Tuesday, June 27, 2017

Iron-On Veneer

Here's a simple technique for applying veneer to flat panels. I have used it with bandsawn veneer I made myself, with paper-backed commercial veneer, and this week I'm doing it with some camphor burl veneer purchased from an online supplier. 

These particular panels will be
door panels for a wall cabinet. I prefer using veneer in an application like this, where the corners and edges of the veneered panel are protected by a nice, beefy solid wood frame. If I have time I'll show you the finished project . . . but for today, I can show you this. 

I know vacuum bags are the preferred way to apply veneer these days, but this technique is especially well-suited to the Thousand-Dollar Shop, where we get by with minimal equipment. In this case, instead of a vacuum pump and bag setup, we use a clothes iron. And the results are spectacular. We take advantage of the fact that, for some time after it initially dries, PVA wood glue (including Titebond I and Titebond II) is thermoplastic.  Heat it up, and it briefly becomes liquid and sticky again. Sticky enough to develop a good bond!

If you've purchased veneer, leave it in its package until you're ready for gluing. Use either mdf or plywood as the core of your panel (if you want to sound knowledgeable, call it "the substrate"). Here I'm using 1/4" baltic birch plywood.

Begin by cutting the veneer and substrate to size. You don't want to have thin veneer overhanging the edges of your substrate, so make your veneer slightly larger than the finished panel, and then make your substrate slightly larger than that. You'll notice in the photos that there's a small margin, say 1/8", of bare plywood showing around the edges of the veneer.

If you go big into veneering, eventually you'll want to get a veneer saw, and learn several methods for cutting veneer, and for joining multiple pieces of veneer into a sheet the size you want . . . as it happens, this camphor burl veneer comes in larger pieces than I need for the door panels, so I'm simply using a utility knife and a steel ruler to cut the veneer on my self-healing cutting surface. I like the cutting surface because its bright yellow grid makes it almost an unconscious habit to keep my cuts parallel and square. You can do this on a clean sheet of plywood if you wish. Just don't do it on your nice smooth bench top!

Since I want the veneer slightly smaller than the substrate, notice how I offset the panel from the edge of the veneer, then place my ruler against the opposite edge of the panel. Holding the ruler firmly, I slide the panel away 

and gently run the knife along the ruler. By "gently," I mean that I don't press the knife down at all, but I let its weight do the work, for the first two or three strokes. Then I make a final stroke with gentle downward pressure, and I have a good, clean cut.

Once substrate and veneer are cut to size, use a foam roller to apply a uniform but not very thick coat of glue to both pieces. I put newspaper under the work while I roll on the glue, and do my best not to let things move around while I roll. This minimizes the amount of glue that gets on the face of the veneer and causes trouble later on.

Let the glue dry in open air until it is dry. You should see that there's a thin, uniform, plasticy film on the entire surface of the substrate and veneer. If there isn't, apply more glue to the areas where it's been completely absorbed.

A quick note on glue here: I have used Titebond for this process, with good results. Here I am using a product I got at Highland Woodworking called Heat Lock. The manufacturer claims this product is specially formulated for iron-on veneering. The manufacturer, veneersupplies dot com, also offers veneer softeners as well as materials and supplies for all methods of veneering. The instruction sheet for Heat Lock glue recommends using their softener on veneer that's straight-grained or birdseyed. Burl, they say, can be applied without softening.

Mask off the iron with a piece of kraft paper or cloth, to prevent scorching the wood and getting melted glue on the iron. Set the iron to "medium high" or just below "cotton." Don't put water in the iron, you don't want steam! Triple check the positions of the veneer and paper mask, 

and press down firmly with the iron. Move it slowly and smoothly back and forth over the whole panel a few times. 

Keep it moving fast enough to prevent scorching, but slowly enough to melt the glue and let the pieces really mate with each other. You need to do this a few times to get the feel for it, but it's a very forgiving process. If your piece is only partially stuck down, go over it again.

Then, you're done! The veneer should be stuck down flat - - - any bubbles or lifted corners can be addressed right away with more ironing.

When I got to this point, it was my bedtime, so I clamped the panels together face to face (clean paper in between) to hold them flat until I can veneer the opposite faces. Veneering a panel is like doing algebra: anything you do to one side of the equation must also be done to the other side. If you don't follow this rule, you'll see warping.

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