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Sunday, 8 September 2013
Ruth Brown Cyanotype Prints
My thanks to Ann Pocklington for putting together her impressions of the workshop held at the 20:21 Gallery in Scunthorpe on Saturday 17th August 2013. This was a really enjoyable workshop lead by Ruth Brown, experimenting with the photographic (not dyeing) process of cyanotyping. Fabric choice The process needs a natural fabric and the choice will affect the results. Cotton works well, as does silk vicose velvet. Silk noile has silk gum, sericin, in it which resists the chemicals used and gives a spotted result. Woven viscose gives a textured result and spun rayon gives a very crisp image. Although these last two are man-made fabrics, they are made from plant cellulose, so react as natural fibres. Applying the chemicals Ruth showed us how to frame up our natural fibre fabric to paint on the light reactive chemical mixture with a wide brush known as a hake. A brush without a metal band is ideal, as metal will react with the mixture. The fabric doesn’t need stretching taught, just tight enough to stop it touching the work surface below the frame. The chemical mixture consisted of equal volumes of of ferric ammonium citrate (25 grams per 100 cm3 water), mixed with potassium ferricyanide (10 grams of per 100 cm3 water). These solutions will deteriorate over time when mixed, but will keep for about three months if kept separately at a constant, cool temperature in the dark. The mixture is used to moisten, not soak, the framed fabric, avoiding the wood and wiping off any spills with bleach. Different ways of applying the mixture will affect the result, for example using a sponge, a dry brush or spritzing the mixture will give a textured image. Drying The fabric was left to dry. As the reaction to develop the colour needs ultra-violet (UV) light, this can be done in normal daylight or artificial light as long as there is no direct sunlight. Printing Between us we used a variety of objects including ferns, flowers, seed heads, grasses, lace, cut out letters, buttons, chains, and peel offs. The objects were placed on the fabric and left to develop under a sun bed until the fabric turned grey (green-grey on silk). A facial solarium or very bright sunlight will work. Fragile objects like feathers can be flattened under a sheet of glass - most glass does not stop all UV light, but will reduce the amount reaching the fabric, and some glass - eg. glass made for conservatory window panes -is designed to really reduce the amount going through. Another way of flattening objects is by sticking them onto clear sticky backed plastic. We had two rolls to choose from – and to Ruth’s surprise one completely blocked UV and gave no results. The moral is try any material used to flatten objects before going ahead. I was particularly keen to try the effects of using a digital image and I was absolutely delighted with the result. I had already chosen a photograph and scanned it into my computer. I turned it into a greyscale image and increased the contrast in a fairly heavy handed way before resizing it to print it onto the rough side of an inkjet compatible acetate. Ruth advised us to print not at the ‘best photo’ or ‘transparency’ settings, but to use normal glossy paper setting. The acetate can be fixed to the fabric by using a temporary adhesive spray such as 505, Other ways of altering the light reaching the fabric are by laying bubble wrap over it, letting the sunlight be defracted by a shallow cut glass bowl or scrunching the fabric – perhaps scrunching, flattening and rescrunching during the developing time. Rinsing When the colour of the fabric had developed, the pieces were well rinsed. A few drops of hydrogen peroxide added to the rinse water speeded up the development of the blue colour and this was rinsed out before continuing. Preserving the cyanotype When thoroughly rinsed, the cyanotype can be dried. To preserve it, avoid rubbing, iron on the back, and keep it out of strong UV light. Wash it if necessary in products designed for wool or silk. Keep it away from alkalis which will turn it yellow. Other colour effects The colour can be deliberately changed with the use of alkali to give a yellow tinge. Strong tea will produce a sepia tint, while pure tannin will give a reddish brown. The fabric can be procion dyed or steam fix silk dyed before cyanotyping. As cyanotype colour is translucent it acts as a glaze and the underdying shows through. Alternatively, the finished print can be overdyed with steam fixed silk dyes or heat set silk paints. The positioning of these can be controlled by using an outliner such a gutta to restrict the overdying to only parts of the cyanotype. Health warnings Use rubber gloves and a face mask if you are sensitive to the chemicals used. UV light in any form can harm cells and is potentially carcenogenic. Follow the safety instructions that apply to any light source you use. Hydrogen peroxide is one of the strongest known oxidising agents and should be used in dilute concentrations and with caution. The fact that it is used to decompose dead tissue around wounds should give a clue as to the importance of following instructions on the container in which you buy it! Ann Pocklington