Article published in Printmaking Today
Print - making it real
When was the last time you heard a sculptor or painter saying that they were going into the studio to do a bit of 'sculpture-making' or 'painting-making'? The 'making' of prints underlines the close relationship between the technical and the creative act of printmaking. Indeed, one of its many attractions as a discipline is the wide range of techniques it offers to artists.
Throughout its history, printmaking has been open not only to the remediation of technologies in the service of the creative idea, but has also, from within its own practice, inspired new forms of technology. Photography, for example, drew on experiments with lithography. Where would we be without CYMK, four colour reproduction as developed from the 18th century mezzotint techniques of Le Blon and 19th century colour woodblock printing? Printmaking has a fascinating genealogy of remediation, full of historical affiliations and resonances.
Printmaking and engineering
I identified that a Computer Numerically Controlled (CNC) machine would offer possibilities in the making of a printing plate. The base concept of CNC process modelling is that a computer program controls a cutting tool head. It is a computer - programmed digital routing tool.
I collaborated with The Northern Ireland Technology Centre (NITC), which is part of Queen's University of Belfast, N. Ireland. The two CNC machines at NITC are a VMC100, 22 Digital and a VCM 600, 22 and both offer a smooth technological flow between the design and machined plate. The design and management team at NITC are Tom Edgar, Director, Robert Seaman, Manager and James Knox, Head of the Engineering Department. It was interesting and refreshing to collaborate with engineers - 'Why do you want a squiggle line? as an artist I had to justify my work. At first we spoke in two different languages, but gradually we developed a common language and terminology.
The cutting pattern of the CNC machine left a defined 'ribbing' or circular indentations on the surface of the plate though, with the introduction of a smaller routing head, this was kept to a minimum. I actually liked the effect and accepted the pattern as part of the plate. The main limitation of creating a CNC - machined plate is that a design has to take account of the constraints on the routing tool in changing direction on the plate; this had an influence on the overall design. However, the Queen's university CNC machine also had digital software called FeatureCam, which constructs a virtual design on the computer. Depths can be ascribed and the software is sophisticated enough to allow the design to be viewed from a variety of angles, before the final decision to route the metal is made. The illustrations here of the CNC - machined plate inked in colour, using the principles of Hayter's viscosity printmaking technique, give an indication of how colour distribution works across the CNC plate and of the path of the cutting tool.
Hayter documented the principles of viscosity printmaking in a highly scientific manner, and in my research, I was able to take advantage of his methodology to contrast and define the CNC practice framework. Viscosity printing is a unique method, based on tacit knowledge accumulated over many years of the inter- relationship between the etched plate, roller and colour interface. The CNC machined plates cannot replicate the arbitrary gestural marks of an etched plate. However what the CNC intervention does facilitate is:
- 1. The predetermination of colour areas through depth/nature of the CNC cut.
- 2. The opportunity to specify depth and width of line at the design stage.
- 3. The precision and control of the design routed on the plate.
- 4. The replication of that plate to another CNC facility anywhere in the world.
- 5. A CNC - machined plate facilitates the organization of colour distribution using selected principles of intaglio simultaneous colour printmaking.
Hayter's Viscosity Techniques
Stanley William Hayter, founder of the renowned Atelier17 workshop in Paris, France, invented viscosity printmaking in the 1940s. It followed his experiments with the application of surface colour to an intaglio printing plate in 1930 and, in collaboration with Anthony Gross, the further exploration of this method of 'simultaneous printing' from surface and intaglio inking in 1932. In 1940, after the German occupation of Paris, Hayter moved the workshop to New York, where he continued to investigate simultaneous multi-coloured printing.
The main principles of intaglio simultaneous colour printmaking are outlined in Hayter's book, New Ways of Gravure' (published in 1966).
'Thus perhaps a hard roller will carry a film of colour of low viscosity which will deposit only on the original unetched surface of the plate: a soft roller, carrying a colour of higher viscosity, will then surround these forms with a second colour, neither affecting the intaglio colour originally present in the plate which might appear between the two.'
The key point is that inks of different viscosity values (rate of flow) repel each other. 'High viscosity' indicates that the pigment is mixed with less linseed oil in relation to the other colours being used; 'Low viscosity' that the pigment has a high percentage of oil again in comparison to the other colours being used. Based on this principle, a multi-coloured inked plate may be printed through the press.
Other elements and principles that define this printing process are briefly:
- 1. The control of surface tension (of the film of colour)
- 2. The order of succession of colours.
- 3. Use of hard and soft rollers and pressure
- 4. The direction of rollers with colour over the plate.
Rheological Measurement
As part of the research I undertook a rheological study in collaboration with Mr. Damian Chandler at the Particle Analysis laboratory at Queens University. Rheology is the study of the change in form and flow of matter, embracing the measurement of viscosity. The purpose of the study was to determine and measure the point at which two inks of different viscosity values repel each other for the purpose of controlling colour distribution. The calibration of flow behaviour also served as a measure of colour consistency and provided a controlled constant, complimenting the controlled depth of the CNC machined printing plate and the constant of hard and soft printing rollers.
A knowledge of the rheological behaviour of printing inks of different viscosity values enables the formulation and prediction not only of colour separation but also of controlled colour merging over the CNC machined plate.
My preliminary research using CNC technology to control the depth and design of the plate marked the beginning of presenting a 'hybrid' CNC - mediated print. It was evident that the introduction of constants would substantiate and inform the research. These are the constants identified:
- 1. The printing roller 'shore' [a measurement of how hard or soft the rollers are] Those used in the final printing of the plates were 50 and 25 shore.
- 2. The size constraint of the VMC 1000,22, Digital CNC machine - which is 1000x600mm. [However, in consultation with the engineer, 500 x 400mm was selected as the plate had to be clamped down during routing. This was also the size of the bed of the press on which the cut plate would be printed.]
- 3. The gauge of the metal - 3mm gauge was chosen, as this was suitable both for the printing press and the CNC machine.
- 4. Pressure of the printing press.
- 5. Use of the same metal - brass.
Various metals were cut, including copper, steel, zinc and brass [also - out of sheer curiosity - lino] to identify which was the most appropriate for the CNC process.
Test pieces embracing the constant factors referred to above were made to identify the depths of cut most appropriate for viscosity printing.
Conclusion
My research over the last three years has involved the remediation of Hayter's viscosity printing by the integration of CNC digital technology towards a practice framework for artists wishing to incorporate CNC technology.
The CNC technology has enabled me to predetermine the depth and design of the plate by virtual proofing in FreeCam before the plate has been manufactured.
The rheological study of the measurement of printmaking inks with different viscosity values enabled both the formulation and prediction of colour separation and also controlled colour merging over the CNC machined plate. The convergence of these two aspects of the research has led to a greater control over the design and colour outcome of a simultaneous coloured intaglio plate.
Bibliography
- Black, P. Moorhead, D.& Kane, J. The Prints of Stanley William Hayter; A Complete Catalogue. 1992, Phaidon Press Ltd., London.
- Bolter, J. & Grusin, R. Remediation - Understanding New Media. 2000, MIT Press.
- Hayter, S.W. New Ways of Gravure. 1966, 2nd Edition, Oxford University Press, London.
- Lin, S.C., Chen, C. & YU-PU,Y. CNC Process Modelling Using SmartCAM. 1995, Scholars International Publishing Corp.
- Ready, K. Intaglio Simultaneous Colour Printmaking - significance of materials and processes. 1988, State University of New York, Albany.