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Distilling down the science of scents

Seven and eight-year-olds in Taranaki are investigating whether the aromatic plants they are distilling will give off-the-shelf cleaning products a run for their money.

Distilling group photo

Students at Toko School in eastern Taranaki have been exploring the science of extracting essential oils from plants like lemon, kawakawa, pine and mint, after setting up a distillery in their classroom.

Teacher Sue Fergus says this all started when she showed her students a scented candle that was given to her, which led to the kids wondering how the scent got put into the candle.

“I asked them, ‘how did people put the smell in it?’ and they said there were scented oils in it,” she says. “But then I asked, ‘but how do we get the oils?’ and one of my students, Isabella, said that her nana had a ‘perfume-making machine’.

“The rest of the kids didn't believe Isabella, but I told them that there is such a thing and that it’s called a distiller. And then I wondered if it might be possible for us to do that in class.”

Setting up the stillSue and her students enlisted help from scientist Jim Bennett of Still Valley and Liz Sinclair at Pihama farm, a local lavender farm, to find out how to extract their own plant oils.

“We went to a lavender farm visit after we had the idea to do the distilling. It was really fun because we got to pick the lavender,” says 8-year-old Luke.

They also decided to investigate whether any of the plant hydrosols (the liquid extracted by the still before the oil is separated out) would give cleaning products a run for their money and not be damaging to surfaces.

“The cleaner asked us if we could try and distil something that would help her clean the classrooms,” says Lucas, 8. “We're going to test all of the hydrosols to find out which of them work best and then give that one to the cleaner.”

Classmate Lockie adds, “Some of the paints, crayons and glue are really hard to get off and it takes ages to get the desks clean with normal cleaner.”

The process starts off with stripping the leaves off the twigs or stalks of the plants – in this case, rosemary from the school’s newly planted distillery garden and Japanese cedar.

Students stripping the leaves

Sue and the students then weighed each bowlful of rosemary before adding it to the distilling pot, and then added up the total weight – without calculators – once the pot was filled to the top. The Japanese cedar was added to a separate pot.

Next, the students put the lid on each pot, cranked up the heat on the hot-plate, and turned on the cold water hose. 

“My favourite part is when we put cold water into the condenser and it turns the steam into liquid” Maisie, 8, says.

The water cools the metal pipe at the top of each pot – the condenser – so that the temperature drop from boiling hot to cold creates the aromatic liquid hydrosol (also called 'distillate'), which then trickles down the pipe and into a glass measuring cylinder.

Collecting the distillate

The students then waited until the hydrosol reached the top of the cylinder and then poured it into a large conical flask. At set times, Sue and her students logged the pot temperatures and how many millilitres of hydrosol had been collected so far, through counting the number of times they poured the full (100ml) cylinder into the flask and working out the running total from that.

“Their maths has gone through the roof compared to before we started this project, and I think that’s because this is ‘real’ maths, rather than just being on paper,” Sue says.

“We’ve also learned heaps about solids, liquids and gases in relation to molecules as well as condensation. We put the hydrosol in the freezer to separate the oil from the water – because the water freezes but the oil stays at the top as a liquid that’s easy to just pour out.”

Distillate with oil on top

Once they had collected most of the oil from the plant via the hydrosol, the students took it in turns to smell the liquid.

The Japanese cedar smelt quite citrusy, while the rosemary smelt strangely unlike rosemary. Sue explains that fresh distillates can smell distinctly different at first and that lavender, for example, is usually aged for at least a year before it smells how we expect it to.

Arlo, 8, says, “I liked distilling the mint because it was really strong and you could smell it from the back of the classroom.”

“Some oils can go on your skin too. We did the kawakawa because it is good for eczema,” says Isabella, 7. The class 'guinea-pig', Lucas, has been spraying it on and believes that it has helped clear up his eczema.

Casey, 7, adds, “My brother has eczema so he has started trying kawakawa. He says it makes him feel better too. I really like how the kawakawa smells too.”

Smelling the hydrosol

Sue and the students are now testing the different oils to check which is the best cleaner. They have tested lemon, lavender, bay laurel, mint, pine, rosemary and hinoki cypress.

"Rosemary seems the most effective at cleaning and most of the rest are great as a disinfectant," Sue says.

The students are now hoping to sell the oils and cleaning products they make, to raise enough funds to do more investigative projects like this in the future. For the Christmas season, they are distilling pine to sell with the name ‘Forever Christmas’.

Distilling group pulling faces

About the project

Toko school logo
This project is run by Toko School, with support from the Taranaki Participatory Science Platform.



Participatory Science Platform

The Participatory Science Platform supports collaborative projects that bring together communities and scientists or technologists on research investigating a locally-important question or problem.

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