Monday, November 10, 2014

Woodcut printmaking - Letterpress Commons

Woodcut printmaking - Letterpress Commons

Woodcut

Woodcuts are relief printing plates made by carving marks in blocks of long grained planks or plywood. Long-grain refers to the grain following the direction of growth, i.e, parallel to the tree trunk/branch the piece of wood was cut from.

Woodcuts vs. Wood Engravings

While both are relief printing methods, Woodcuts are distinguished from wood engravings by both the grain direction of the wood used and the tools employed. Wood engravings are typically made in hardwood blocks cut across the grain or endgrained, that is, perpendicular to the growth of the tree using gravers and scorping tools. Woodcuts are made in wood plank or plywood with the grain parallel to the direction of growth using knives, gouges and chisels.

Carving Tools

The tools most typically employed to make woodcuts are carving gouges of various shapes and sizes along with various chisels and knives. There is a wide variation in construction and quality of carving tools. Personal preference and style of carving will ultimately have the greatest impact on the types of tools employed, however, it is paramount that the tools be of good quality and kept sharp.
Fewer tools of higher quality are preferable to a large selection of tools of inferior quality. A small and large u-gouge, a small v-gouge for details, a knife for outlining and a wide gouge for clearing areas is a good selection for the beginner.

Types of Wood

Wood used for a woodcut must be clean, well seasoned or kiln dried, and perfectly flat in all directions. Many types of wood are suitable, both hardwoods and softwoods may be utilized depending on the amount of detail required. Certain soft woods, such as some species of pine, cedar or cypress, may not allow details to be successfully rendered and may also compress during the printing process but may still yield interesting results. Hardwoods such as mahogany, poplar, ash, birch, apple or cherry plywood are more difficult to carve and require more attention to tool sharpening but retain smaller details and hold up to printing pressure and abrasion better.

Blocks of wood used for woodcuts

David Black

Cedar Paneling, Shina Plywood and Pine Plank (top to bottom) are suitable for making woodcuts. It should be noted these are all less than .918 in thickness and will need to be shimmed before printing.

Plywood made from birch, cherry, and fir is widely employed as it has a more predictable and consistent thickness, surface quality and more is easily acquired than suitable planks. Plywood should be flat, clean, free of internal voids or knots that may affect impression and checks or cracks that may damage rollers. Plywood is typically graded with a lettering system: A being the high grade and D being low grade. Two letters are commonly listed, (sometimes a third added to indicate the intended exposure rating) with each letter indicating a face. For example, AA graded plywood would be plywood with two clear faces and few voids. AC plywood is the most common and would indicate a clear face and a face with some imperfections and filled knots or voids. Voids in the internal structure of the plywood block may affect impression. AA or higher grades of plywood will have the fewest voids.

Buying wood directly from a well stocked lumber yard that serves fine woodworkers rather than one of the box store retailers will yield higher quality and more selection of interesting species. Lumber yards also often offer some milling services, so you may be able to have stock panels or planks accurately milled to desired dimensions and occasionally thicknesses as well.

Buying small samples of various species and performing some tests is ultimately the best way to determine which wood products will yield the desired results.

Testing a wood block for woodcuts

David Black

Any wood may be tested for suitability by making various tool marks and noting the results. In this instance, a small section of Pine plank has been tested and then inked in black to give better contrast to the results.

Preparing Wood for carving

Since wood reacts to the humidity of the environment by expanding and contracting, it is advisable to purchase planks several weeks in advance and allow them to acclimate to the studio norms of humidity and temperature prior to carving. Store them well supported and flat with adequate air circulation. This can assist in preventing distortions in the surface and relieve internal stresses in the materials that may build up when moving abruptly from high humidity to low humidity or vice versa. Generally, if materials are purchased locally during the spring and summer, this is not an issue as the climate inside the studio should be close to those found in the lumberyard. This is not always true in the winter or fall when a damp, cool plank is brought into a warm dry studio. A large section of one surface carved away will shortly begin to bend and/or twist in response.

Plywood, with its veneers of alternating grain direction is not quite as susceptible to these stresses, but should still be given some time to acclimate and can warp if stored on end, or if one side becomes dampened.

Warping, cupping, and other distortions can be mitigated with sanding, planing, and careful reintroduction of moisture. However, wood already demonstrating these issues should be passed on if other sources are available.

Once the desired size block and been gotten out of a plank or panel, it should be lightly sanded using medium to fine sandpaper mounted on a sanding block to remove any proud standing burrs, irregularities, loose materials, or splinters on the face. If the edges of the block are rounded or eased they will print as a soft or fuzzy edge. Unless this is a desired effect, care should be taken during sanding to prevent the sanding block from sliding over the edge at anything other than right angles.

Once the surface has been uniformly cleaned, a cloth lightly dampened with alcohol can be used to remove sanding dust. Any liquids, including mineral spirits, can swell or "raise" the grain of the wood. You may use a cloth lightly dampened with water to exaggerate the grain, taking care to allow for complete drying.

Transferring the Image

Direct Drawing

The most simple method of preparing an image on the woodblock is to draw directly on the wood surface with pencil or marker, bearing in mind the resulting image will be reversed when printed. No materials other than a pencil or marker are required for this method. Care should be taken to only apply enough pressure to make a readable mark and not crush the wood grain or surface as this may show up as undesired errant marks during printing.

Transfer or Carbon Paper

Designs may also be transferred using transfer paper or carbon paper sandwiched face down between the drawing and the wood surface with a ballpoint pen or other stylus used to trace the drawing. The resulting pressure will transfer a copy in carbon/graphite to the surface. Care must be taken to prevent crushing or indenting the woodgrain; experiment to find just the right amount of pressure to make a transferred line without indenting the surface.

The drawing to be traced should be reversed rather than right reading. The resulting line transfer should be re-traced with a Sharpie or other marker if you intend to proof your image frequently while carving, otherwise it may wipe off when exposed to ink. Materials required for this method are transfer paper and a copy of your image, reversed and sized in proportion to the block.

You may also simply shade the back side of the paper your image is drawn on with a thick layer of soft graphite pencil, so it may be used as transfer paper would. Clarity of the transferred image may be variable, however.

Toner Transfer

The toner transfer method is technically complicated, but yields very fidelitous results—important if the image has a high level of detail. This technique of image transfer to the block requires the use of a heated transfer tool, a photocopy, and mineral spirits. The image should be transferred before the wood surface is sealed with varnish (see preparing the wood surface earlier in this section) and then the surface should only be sealed with a waterborne acrylic, as shellac may loosen the transferred toner and blur the image.

This method should only be used in a properly ventilated and fire safe environment. The transfer tool is hot enough to cause severe burns and must be kept under observation during use. Mineral spirits are flammable and should be stored and applied in an area away from where the transfer tool is to be used for the procedure.

Materials needed:

  • Heat transfer tool not greater than 18w capacity. These are available widely in stores selling wood carving tools and most craft stores. Higher wattage tools will scorch the wood immediately and cannot be used.
  • Odorless Mineral Spirits
  • Photocopy made on a non-fusing oil or dry toner type copier of the 'right reading' and properly sized image for the intended block. The fresher the copy the easier the toner will transfer.
woodcut transfer tools

David Black

Materials needed for heat transfer of image to block.

Steps:

  1. Photocopy is placed face down, aligned properly, and secured to the wood block with tape.
  2. Plug in the transfer tool and allow it to heat up to operating temperature. (5-10 min)
  3. A cotton ball, cotton makeup applicator, or clean cloth is wetted with a small amount of odorless mineral spirits and rubbed over the entire image area of the photocopy until the paper is just wetted enough to be translucent, but no liquid is apparent.
  4. The fully heated transfer tool is worked over the paper surface in the image area. Wisps of pale smoke may rise from the surface. Keep the tool firmly and flatly pressed to the surface and constantly moving. The paper should dry, become opaque again, and stiffen as you work; this is a good indication that you have heated the area adequately. If the paper begins to discolor you have overheated that area.
  5. Continue working until the image is completely transferred.

Note: Pausing in one area may cause scorching, keep tool in constant motion. Tool will cool during the image transfer process, working methodically in small areas with occasional pauses to allow the tool to recover proper operating temperature will give the best results.

Sealing the Block

The wood surface can be sealed with Shellac (alcohol based) or Waterbourne Acrylic Varnish to allow for better ink release and to help prevent surface splintering of softwoods during carving. Avoid using sealants or varnishes that are oil based as the inks and solvents can soften them during printing or cleaning with disastrous results.

Wood may be printed without sealing the surface, however the ink used during printing will soak into the surface somewhat rather than release onto the paper. This affects the density of solids until the pores have been filled and can be frustrating. The wood surface will also swell and soften a small amount. Sealing the surface prevents this from occurring and allows for more carefree handling during printing.

Apply one or two thin coats of Shellac or Acrylic Varnish, lightly sanding between or after each coat. Careful application is important; drips, brush marks, stray bugs and other imperfections will reproduce in the print. Only enough varnish is needed to seal the pores of the wood and toughen the wood surface. Coating both sides at once and drying raised on thumbtacks prevents warping.

Acrylic varnish will significantly raise the grain as the water contained in the vehicle readily soaks into the wood. The effect is not as pronounced with Shellac.

Check to be sure you've coated the surface uniformly, as any areas of uneven application may show up as changes in ink density due to absorption.

Carving the Block

Success in carving wood blocks can depend heavily not just on skill, but on the quality and sharpness of the tools employed. As mentioned earlier in the is section, a few sharp, good quality tools are preferable to a large selection of inexpensive tools that do not hold a sharp edge.

Frequent honing while carving allows you to avoid longer and more difficult sharpening sessions.

Wood, as an organic material, has a great deal of variation in reaction and behavior when carved. Cutting across the grain can cause splintering. Occasionally the grain can cause tools to wander if care is not taken to maintain a sharp edge and an even, moderate application of pressure while working.

There are many different techniques employed for the actual carving of the image; the following illustrates a typical approach as used on Shina Plywood.

Prior to starting work, a small amount of transparent printing ink is rubbed into the surface to stain the surface. This will assist in judging the development of the image. As material is removed, the unstained wood underneath will contrast with the surface material which is stained. Red or light blue are good choices. Waterbased ink should be avoided as the grain will swell. Alcohol based markers may also be used.

1. Careful outlining of the image can be performed with a v-gouge, angled knife, or heavy utility blade. Leaving a small margin around the actual image allows for later refinement. The raised area left behind should be supported by a sloping edge rather than an abrupt straight angle for support and stability. Note: A small section of reglet, steel, or brass bullnose rule held behind the cutting edge of the tool protects the wood's surface by preventing unintended crushing of the surface from the backside of the tool.

2. Further refinement of the image.

3. Open areas are cleared with a large (in relation to the size of the block) u-gouge. In many cases only ?" deep or less material removal is needed to allow for clean printing. A smoothly cleared surface is preferable to a rough one as it is less likely to snag cleaning rags or hide stray printing areas.

4. The block may be proofed carefully and further refined as needed.

The finished block needs to be carefully inspected for loose splinters, raised sections or other debris that may damage rollers. Gentle poking and careful inspection of small raised details to check for soundness is also advisable.

Printing the Block

Once the image has been carved, the block needs to be shimmed to proper height for printing. Binder's board, masonite, MDF, additional plywood blocks or chipboard alone or in combination may be employed for this.

Type high gauge in use

David Black

Checking the block is the proper height with a type high gauge. This one has turned out a little high and will need some underlay removed.

When printing the woodblock, carefully build up the underlay until the block prints evenly and densely. Heavy impression will crush most woods except for the toughest hardwood (and difficult to carve) species. Start with a light impression and add underlay slowly and carefully.

The block should be given close attention during the print run with careful appraisal of it's condition. Wood is an organic material and may show unexpected reactions or wear during the run. It is better to catch something like a small section of detail coming free before it does, than to fish it out of the inking rollers.

The block should be cleaned with a gentle dry wipe with a sturdy cotton cloth. Alternatively, a cloth dampened with a small amount of solvent may be used. Non-drying oils, water-miscible solvents and even mineral spirits can swell and soften the woodcut, breaking free small details or changing the surface's reaction to ink. Solvent, if used, should be used as sparingly as possible.

Blocks should be stored flat, the surface protected, in an area with controlled temperature and humidity to prevent warping or other distortion.


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