Eucalypts of Narrogin - Art, Science and Story
Tannins
Tannic acid is used as a pre-mordant on cellulose fibres and fabrics before the alum mordant. Alum does not combine as readily with cellulose fibres as it does with protein fibres. Tannin has a great affinity for cellulose. Once treated with tannin, alum will combine well with the tannin-fibre complex.
Tannins can be clear or they can add a colour to the fibre.
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Australia once supported a substantial tannin bark industry based on Wattles and a number of other species, all harvested from natural stands. Our Dryandra Woodland National Park, the first such park in the Wheatbelt region, was initially set aside in 1934 because of its value as an area for brown mallet, in demand at the time for tannin production. Brown mallet (E. astringens) plantations still cover ~30% of Dryandra.
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Oak galls were a traditional source of tannin for dyers in the northern hemisphere. Galls also occur on some acacias. We wanted to use local tannins where possible.
Acacias local to Narrogin include A. microbotrya, A. saligna, A. acuminata and A. lasiocalyx. This work explores tannins derived from Acacia acuminata and Acacia microbotrya – leaf, bark and galls.
To Test Local Tannins from A. acuminata and A. microbotyra
1. The relative dyeing capabilities of three different cottons - homespun, un-bleached calico and bleached calico.
2. The merits of different Jam (Acacia acuminata) and Manna (Acacia microbotrya) wattle tannins – leaf, bark and galls.
3. The difference when using Aluminium sulphate/soda ash mordant vs Aluminium sulphate alone vs no mordant.
4. The colours obtained when modified with alum, soda, iron, copper, tannin or left unmodified.
The dye used was Eucalyptus cladocalyx leaf dye.
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A. microbotrya galls. These are collected green, fermented and used at a strength of 10%.
What did we find?
1. We chose homespun cotton as it gave a whiter backgound.
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3. We chose to use alum sulphate.
4. We decided to use tannin and metallic mordants for our future tests.
We decided to use A. microbotrya galls which are readily available and do not damage trees.
