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Growing Your Own Ink Mordants Mordants, are a range of chemicals, some as old as dyeing itself, which when added to the plant colourant have the effect of modifying or even transforming it completely. When testing for colour content I place a small amount of these mordants each in a separate section of an indented mixing palette. Then I add a measured amount of the plant colour to each section and paint a swatch of the resultant colour onto a pre-printed test card. The chemistry of what occurs to cause these colour changes is beyond the scope of this article. Unfortunately, it is an inescapable fact that not all the mordants are particularly benign; potassium dichromate (Cr), copper sulphate (Cu), and stannous chloride (Sn), are not the friendliest of chemical substances, but apart from a very few exceptions they are not essential for the production of an adequate range of colours. The point is that in textile dyeing the mordant performs two very distinct functions only one of which is necessary for our purposes. Firstly mordants actually make it possible for all but what are called ‘substantive’ dyes to fix molecularly to the fabric or yarn, so that it can resist the action of soap and hot water when washed. Secondly, they can cause those colour changes previously mentioned and it is only this effect which is of importance to the printmaker. So as long as we can obtain a satisfactory range of colour using the more familiar and less toxic substances like citric acid (Ca) (lemon juice), acetic acid (Aa) (vinegar), bicarbonate of soda (Bs) (for upset stomachs), or sodium carbonate (Sc) (washing soda) we remain substantially more environmentally friendly than any of the current water-based products. As to quantities, the recommended amount per measured quantity of colour depends entirely upon the specific hue required, though excessive amounts of iron (Fe) for instance might begin to damage the paper stock. In the tests, I added between 3% and 6% mordant (by weight) to the standard 2.5 ml. test measure. A full list of the mordants used in my tests is given below. Of course there is no need to use mordants at all if the colours do not require modification but their use significantly increases the plants’ colour potential. Key to Mordant test sheet SC - tin (SnCl4
stannous chIoride) Thickeners Because screen printing itself dates from the early part of the 20th century the first patent being applied for in 1907 by Samuel Simon, a Manchester businessman (Faine,1989), its introduction virtually coincided with the final demise of vegetable colours. Fortunately however, textile screenprinters still use a number of traditional vegetable thickeners (even for use with synthetic colours) and these include rice starch, potato starch, locust bean, seaweed (sodium alginate) as well as the gums Arabic, Karaya and Tragacanth which can be combined with vegetable oils to achieve more flexibility (Taussig,1947). Honey, glycerol, glucose and molasses are also useful retardants (Middleton,1936/1960). I found potato starch ideal for thickening, and this can be obtained from a variety of textile suppliers, I got mine from Hays Colours 55/57 Glengall Road, London SE15 6NQ who also supply a range of other thickeners. Light fastness Much has been said about the inferiority of vegetable colourants with regard to light fastness, and some colours are highly fugitive, Beetroot and Red Cabbage suffer from this drawback. In the main though this reputation is both unfair and exaggerated. The fact is that quite a number of traditional pigments are far from permanent - ask any picture restorer about chrome yellow, vermilion or Vandyke brown. I must admit though that I have not tested all my samples for light fastness yet, though the ones I suggest in this article are fair to excellent in this regard.
Phil Shaw MA(RCA)
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