Styling with wire.

Stymie — Wed, 30 Jan 2008 00:24:21 GMT

When wire is used to reposition twigs, branches or trunks of trees with a view to improve the design, some things are best kept in mind. The thickness used should err on the larger side rather than the smaller or the holding power will be insufficient for the purpose. Progressively thinner sizes will be used as we get further away from the trunk. To test if your wire is strong enough, hold a peice about 2½ inches from the end. Press the twig or branch with it and if it moves its strong enough.

When wire is in position during a period when active growth is taking place in the subject, it will not need to be in position for as long and it should be inspected frequently to ensure that it does not start to bite into the bark. This could cause unsightly grooves or scars. A secure anchorage must be the start of any wiring e.g. a couple of turns around a part of the tree, which is stronger than the part to be modified. Then the wire should contact first on the outside of intended bends before winding along the branch/twig at an angle approximating 45 degrees and taking care not to trap small twigs or leaves under it.

Any bends made then seem to hold better if a slight twist in the same direction as the wire route is made at the same time as the bend. Woody growth is more likely to snap when being bent and may be taken to its new position in stages with rests in between . A procedure to stop bark from being lifted as the bend is made is being used more frequently these days. This is to bind the area with soaking-wet raffia, which shrinks slightly as it dries or with some kind of tape before applying the wire. The bark is stretched on the outside of bends and compressed on the inside. The binding holds it in contact with the wood and keeps the feeding streams intact. This is not necessary when dealing with thinner, less woody areas.

Mature trees in general, have branches, which become more horizontal as they age. Their attitude is due in part to environmental influences such as wind and snow, which may bend them this or that way. What we are doing with the wire is acting like these other influences on juvenile growth to make it look older or as though it has been battered by the elements for years. Guy wires, which are sometimes anchored to the pot or a dead branch to pull part of the tree toward them, are sometimes left on for long periods. To avoid damage, the live parts in contact with the wires must be protected with something like foam or plastic sleeving which spreads the applied force over a wider area.

Behaviour of copper and aluminium wires

You may have noticed that copper, size for size, has greater holding power than aluminium when used to shape branches and twigs. This is because it hardens more when it is worked or bent. In fact the strength of copper after bending can be almost three times greater than when you start using it. To try to explain why this is we have to look at the molecular structure. It has a cubic crystal which allows for easy bending, however, as it is bent, the crystals are deformed and cling to each other more rigidly making further bending or working harder. In other words, it holds better for bonsai purposes.

Aluminium wire does have the same qualities but nowhere near as marked as the copper. A benefit of this characteristic is that it can be reversed by the process of annealing, which brings the crystals back into their original uniform cube shape, so allowing the easy bending property to be regained. To anneal your wire for re-use, bring it up to a dull red glow and allow to cool. Bear in mind that it will scorch anything with which it comes into contact while hot, including skin, so hold it firmly in your pliers or some such incombustible tool while you heat it. I use the gas ring for annealing, which does not deposit soot on the wire like some other methods of heating.

A further point is that, particularly with the larger diameters, the mere action of uncoiling copper wire, hardens it appreciably, so if you are going to re-use a comparatively short length, keep it straight until needed.

The presence of copper in the compost slows down root extension, so if you use copper wire to hold the drainage mesh in place, your drainage holes do not get clogged up by the roots as easily.

A small contra-indication to the use of copper as opposed to aluminium is that you do not need to use such a large diameter and it is more likely to cut into the bark if left on for too long.

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Styling with wire.