1. Fabric selection
Selecting the right fabric for the dye job is a crucial step as different fabrics can produce striking variations in the resulting pattern. Both protein based fibres (silk, wool) and cellulose based fibres (cotton, linen, hemp, etc) can be dyed in indigo and other natural dyes. We choose to use mainly cotton, linen or hemp for our projects with a preference for domestically produced handwoven and hand-spun fabrics. Fibre that has been spun and woven by hand tends to have fewer twists in the yarn which results in a heavier, fluffier and more open fabric profile that allows for a very attractive and dynamic absorption of dye.
Yarns that are woven into fabric on industrial looms are often coated with starch to make the weaving process run smoothly. This starch prevents the dye from properly adhering to the fibre. Fabric that has been woven by hand will also contain oils and contaminants that will adversely affect dye absorption. Before work can begin all of these contaminants have to be removed from the fabric by simmering it for an hour in a slightly alkaline soapy solution of water, soda ash and washing detergent. The fabric is then washed, dried and made ready for the next step in the process.
3. Pattern plotting
To create our patterns on cloth we utilize various techniques which all work by the same principle of allowing the dye to attach to some areas of the cloth while leaving other areas undyed. In order to expose some areas while resisting others the cloth is compressed in a way that is specific to each pattern and that process begins by plotting out a stitching template using a temporary fabric marker. Each pattern has a unique template with some patterns requiring a simple grid and others requiring more complex measurements. Depending on the size and complexity of the pattern this step can take anywhere from half an hour to half a day to complete.
Once the fabric is marked the stitching process begins. The fabric is stitched according to the template using thread and needle. Some patterns require stitching done in straight lines at specific intervals while others require the threads to deviate from a straight path for more intricate designs. This step is usually the most time-consuming in the entire process. A single yard of stitch-resisted fabric can take anywhere from one day to one week to stitch. Care must be taken to avoid threads interfering or catching on one another as this will cause the fabric to compress incorrectly.
5. Thread pulling
After the stitching is completed each of the threads must be pulled. This action causes the fabric to fold in on itself in various ways depending on how it was stitched. Only the sections of fabric that are left exposed will receive the dye. Variations can be achieved here by playing with the thread tension as this can affect how far the dye can penetrate into the folds. Each of the threads is knotted to keep the fabric compressed.
An alternate way of compressing fabric involves pleating and folding it in various ways. This collection of techniques is called “Itajime” as opposed to the previously described “Nui-Shibori” or stitch-resist techniques. As Itajime forgoes the plotting and stitching process of Nui-Shibori altogether it typically requires significantly less time while still delivering visually pleasing results.
Books have been written on the intricacies of indigo dyeing alone and in the 21st century the process still remains somewhat of a mystery. For our purposes here we will just say that the indigo must be kept in a good condition because a bad dye job at this stage can irreversibly ruin days/week’s worth of work. It is kept in a good condition by judging the alkalinity, oxygen levels and amount of pigment remaining in the vat and playing with all the possible variables to achieve a good balance. Indigo vats are traditionally kept in a fermentation stage but modern advances in chemistry have made the process easier by allowing the variables to be better controlled through the use of chemicals like sodium hydrosulfite. Our current method of maintaining our indigo vats involves the use of sodium hydrosulfite, soda ash and natural indigo pigment while we learn more about traditional techniques in order to transition to a full fermentation-style system in the future.
Like the steps leading up to it indigo dyeing takes time. The compressed cloth bundle must first be soaked overnight in water to help it take up the dye better. It is then carefully lowered into the indigo where it is gently massaged to help the dye penetrate into the folds. When the fabric is taken back out of the vat it will first appear to have a muted green colour, but as the indigo slowly oxidises in the air the shade will begin to shift towards a vibrant blue. To gain even distribution of colour and a rich deep shade this immersion-oxidation process must be repeated to build up layers of pigment on the fibre. This cannot be rushed. If one layer is not properly oxidised onto the fibre it will end up washing off along with any subsequent layers on top of it. We find that good results are obtained with repetitions of 5 minute immersions followed by 20-30 minute oxidation periods.
Depending on the state of the indigo dark shades can be obtained by repeating the immersion-oxidation process up to 10-15 times.
Other natural dyes
We extract natural dyes from a variety of natural sources. Currently we work mainly with sappanwood, mangosteen skins, pomegranate skins, eucalyptus leaves, lac, coffee, myrobalan (as a source of both colour and tannic acid which will be explained shortly) and barks of various domestic woods. We also collect onion skins from a family member's restaurant for the lovely golden brown shade that they yield under certain conditions. The dye is extracted by simmering the dyestuff in water for several hours.
Because the majority of natural dyes do not readily attach themselves to fibre in the same way that indigo does they require a very different process that involves the use of metallic salts otherwise known as mordants. When fibre is treated with a mordant it allows for a relatively strong bond to take place between itself and the dye molecule. Without it the dye will not be taken up properly and will likely wash out or fade away. The two mordants that we use to treat fibre before dyeing it in natural dyes are potassium alum and ferrous sulphate which are known for their relatively low toxicity.
An important point to consider regarding cellulose fibres is that the mordant will not bond to them especially well unless the fibre has first been treated with tannic acid. This means that when dyeing cotton, linen or hemp in natural dyes the best results are obtained with a three-step-process: an immersion of the fibre in a simmering bath of tannic acid (which readies it for bonding with the mordant) followed by an immersion in a mordant solution (which readies it for bonding with the actual dye molecule) and finally the immersion of the fibre in a simmering dye-bath. Although different from indigo dyeing both processes share an important principle: slower is better. For best results the fibre should ideally be left to steep in each of the three baths overnight, adding a total of three days to the entire process.
Infinite variations exist and intricate combinations of shapes and colours can be achieved by over-dyeing natural dyes with indigo, utilizing multiple dye-baths, mixing the two mordants at various concentrations, applying the mordants directly to the fabric in a thickened form instead of dissolving them in water, adding more stitch-resist threads to the cloth bundle in-between applications of several dyes and altering the PH level of the dye-bath which will change the hue of certain colours.
When a satisfactory result is achieved at this stage we can then move on to the next step.
7. Thread cutting
Each of the individual threads that hold the compressed cloth bundle together now need to be cut so that the cloth can fold back out. Extra care needs to be taken as the fabric tends to be dark and wet at this point, making it easy to inadvertently cut the fabric itself instead of the threads. If all goes well then the fabric will begin to unfold and reveal the pattern that has been created. It is then washed, dried and the dye-job is considered finished.
There are instances where pattern overlay is required (for example: a set of horizontal lines that cross a set of vertical lines, or colour/pattern blending combinations that cannot be achieved with one compression alone). If this is the case then we repeat the process beginning from step 3 by once again plotting a template for the new overlaying pattern, stitching, pulling, dyeing and thread cutting to get the result that we want.
8. Disposal of leftover dye
As the substances involved in this process are relatively harmless we simply use any leftover liquid to water our garden. Occasionally high PH levels may need to be neutralized with vinegar.
Some materials (like onion skins) can be quite difficult to obtain in large amounts and so to make the most use of the extracted pigment we make what is typically called a “lake” by adding potassium alum and soda ash directly to the exhausted dye-bath. The alum bonds to any remaining pigment molecules and transforms into an insoluble state in an alkaline solution. The alum-pigment molecule then very slowly sinks and collects at the bottom of the container. The liquid on top of the accumulated pigment is siphoned off, fresh water is poured back into the container and the pigment is allowed to sink and gather at the bottom once again. By repeating this process we can obtain a very pure and concentrated pigment that is free from impurities. This typically takes three to four days, at the end of which the accumulated pigment is filtered through a coffee filter, dried and stored in an air-tight container. In this form it can be mixed with a binder and used for watercolour painting or applied as a wall plaster. We are currently working on applications that involve brushing this highly concentrated pigment through stencils onto fabric to create finely detailed designs.