Dr. Rangi Te Kanawa: Conservation in Action

Combining cultural and chemical knowledge to preserve textiles and traditions.


This is Dr. Rangi(tuatahi)

Te Kanawa’s pepeha – a traditional introduction for Māori (the indigenous people of New Zealand).

The pepeha highlights one’s connections to people, place, and the environment.

*Note that in Māori, the bar over a vowel (ā) means to draw it out (ā=aa).

Table of Contents:

The Piupiu

Starting with the Basics... and Acids

Tied to the Earth

Tānekaha Dye

Preserved for the Future


The Piupiu

As she carefully examines the frayed edge of a traditional Māori skirt (called a piupiu), Dr. Rangi Te Kanawa is transported back to her childhood. She remembers watching a fantail bird from the window, listening to its energetic twittering and the gentle conversation of her mother and grandmother (Nana) as they worked in her living room. The two women were weaving, their hands skillfully twisting harakeke (New Zealand flax) fibers into threads and the threads into intricately patterned cloaks.

A black and brown skirt has a woven waistband with long ties on each end. The skirt is made of dyed woven fibers and strings of decorations that are like long, cylindrical beads.
Piupiu is a short kilt usually made of strips of flax and worn by Māori for native dances and on ceremonial occasions (Wikimedia)

Rangi’s mother (Diggeress Te Kanawa) and her Nana (Rangimārie Hetet) were experts in dyeing and weaving. Through their teaching and leadership, they helped preserve the mātauranga Māori– the traditional ways of knowing and learning. Mātauranga Māori is often interdisciplinary, combining language, medicine, art, and education. It revolves around the Māori community’s relationship with their land and environment. Rangi’s background in these traditional practices provides her with valuable context as a scientist who studies Māori textiles.

Peering closely at the fraying skirt, Rangi notices that the dyed-black fibers are the ones that seem to be breaking apart, while the red and yellow fibers are still intact. Rangi is a conservator—someone responsible for the repair and preservation of cultural arts and artifacts. She earned her PhD investigating how black dyes made from iron-rich mud (paru) often contain acids that degrade textiles. She and her colleagues have developed methods to preserve and restore these works by neutralizing the acidity of the original dyes.


Starting with the Basics... and Acids

If a substance is referred to as acidic or basic, what does that mean? These words describe where something falls on the pH scale, which ranges from 1 to 14. Scores less than 7 are categorized as acids and scores more than 7 are categorized as bases. Vinegar (and anything with a sour taste*) is acidic, whereas most cleaning products like soap are basic. A score of exactly 7 is considered neutral, and drinking water is usually pretty close to neutral.

The reason that acids and bases are different is because they have a different number of hydrogen ions. A hydrogen atom is made of one proton and one electron, so a hydrogen ion is a proton without an electron attached. Different concentrations and availabilities of hydrogen ions cause substances to react to each other in various ways– acids have a lot of hydrogen ions (and therefore a net positive charge) to donate to other molecules. Bases, on the other hand will readily accept spare hydrogen ions from their environment (and generally have a net negative charge).

All these extra hydrogen ions in acids will corrode other substances by stealing electrons and weakening the chemical bonds and overall structure. Bases (e.g. bleach and ammonia) are useful for cleaning because their deficit of hydrogen ions makes them bond well to oils and fats.This also makes bases feel slippery to the touch because they bond to oils that form layers which slide across each other. Combining an acid and a base in the correct amounts can neutralize the solution. The acid donates all of its spare hydrogen ions to the basic molecules, so if the hydrogen ions are exactly balanced, the resulting mixture has a net neutral charge.

*Humans are very good at tasting the pH of mild acids (like lemon juice or vinegar) but please don’t use taste as a general pH indicator! All acids are sour, but some of them you’d only be able to taste once in your life (like the incredibly deadly sulfuric acid). And while most of our foods aren’t on the basic side of the pH scale, humans can still taste bases as bitter. But the same warning is true for them- just cause our tongues can taste the bitterness of drain cleaner (a powerful base) doesn’t mean that our stomachs would be very happy if we did.


Tied to the Earth

Around the waistband of the piupiu, thin black fibers interweave with striking reddish-brown ones in a geometric pattern. The red color of these fibers comes from the bark of the tānekaha tree, also called the celery pine. Despite the name, this New Zealand “pine” is a unique species, not closely related to other plants with these names elsewhere in the world. This tānekaha red dye is culturally significant in Māori tradition and represents Papatuanuku, the Earth Mother.

Natural dyes are fascinating and deeply personal to Rangi. The mud and plants used for dyeing connect a garment and its wearer to the place where the materials were harvested. Dyeing with natural materials reinforces the cultural and spiritual connection to the land. But these dyes also can act like a fingerprint, with unique mineral and chemical traces that tie them to a specific location. Rangi hopes to develop chemical analyses to figure out where textiles came from by detecting these subtle traces. This could help determine the origin of many priceless garments (taonga) that have been handed down over generations or which have ended up in museums.


Tānekaha Dye

The process to make these beautiful red dyes has been perfected by generations of Māori weavers. First, they find a mature tānekaha tree and they cut a rectangular section of bark from it using a special hatchet. Traditionally, this wound is then patched with mud, to help the tree recover. In the coming weeks and months the harvesters will check on the tree to make sure it is healing and its bark is growing back.

Rangi adds, “And I’m pleased to say that when I’ve gone back to the tree, it appeared to have recovered.”

A piece of wood has been shaped and hollowed out. There is liquid in side, with brown foam on top. There is steam surrounding the vessel.
Dye extracted from tānekaha bark in an oko (the wooden vessel), brought to a boil by hot stones.

In the next step, they add water to an oko (a wooden vessel) and submerge the bark. Volcanic stones are heated in a woodfire and carefully placed into the oko, bringing the water to a boil. The hot water helps release the colorful chemicals (called tannins) from the bark, turning the water into a dye solution. The bark is left in the water overnight.

A hand is holding a plastic clip with several strands of twisted fibers attached. The fibers have taken on a reddish-brown color from the dye.
Twisted fibers dyed a reddish-brown from tānekaha bark.

The next day, the weavers transfer the dye solution to a new container. The braided fibers are then soaked in the solution overnight, changing the naturally pale fibers to an orange-brown.

The last step is a chemical reaction! By rubbing wood ash into the fibers, the weavers permanently bind the dye to the fibers. This changes the color from an orange-brown to a final reddish-brown. The ash-covered fibers are then rinsed with water and ready to be woven into a cloak.


Preserved for the Future

The Māori weaving practices are not only a beautiful form of art, but also showcase the rich scientific understanding of traditional knowledge. Māori weavers use their understanding of both biology and chemistry to pull these colors out of the natural world and into a beautiful piupiu. Dr. Rangi Te Kanawa continues to combine her chemistry research with the knowledge passed down to her from her mother and grandmother. Through her work, we've gained a deeper understanding and appreciation of traditional technologies, and the Māori community can continue to preserve precious textiles and connect with their history.

Adapted with permission from Galactic Polymath’s lesson: Colourful Solutions


Written by Matt Wilkins and Stephanie Castillo

Adapted by Madelyn Leembruggen

Edited by Taylor Contreras and Caroline Martin

Photos courtesy of Rangi Te Kanawa

Primary sources and additional readings:

Colourful Solutions by Galactic Polymath

Mātauranga Māori and science from the Science Learning Hub

Black is Back from the New Zealand Ministry of Education

Acids and bases - introduction from the Science Learning Hub

Harakeke under the microscope from the Science Learning Hub


Acids, bases, and dyes, all in your own kitchen!

Taste (15-30 minutes): Your mouth is an amazing, delicate chemical detector, and it can also be part of your home laboratory! Experiment with different combinations of acids and bases (all with edible chemicals) and how those chemicals affect your sense of taste.

Experiment (90-120 minutes): Make your own red cabbage litmus paper and then test ingredients in your kitchen to see if they are acids or bases.

Create (60-90 minutes): Use plant dyes and other natural materials to create colorful clothes that help you express yourself.