Project Summary: Digital Woodcut This is a collabora,ve project between printmaker Beth Howe and a digital ar,st Clive McCarthy that fuses contemporary digital technology with tradi,onal relief prin,ng technology. McCarthy has wri@en a customized code to process imagery developed by Howe and McCarthy together. The resul,ng images are cut into relief woodcuts using a CNC milling machine, and finally printed on the etching press. Triumphal Arch (Class II), 8F x 12F, was printed at Banff in June/July 2012.
Project Descrip7on: In the course of sharing with each other our current projects, Clive showed Beth the results of code he was wri,ng that rendered photographs into images built of lines of varying width. The result creates an illusion of grayscale akin to tradi,onal engraving techniques. Beth wondered if we couldn’t output Clive’s process to a ‘real’ material (such as wood) to be printed onto paper on the press. We opted for a CNC router and, aFer experimenta,on and tes,ng, developed code that bypassed intermediary soFware chains and translated Clive’s process directly into G-‐code, the language of the router. By wri,ng our own code we can make choices about what kind of markmaking we want the machine to cut, such as modifying the angle of the lines and their ‘wobble’ (that is, we can make them non-‐parallel). For this project we wanted to take sugges,on from the history of the medium – especially North American engraving from the 19th century -‐ and work with landscape. The landscapes of the West changed substan,ally since that age of territorial expansion and the 20th century freeway has become a ubiquitous and at ,mes elegant feature of the Western landscape. We wanted to work large in order to evoke the monumentality of the architectural landscape we are depic,ng (built of nine 30”x44” ,les, Triumphal Arch (Class II) is roughly 8F x 12 F). By working large, we can also take advantage of the way the image moves between abstracted marks at close range and comes together as a more seamless image from a distance. The ,tle comes from realizing during the course of the project that Durer’s monumental woodcut ‘ Triumphal Arch for Maximilian I’ is of similar dimension and that the sec,on of freeway we photographed in San Francisco was recognized by the American Ins,tute of Steel Construc,on with its ‘Annual Award of Merit -‐ Most Beau,ful Steel Bridge Class II’ in 1955.
The Process
Original digital image
‘Simulacra’ of the cut block
1. Star,ng with a digital photo of similar aspect ra,o to the intended paper size, Clive processes the image and generates G-‐code cubng instruc,ons for the CNC milling machine as well as a ‘simulacra’ image, which gives a sense of what the printed image would look like.
The code does the following: • Scales and crops the image to conform to the overall size of the work based on the paper size, number of sheets of paper, bleed, ma@e & framing. • Modifies the grayscale range so that no areas are en,rely black or en,rely white (though this can be changed if we decide we do in fact want areas to go to clean white or solid black). • Takes input for line pitch, varia,on on line angle and line ‘wobble’, or non-‐parallel-‐ness. • Flips the image so that it will cut a reversed image on the block that will then be right-‐reading once printed to paper. • Crops the image into a series of sub-‐images, one for each sheet of paper, accoun,ng for the ma@e etc. • Evaluates the grayscale values along the cut line in the image and assigns a cubng depth based on how ‘white’ or ‘black’ the area is. The deeper the cut, the more material is removed from the plate and the more ‘white’ the area appears. • Issues an appropriate G-‐code instruc,on for the CNC machine.
Sample piece of G-‐code generated for cu=ng this image: N100 G40 G54 G80 G90 G94 (safety block) N110 T1M6 (Tool: 60.0 degree conical mill with a 0.000 inch diameter ,p) N120 M03 S15000; (spin clockwise at 15,000 RPM) N130 G20 (inch mode) N140 G17 (xy plane selec,on) N150 G00 X0.0 Y0.0 Z1.0; (go to the origin) (intaglio cut #1) G00 X0.000 Y0.380 Z0.100 G01 X0.000 Y0.340 Z-‐0.203 F60 G01 X0.010 Y0.290 Z-‐0.201 G01 X0.020 Y0.240 G01 X0.040 Y0.190 Z-‐0.205 G01 X0.060 Y0.140 Z-‐0.199 G01 X0.070 Y0.090 Z-‐0.183 G01 X0.090 Y0.040 Z-‐0.192 G00 Z0.10 (9 blocks) (intaglio cut #2) G00 X0.000 Y1.420 Z0.100 G01 X0.010 Y1.390 Z-‐0.273 F60 G01 X0.020 Y1.340 Z-‐0.260 G01 X0.040 Y1.290 Z-‐0.254 G01 X0.060 Y1.240 Z-‐0.210 G01 X0.070 Y1.190 Z-‐0.197 G01 X0.090 Y1.140 G01 X0.110 Y1.090 Z-‐0.203 G01 X0.120 Y1.040 Z-‐0.197 G01 X0.140 Y0.990 Z-‐0.238 G01 X0.160 Y0.940 Z-‐0.230 G01 X0.170 Y0.890 Z-‐0.249 G01 X0.190 Y0.840 Z-‐0.260 G01 X0.210 Y0.790 Z-‐0.183 G01 X0.220 Y0.740 Z-‐0.189 G01 X0.240 Y0.690 Z-‐0.197 G01 X0.260 Y0.640 Z-‐0.187 G01 X0.270 Y0.590 Z-‐0.196 G01 X0.290 Y0.540 Z-‐0.205 G01 X0.310 Y0.490 …
CNC milling of an early test of linoleum mounted MDF.
2. The G-‐code is sent to the CNC milling machine and executed on ½” MDF panels. Each 30x44 panel took a li@le less than 1 hour to cut.
3. The freshly cut MDF plates are prepared for prin,ng by removing milling dust.
And then the MDF panels are sealed with polyurethane.
4. AFer they are dry, the plates are rolled up with relief ink and printed onto co@on rag paper one at a ,me on an etching press.
Detail of inked woodcut block
Cleaning out small imperfec,ons Plate on press ready to print (leF) Running the plate through the etching press
Freshly pulled print on the drying rack
Details of printed marks
Triumphal Arch (Class II), 2012
Next steps: We will be working together to further develop our process, adding new code-‐generated mark-‐making styles to our vocabulary to translate to tradi,onal printmaking matrices (i.e. small hatch marks, or highly irregular lines, or dots). We would like to move away from direct reference to historical engraving-‐like marks to create marks that are at once machine-‐like and much more organic than straight lines: in effect, we are trying to create expressive mark-‐making through the code and use the hand only in the manufacture of the prints. Because G-‐code is used for other machine tools, such as lasercu@ers, we would like to experiment with using different cubng tools and different substrates. We would like to cut an embroidery-‐sampler-‐style collec,on of half a dozen different ‘marks’ into plates of wood, metal, plas,c, etc. Then we will have a larger pale@e of marks to choose from as we pursue future subject ma@ers.