วันศุกร์ที่ 2 เมษายน พ.ศ. 2553

Getting Started With Wood Veneers

To many woodworkers, the subject of veneering brings one of three emotions. One is the thought that it is an inferior form of woodworking. This is a misconception. The second would be that it's too complicated to learn, and therefore beyond their current capabilities. This also is not true. The third is that furniture made from veneers is of poor quality. This couldn't be further from the truth.

Some of the finest furniture in the world would not have been possible without the use of veneers. The opportunities to create many patterns and matches just wouldn't be possible using solid lumber. If someone tried, the result would self destruct.

Veneering has been around for at least fifteen hundred years, as proven by some pieces removed from the tombs of the Pharaohs of Egypt. These pieces were removed, still intact, and in good condition. Veneers are thinly sliced, typically 1/40 of an inch thick or less. This provides many pieces of veneer with almost exactly the same grain pattern, as the piece before it. They are kept in the same order as they were on the tree. This makes matching patterns possible.

One of the advantages to using veneer is the finest lumber is sent to the veneer mills. This way the very best of woods can go considerably further. Imagine how many pieces you could cut from a log, when slicing it 1 inch thick, as opposed to 1/40 of an inch thick. Patterns that can be produced are radial, which could include as many as forty individual pieces, although cutting that would be extremely difficult. Book matching which is opening two pieces of veneers the same as you would open the pages of a book.

This will create a grain pattern which meets in the middle and offers considerable beauty.

Slip matching is taking veneers in order, and sliding the sheets over, one next to the other, but keeping the same side up. The will result in a repeating pattern. With certain woods, this can be a better approach, as when the pieces are flipped over they have a different light reflection property and can look like the colors aren't matched properly. The tools used for veneering are relatively few. A knife or scalpel can be used to cut them, or a saw made specifically for cutting veneer. A roller, much like a wallpaper roller in used to flatten the veneer into the glue, and more often to apply pressure to the veneer tape.

A veneer hammer, which is more like a squeegee, than a hammer, is used to squeeze the excess glue from under the veneer, and ensure a good contact across the entire project.
This hammer is generally used when working with hot hide glue.

A self healing cutting mat like those found in a sewing store, which serves as perfect cutting surface. Some blue painters tape to hold the veneers tight together while you fabricate the patterns. Veneer tape, which is gummed on one side, which when wetted will stick the veneers together for the final lay up. This tape is often perforated, and is referred to as either two hole or three hole tape. These holes allow you to see that your seam is tight between the pieces being connected. A tape dispenser, while not necessary is pretty handy. This will wet the tape as its being pulled out of the dispenser. The roller, mentioned earlier is used to apply pressure to the tape. As the tape dries, it shrinks, pulling the joint even tighter. A straight edge is also needed to cut perfectly butting joints, with no visible gaps between the pieces being joined.

Veneering offers the possibility to combine several species of wood for contrasting borders and inlays. It also leads to the possibility to continue on to marquetry, which is much like cutting a puzzle out of contrasting woods to form a picture. Modern veneering techniques often include the use of a vacuum system to press the veneer into the adhesive in a uniform fashion. Prior to vacuum systems, veneer presses were built to apply as even pressure as possible on the veneer, while being glued. The adhesives used today are also more convenient the hot hide glues. Hide glue is actually ground up hooves, bones and other animal parts. It doesn't smell too pleasant either, as it's heated for use. Working temperature is about 140 degrees for this glue.

Generally a two part adhesive is a better choice, as it provides a rigid bond. Glues like yellow glues are too flexible and allow "creep", or movement in the finished product.

The exception to this is when both surfaces are coated with yellow glue, also known as P.V.A. glue, and permitted to dry completely. The two pieces can then be ironed on with a common household iron. This creates a very strong bond, as it cross links the properties of the glue. After about twenty four hours, it cannot be reversed. The use of contact adhesives is not recommended for veneering. It allows too much movement, as it remains flexible forever. Also, common household items can weaken the bond, even through a finish. Veneering can be a very relaxing form of woodworking, as well as quite rewarding due to the unlimited combinations that are possible. Combinations that simply wouldn't be possible using solid woods. While the idea of learning to work with veneers may be intimidating, it's a matter of trying it, and learning as you go.

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