specialized field with few experts
Anne Vuorema's field of study is not widely
known, and there are perhaps only 20 researchers worldwide whose work focuses
on plant-derived indigo. Vuorema and MTT launched the indigo research as part
of the EU Spindigo project in 2001-2004. The project prompted questions which
Vuorema attempted to answer in her dissertation.
Vuorema works as an external researcher for MTT
Plant Production Research. The Finnish Cultural Foundation granted a
scholarship for her doctoral dissertation in three years. In 2007, the Academy of Finland funded her research at the University of Bath in England. This is where she
has conducted most of her electrochemical research. Vuorema conducted her
research at the University of Bath and the University of Reading in 2004-2006.
Professor Philip John at the University of Reading was the leader of the
Spindigo project and he also supervised Vuorema's research in Reading.
Anne Vuorema's research provides answers that
enable researchers to improve the extraction of indigo from the leaves of dyer's
woad (Isatis tinctoria L.). Her work enhances the energy efficiency of dyeing
and can potentially promote the profitable use of plant-derived indigo.
Dyer's woad is the best known of all indigo-producing
plants in Europe. Plant-derived indigo was commonly produced until the early 20th
century when synthetic indigo replaced it. The blue dye used in jeans, for
instance, is nowadays synthetically produced from oil, in a process which
wastes non-renewable natural resources and burdens the environment with
synthetic chemicals.
Electrochemical reduction enables a clean
process
In her dissertation research, Anne Vuorema
developed a new electrochemical method for determining the purity of indigo.
She reduced plant-derived indigo using glucose and measured the indigo
concentration in the mixture using a new method. This is a great improvement in
determining the purity of plant-derived indigo.
The method can also be applied to assess the
purity of other similar chemicals.
"The degree of purity of plant-derived
indigo is fairly low. Crude indigo has a dye content of less than 50%, while
synthetic indigo has a dye content of over 95%. The impurities and means to
reduce them are not yet well known," Vuorema explains.
Businesses look for guaranteed standard quality
of dye. At the same time, ecologically geared companies are looking for
increasingly natural methods for dyeing fabrics, among other things.
