Teacher background information

This elaboration allows students the opportunity to explore a range of separation techniques developed and utilised by Aboriginal and Torres Strait Islander peoples across Australia for a variety of purposes. Students have opportunities to investigate the scientific principles underlying these techniques, and explore examples of specific separation methods developed by First Nations’ Australians that enable the procurement and processing of resources necessary for everyday life and for survival in times of food and water shortages.

Aboriginal and Torres Strait Islander societies have long been adept at using numerous separation techniques, both wet and dry, to isolate and extract components of mixtures, including hand-picking, winnowing, yandying, sieving, filtering, straining, cold-pressing and steam distillation. 

These techniques are essential for processes such as preparing foods, purifying water for drinking and creating medicines. These practices and technologies utilise readily available local resources and require a complex understanding of the components making up particular mixtures and the most effective techniques for their separation.  

Hand-picking is the separation by hand of desired particles from a mixture containing undesired particles. It is based on the principle that particles can be easily distinguished by visual characteristics, such as size, shape or colour. The desired particles may be a food source, medicine, mineral or other valued resource or commodity. Alyawarre, Anmatyerre, Warlpiri and Pitjantjatjara Aboriginal peoples in the central desert regions of Australia frequently use this technique, for example, in the collection of desert raisins (Solanum centrale). The stalks and bad fruit are separated and discarded and the ripe fruits are separated from unripe ones.  

Winnowing is a separation method that is designed to remove lighter particles while maintaining heavier ones. It is commonly used in separating seeds from their outer shells or coatings (husks). The mixture of seeds and husks is placed in a specifically designed container, such as a koolamon. The word koolamon (or coolamon) is derived from the language of the Kamilaroi people of northern New South Wales and southern Queensland and is now in the Australian vernacular. The mixture is then thrown lightly into the air allowing the wind to remove the lighter husk particles while the heavier seeds fall safely back into the container.  

Aboriginal peoples, including the Alyawarre Aboriginal peoples of the Sandover River region in the Northern Territory harvest at least 36 different seed types as resources for food. Seed pods are collected and beaten with sticks to release the seeds within. The resultant mixture composed of seeds, pod fragments and debris from the ground (sticks, dirt, stones etc) is then winnowed to leave just the seeds behind.  

Yandying is akin to the process of gold panning, and like winnowing is used to separate less dense particles from denser, desirable ones. A common purpose for yandying would be to separate sand, dirt or ash from seeds. In this technique, a mixture is placed in a wooden container called a yandy, a word used by the Yindjibarni people of the Pilbara region in Western Australia to describe a shallow dish similar to a koolamon, as well as the process of separation for which it is primarily used. The yandy is held in the hand, raised in one corner, and then gently shaken back and forth forcing the smaller and denser particles to collect at the bottom while the larger and less dense particles remain higher up.  

Traditionally, Yankunytjatjara Aboriginal peoples in north-western South Australia relied heavily on mulga seeds as a food source. To prepare seeds for consumption they would undergo a double yandying process. The seeds would initially be separated from their pods through threshing and rubbing and then yandied to separate them from the pod fragments. The seeds would then be baked in hot sand and ashes, requiring an additional yandying process to remove sand and ashes. Finally, the seeds would be ground and moistened into a paste for consumption.  

Sieving, filtering and straining are methods that allow for the separation of solid particles of different sizes or for the separation of liquid from solid matter using a porous device, mesh or a perforated container. A mixture is sieved, filtered or strained to allow the smaller particles, or liquids, to pass through while keeping the larger particles or solids in place. If the purpose is to separate the liquid for further use it can be collected in a container placed underneath the separation device. The effectiveness of these techniques depends on the size of the holes in relation to the size of the particles to be separated. 

A practical example of filtering can be found in southwest Victoria, where in traditional times, Gunditjmara Aboriginal peoples used flowering honeysuckle cones (banksias) to filter water from muddy pools when clean drinking water was unavailable. The cone would be placed in the mouth and used like a filtration straw, separating impurities to provide clean drinking water.   

Cold-pressing is a technique that uses pressure to extract the most medicinally rich oils from plant matter without heating the organic matter. The plant matter is ground to a pulp prior to pressing; the pressing process then extracts the water content producing a juice. Macadamias and coconuts are two examples of plants that were traditionally processed widely for their oil using the cold-pressing separation technique.  

An example of cold-pressing used by Aboriginal peoples is in the medicinal use of Eremophila alternifolia, a shrub that is endemic in areas between the far west of New South Wales, the far south of the Northern Territory and the southern half of Western Australia. Its leaves are finely chopped and then mashed into an oily paste which is then used as a rubbing medicine or tied around the head with grasses as a poultice.  

Distillation is a process that separates a mixture of liquids based on their differences in boiling points. A related technique, steam distillation, is often used to extract aromatic oils and other substances from plant matter. In contemporary practice, the plant material containing the often medically-active substance is immersed in water and boiled. The increased temperatures achieved by boiling rupture the plant cells, releasing the oils within. The water vapour carries small amounts of the vaporised aromatic compounds into the gas phase, where they may be used directly by inhaling or wafting over afflicted body parts. Depending on the type and quantity of oil present in the plant material, the oil may accumulate in liquid form at the water surface and can be collected by decanting. Traditionally, the extraction process was achieved by placing large amounts of fresh wet plant matter over cool fires to steam the leaves, releasing the medicinal vapours. Treated individuals were placed over the fire exposing them directly to the medically active components in a kind of ‘steam bath’. Eucalyptus and tea tree leaves are now used by people around the world and inhaled as treatments for coughs using the same vapour delivery method.  

The main purposes of the above separation methods were for purifying water, processing foods and extracting medicinal components. At the time of colonisation, Aboriginal and Torres Strait Islander peoples’ separation methods were keenly noted by Europeans. The skills of Aboriginal and Torres Strait Islander peoples such as in yandying, were quickly recognised and adapted for mining, and often allowed First Nations’ Australians to generate an income in times where no or limited employment opportunities existed. An example of this is in North Queensland where Aboriginal peoples owned and operated tin mines utilising traditional and modern methods to extract and separate minerals.  

By exploring the range of separation techniques employed by Aboriginal and Torres Strait Islander peoples in different environments for different purposes, students deepen their understanding of the scientific principles underlying these techniques. Students also gain an appreciation of the importance of separation techniques in traditional and modern societies.