No-Fear VeneeringComments (0)
This article is from Issue 37 of Woodcraft Magazine.
Give your work a beautiful skin.
By Jonathan Benson
Veneering has been around since the age of the Pharaohs and has been used to create some of the finest furniture ever made. Applying a decorative “skin” of wood veneer to an underlying substrate can beautify mundane wood panels and stretch the use of rare, exotic, and expensive woods, many of which are difficult or impossible to find in lumber form these days. Another advantage is that, when properly glued to a sound substrate, veneer is very stable and not subject to seasonal expansion and contraction. Therefore, it can be arranged in any pattern or combination of species without danger of cracking or splitting. Many veneers are sliced in sequence from a log in closely matched sheets, allowing arrangement of many symmetrical or repeating patterns.
To the uninitiated, veneering can seem intimidating and complicated. But not to fear; I’ll explain the basic tools and techniques that you need to get started. Then, as an exercise, I’ll walk you through the steps for creating a “four-way” match, like the one used to make the box top on page 48 (see “Curved Top Box”).
Choosing and storing veneer
Veneer is available in a wide variety of species, figures, and sizes, in thicknesses ranging from 1⁄20" to 1⁄42" as shown in Photo A. The two common methods for producing veneer are rotary- and flitch-cutting. Rotary-cut veneer is made by pressing a long knife against a spinning log to peel away long, wide, continuous sheets, like those you commonly see on the faces of construction-grade plywood. Flitch-cut veneer is produced by knifing tangentially through the log in sequence, essentially slicing it into a stack of paper. This produces a series of closely matched sheets that you can arrange to create a variety of patterns like those shown in Photo B below. The bundle of sequentially matched veneers is called a flitch. I use flitch-cut veneers exclusively, as rotary-cutting doesn’t offer the same design possibilities.
As you start accumulating bundles of flitch-cut veneers, you’ll want to keep them organized and in good shape. Make sure to store them flat. If shipped in rolled form, let the sheets slowly relax, then number flitch-cut veneers sequentially to keep them in order. Wrap tape around the “end-grain” edges of each sheet to keep them from splitting. Highly figured veneers can be wavy and bumpy, and will need to be flattened before application to prevent cracking. (See “Flattening Veneers,” right.)
Substrates and adhesives
Common substrate materials include MDF, cabinet-grade particleboard, or high-quality plywood such as Italian poplar or Baltic birch. Bending plywood is useful for creating curved panels. Whatever substrate you choose should have a stable core and a smooth surface free of voids, bumps, and other irregularities. Avoid regular particleboard and other common building materials like construction-grade plywood. I also steer away from solid lumber as a substrate because of its seasonal wood movement.
Urea-formaldehyde (plastic resin) glue is one of the best adhesives for veneering, because it provides a long open time and dries very hard. However, it has to be mixed, and some health risks are associated with it. For many projects, I use polyvinyl acetate (PVA) or “yellow” glues like Titebond II and III. Both resist moisture, dry relatively hard, and suffer negligible “creep” over time. Titebond II can set up very quickly but is fine for smaller projects, while Titebond III allows longer open time for gluing up larger pieces. Other good choices include epoxy and Titebond Cold Press for Veneering. (I avoid contact cement, because the bond is unreliable.)
To prevent buckling and cracking, burl and other lumpy veneers must be softened with a flattening agent and pressed before use. Commercial softeners work well, or you can brew your own concoction from two parts white PVA glue, one part glycerin, one part alcohol, and three-to-four parts water.
Using a spray bottle or paint brush, soak both sides of the veneers. Repeat the process to keep them wet for a half hour. Then stack several sheets together, separating each with a few sheets of ink-free newsprint (available at art supply stores). Place the stack between plywood panels and apply light pressure. After 30 minutes, replace the newsprint. Change the paper every hour or two for eight hours, increasing the stack pressure as you go. Then maintain the pressure overnight.
These examples of four-way matches were all made using squares of macassar ebony veneer.
Tools and tapes
Veneering requires minimal gear (Photo C). Layout tools should include a drafting triangle for marking out square cuts and a protractor for laying out wedge-shaped matches. Scissors will rough-cut single sheets of veneer, while a veneer saw guided by a hardwood straightedge allows accurate cutting of several sheets at a time. I use knives for inlay and other intricate work. Shop-made sanding sticks (80 and 120 grit) are needed to shoot straight veneer seams, and a scraper will clean tape and glue from the veneered surface.
For cleaner sawing, I suggest modifying a standard veneer saw as shown in Photo D. Don’t bevel the “underside,” which rides against a straightedge when cutting.
For joining veneers, I use two types of tape: blue painter’s tape and white veneer tape. The blue tape, which removes easily without leaving residue, is for temporarily attaching pieces during pattern matching. The paper veneer tape (sold by most veneer suppliers) is used for final attachment at the seams. It has water-activated glue on one side, making it easy to apply and remove without damaging the veneer. Immediately after applying the tape, dry it quickly with an iron, which also prevents excess moisture from swelling the wood fibers. Veneer tape is available either with holes to allow you to see the underlying seam or without holes for additional strength.
Gluing and clamping
To apply veneer to a substrate, first make sure to remove any blue tape from the underside of the veneer (having used it to temporarily align the pieces during layup). Then use a brush or short-nap paint roller to apply glue to the substrate (Photo E). Thoroughly coat the surface without soaking it. (Too much glue causes lumps, while a glue-starved surface can result in sections of the veneer lifting.) Press the dry veneer sheet onto the glued surface, and then immediately dampen it with distilled water to prevent curling. Wrap the edge of the assembly with blue tape to prevent shifting, and then cover the veneer with newsprint in preparation for clamping.
Cover the faces of the glued-up panel with newsprint; then clamp the assembly between 3⁄4"-thick MDF platens, using cauls to distribute clamping pressure.
Methods for clamping, or pressing, the veneer to the substrate include vacuum clamping, screw-press clamping, and caul clamping. A vacuum press is a bag attached to a pump that evacuates the air from the bag to allow 14.7 pounds per square foot of atmospheric pressure to press the veneer in place. This method is ideal for curved work. A screw-press applies pressure from above via clamping screws attached to an overhead frame. For smaller jobs, you can clamp the work between MDF platens, using long wooden cauls to spread pressure across the panel, as shown in Photo F.
To ensure a good glue bond, leave the assembly clamped up for at least two hours.
After the glue has dried, remove the veneer tape and scrape away any excess glue before sanding the surface. To remove the tape, spritz it with distilled water and let it sit for a few minutes before peeling away the softened tape with a cabinet scraper (Photo G).
After the water evaporates, check the panel for “blisters” or other raised areas as described in “Fixing Veneer Blisters,” below. Make any needed repairs, and then scrape the entire surface of the panel with a sharp cabinet scraper to remove glue that may have squeezed through the veneer under clamping pressure. (Using sandpaper for this step risks cutting through the veneer.) After scraping, sand the surface with 220 grit before applying a finish. Surface-film finishes like lacquer, shellac, and varnish are good choices, because they overlay the veneer, unlike thin penetrating finishes like oils.
Fixing Veneer Blisters
In spite of your best efforts, “blisters” and other lifted areas can appear after you take a veneered panel out of its clamps. Check for lifted areas by lightly running your fingertips across the veneer while listening for any change in pitch. To repair a blister, slice into it at its edge, holding the knife at a steep angle away from the blister. Then inject glue into the cut under the loose area and reclamp the panel.
About Our Author
Jonathan Benson has shown his handcrafted furniture nationwide for over 30 years. Currently he teaches workshops around the country. He’s written magazine articles and books, including Woodworker’s Guide to Veneering and Inlay and Woodworker’s Guide to Bending Wood. To learn more about Jonathan, visit bensonfurniture.com.
Laying up a 4-way match
This simple exercise walks you through the basics of matching, sawing, and assembling veneers to create a “four-way” match panel, like the one shown at left. Here, I’m using four pieces of walnut burl veneer taken in sequential order from a flitch.
1 With the sheets stacked in their original sequence, number them from top to bottom, and then wrap blue painter’s tape around the edges in several places to keep the stack intact during layout and cutting. Lay out a match using two 1⁄8"-thick mirrors set square to each other. Tape their rear edges together and use a grooved panel to capture the top edges (Photo H). (My panel is grooved at various angles to lay out 4-, 8-, 12-, and 16-way matches.) Shift the mirrors around on the veneer to preview a variety of layout options. Once you find the match you like, mark out the rough outlines by tracing along the mirrors.
2 Guiding a veneer saw along a wooden straightedge, saw through the stack of veneers, cutting about 1⁄16" shy of your layout line (Photo I).
Hold the straightedge down firmly while pressing the bottom of the saw against its edge. Make a series of light passes until each offcut separates from the sheet. Once you’ve cut through all the sheets, tape the sawn edge for stability, and then cut just shy of your second layout line in the same manner.
3 Joint, or shoot, one of the edges of the sawn stack straight to create gap-free seams. I use a straight-edged clamping jig, as shown in Photo J, but you can simply place the stack of veneers between two boards clamped in a vise. Align the upper edges of the boards with one of the two cutlines you drew during the mirror layout process and plane or sand away the projecting veneer edges flush with the edges of the boards. For tear-out-prone woods, I prefer to use sanding sticks instead of a hand plane. I begin with 80 grit; then follow up with 120 grit.
4 Untape the package and renumber the sheets in sequence if the original numbers were lost to the saw. Then lay out sheets 1 and 2 in paired form, flipping one sheet over to create a mirrored “book-match” with the jointed edges abutting. Do the same with sheets 3 and 4. With the “show” faces down, use a few short pieces of blue painter’s tape to hold the seams together (Photo K).
5 Flip each taped pair over and check the seam alignment and the grain match, making alignment adjustments or reshooting if necessary. When the match is balanced and the seam tight, apply wet veneer tape to the show faces, as shown in Photo L. Briefly apply high heat from an iron to the tape to dry it. Then remove the blue tape from the back.
6 Now prepare the seam for joining the two pairs. First, tape them together at the edges, with the show face on the inside of the package and the previously joined seams precisely aligned, one on top of the other. Register one edge of a drafting triangle against the previously joined seam, and extend a cutline along the adjacent edge (Photo M). Then repeat the procedure across the other half.
7 Again using a straightedge as a guide, saw to your cutline. With the pieces still taped together, shoot the edge as before. Remove the tape and place the two assemblies together, show faces down with all four seams intersecting at the center. Use pieces of blue tape to connect the seams, and then flip the panel over to inspect the front for a symmetrical match. If either seam needs additional work, reshoot both edges, removing the same amount of material to maintain the pattern symmetry. When everything looks good, tape the seams on the show side with wet veneer tape as before (Photo N) and remove any remaining blue tape from the back. The “laid-up” sheet of veneer is now ready to be glued to a substrate.
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