Botanical Printing, Eco Printing, Botanical Dyeing, Eco Dyeing, Botanical Inks – just some of the terms being used to describe this increasingly popular and exciting approach to transferring plant colours and patterns onto fabric and paper. The varying methods use leaf and flower cuttings to extract colour and ghost-like images of the foliage.
The potential of Botanical Eco printing on fabrics and paper are endless. The infinite choice of flora will provide innumerable variations depending on the mordants and methods used to extract the colour. Using the simplest recipes to begin with and careful record keeping will help to develop knowledge and progress to greater experimentation.
Using Mordants for Botanical Eco Prints
Botanical printing uses different mordants to help form chemical links between the fibre and the colourant to create light and wash fast colours.
Alum (Aluminium Potassium Sulphate) is often referred to as a mordant in Botanical printing, it is used as an ‘assistant’ in altering the chemistry of cellulose to allow dye colours to bond to the fibre (mordants chemically attach to the fibre and then attach to the colour as a ‘bridge’). It is widely used in natural dyeing and tanning, and is present in many products including cosmetics and food preparation. It is commonly used for preparing fabrics and paper for Marbling and Printing, and improves colour absorption for these materials.
Tannins are found in leaves, wood, bark, tea and fruit. One specific tannin, Tannic acid is used to mordant cellulose (cotton & linen) fibres and fabrics before using Alum to prepare the cellulose to bind chemically with the naturally occurring dyes in plant materials. This is because Alum does not react with cellulose fibres in the same way as it does with protein fibres. In Botanical Printing, the source of Tannins is from the leaves and some flowers with the Alum used in the substrate or blanket to complete the reactions.
Likewise, colours become better fixed when Iron, Copper, Tin and Titanium Oxalate are used as a mordant. Iron will darken the colour, known as ‘saddening’, and shift yellows towards orange, reds to brown and purples to black. It works particularly well with tannins, such as Oak Gall, taking the pale brown from purples on cotton and linen through to near black on silk and wool.
Copper alters the colour to add shades of light green through to khaki, olive and bronze. Tin used in very small quantities will encourage reds but can make materials brittle, and Titanium Potassium Oxalate will bring out oranges from tannin in leaves.
Auxiliaries to consider include Soda Ash, an alkali for forming alkaline solutions etc, can improve the effectiveness of mordants on cellulose fibre (cotton and linen) and act as a colour modifier, Citric Acid or White Vinegar to alter the pH in water and potentially colour results, and Cream of Tartar, which when used with Alum, can increase the potency of mordants and colour absorption on protein fibre such as wool and silk.
These auxiliaries can be used during the pre-wash, dissolved in the mordant solution, or as a rinse solution after steaming/cooking.
It is very important that fabrics are dirt and grease free as this will hinder the absorption of the colour. Synthrapol can be used to clean the materials and work as a wetting agent (a surfactant). It removes oils effortlessly and can lower the surface tension between the fibres and the leaf colourant. Add half a teaspoon of Synthrapol per 5 litres to the mordant solution.
Materials for Botanical Eco Printing
It is best to use materials with natural fibre content as the substrate for producing prints. Natural fibres absorb moisture more efficiently which ensures that the mordant is effective in helping to transfer the colour. There are two natural fibre types; protein and cellulose.
Protein fibres come from animals and include wool from sheep, white silk from the Bombyx Mori moth (other Bombyx moths produce a wide range of fibres for spinning and weaving into silk fabrics, each has different attractive attributes), and hair from goats, alpaca and camel. Cellulose fibres are prepared from plants such as cotton and flax (linen).
The materials most often used for Botanical printing are silk and cotton or linen fabrics. Watercolour paper with a high cellulose content is also used to good effect; the paper is strong and does not fall apart when wet. Finely woven fabric with a high thread count will improve the clarity of the print, while more open fabrics will result in less detailed images. Printing onto woollen fabrics (such as felt) is also possible; the transfer from the foliage is improved by ensuring it laid as flat as possible against the surface of the fabric.
Fabrics can be dyed prior to printing with natural dyes or synthetic dyes or they can be left undyed to show off the clean bright colours that are achieved from petals and some leaves.
Choosing your Leaves or Flowers for Print
Pick a selection of leaves from the plants and trees in your garden or venture out to parks, along canals, or into woodland. Be aware that some fruits such as the Foxglove and Deadly Nightshade are poisonous and some leaves are irritants such as nettles and rue.
Do a little research and find out which leaves, such as Oak and Grape, are rich in tannins. The colours can range from pale yellow through to brown. Others leaves, such as Goldenrod and Woad will provide you with greens, while Lilac can produce a citrus yellow.
The final results are determined by which part of the plant is used (the stem, leaves and petals will often give different colours); by which mordant is used and on which substrate (cellulose and protein colours will colour differently); and the final method of how the colour is extracted.
Extracting the Colour from the Foliage – Curing
The success of an Botanical Eco print can be dictated by the method used to extract the colour. The object is to ensure that the leaf or petal is pressed close to the damp mordanted fabric or paper. A popular technique is to arrange the foliage on half of the material before folding it over into a sandwich (alternatively a barrier sheet of plastic, paper or fabric is placed over the leaves). It is then rolled tightly around a pipe or stick and bound with string. The parcel is then placed above boiling water in a steamer for 1-2 hours and allowed to completely cool before opening.
The key to a successful print is ensuring that the fabrics or paper remain damp. Spraying your materials with mordant water will help to keep them damp while you work.
Other techniques for extracting the colour include:
- Sandwiching the leaves between two layers of fabric and pounding them with a hammer.
- Placing a differently mordanted sheet of fabric (a carrier blanket) over the leaves before rolling. The “iron blanket” will draw the colour from the leaves to the edges to create an outline shape of the leaf. Soaking your fabric in tannin before placing the leaves and layering with the iron blanket will give a dark background where the fabric was not covered with leaves. “Made by Barb” demonstrates this method in her Blog post The Mysterious Iron Blanket.
- Making stacks of mordanted watercolour paper with foliage between the sheets, placing them on a cooling rack and weighing them down with bricks. The cooling tray is then placed in a baking tray with water beneath the rack and covered with foil before “cooking” in the oven. Variations include placing the stack in an airtight bag and microwaving (see below for instructions) or submerging the stack in Alum solution and boiling it.
- Microwaving provides intense heat very quickly. If you choose this method it is essential to prevent moisture escaping from your parcel. Wrapping it in cooking cling film or using an airtight bag will ensure the moisture turns into steam. It is the heat from the steam that creates the chemical reaction of extracting the colour. Heat on high until the bag or cling film inflates with steam, turn the setting to “Defrost” and continue to cook until the parcel begins billow up again. Remove from the microwave and leave to cool (overnight if you like!) while the colours continue to absorb into the material.
- Using different items to wrap your work around can alter the outcome of the Botanical Eco print. Copper from Copper piping can alter the colours, while wrapping around a piece of hose pipe will give the parcel flexibility and allow you to bind it very tightly. Wooden dowels can be made from old curtain poles or dropped tree branches and binding materials can vary from cotton butchers string, copper wire, bandages, shoe laces and cling film.
- Experimenting with the method of curing the parcel can include burying it for a number of weeks, allowing it to bake in the sunshine or ironing between two sheets of paper.
Botanical Eco Printing in Summary
There are no hard and fast rules for this technique, you can use the internet to find a vast array of recipes from all over the world! It has evolved with much experimentation, repetition and note taking. All results will be determined by a number of factors – what type of material was used, how it was mordanted, which foliage was included, and how it was cured.
We recommend that you use the most simple of the processes for your first print and build your knowledge from there.