The copper notebook
Useful knowledge,
kept concise.
Practical notes on choosing and using copper wire, with clear answers to common questions at the bonsai bench.
01Why annealed copper?
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What changes when copper is annealed, and why artists use it for structural work.
Soft to apply, firm once worked
Annealing softens copper before it is applied. As it is wrapped and bent, the wire work-hardens, helping it hold the position of a branch with a relatively slim profile.
A place on conifers
Copper is often chosen for pines, junipers, and other conifers when a structural bend needs a secure hold without a bulky wrap.
02Copper vs. aluminum bonsai wire
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Both have a place at the bench. The tree and the job should decide.
Where copper excels
Copper is often preferred for conifers and fine structural wiring. It can provide a strong hold with a thinner wire than aluminum, and its surface darkens as it oxidizes, making a careful wrap less conspicuous.
Where aluminum makes sense
Aluminum is usually preferred for deciduous and tropical material. It is easier to handle while learning and more forgiving when a wrap needs adjustment. Copper is usable on these trees, but branch sensitivity and growth call for extra care.
Reuse and feel
Once copper has been bent and removed, it no longer has the same soft feel as a fresh annealed coil. Do not count on used copper for another clean wrap.
03Choosing wire size
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A starting gauge is useful. The branch still gets the final say.
Start with the branch
A wire near one-third of the branch diameter is a common first guess for moderate movement. Test the hold instead of treating that ratio as a rule.
Adjust for the actual bend
Wood stiffness, branch length, anchoring, and the amount of movement can all change the gauge you need. A short, stiff branch may call for more support than a long, flexible one of the same thickness.
04Wiring angles
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Consistent spacing and contact matter more than a single magic number.
Keep the spiral consistent
Apply each turn at a deliberate angle with even spacing and steady contact. Avoid stacked turns, crossings, and gaps that leave the bend unsupported.
Use the angle that serves the bend
A 45-degree spiral is commonly taught, while some practitioners favor a more open angle. The branch, wire, and movement determine what works; do not force every wrap to an exact number.
05Anchoring wire
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A stable starting point lets the wire hold the bend instead of spinning.
Anchor before bending
Secure the start of the wire to a suitable branch, trunk section, or other stable point. If the anchor turns when you bend, the wire cannot do its job well.
When a guy wire helps
A protected guy-wire attachment can apply a controlled directional pull when a spiral alone is not the best tool. Protect contact points and check them as the tree grows.
06Single vs. double wiring
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Two related techniques with different anchoring choices.
Single wiring
One length of wire supports one branch, with a secure anchor before the first bend. It is often the cleanest choice when the wire gives enough hold.
Double wiring
One continuous length can wire two nearby branches of similar thickness, with the run between them acting as the anchor. Adding a second parallel wire to one branch is a separate way to increase support when needed.
07When wire should be removed
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Watch the tree rather than relying on a fixed calendar date.
Check for pressure
Inspect wired branches regularly and remove or adjust wire before it cuts into expanding bark. The timing varies by species, season, and growth rate.
Work section by section
Fine tip wire may need attention before heavier structural wire. Check each area on its own rather than removing everything by one schedule.
08Safely removing copper wire
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Protect bark, buds, and the set you worked to make.
Cut in short sections
For most wired branches, snip the coil with bonsai wire cutters and lift away short pieces instead of pulling a hardened spiral back around the branch.
Support delicate growth
Take extra care around buds, junctions, and fine foliage. Use the removal method that causes the least movement or damage to that particular branch.
09Why copper work-hardens
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The material changes as you shape it.
Bending makes copper stiffer
Annealing softens copper. Bending and wrapping then change its internal structure and increase its resistance to further bending. That is why a fresh coil feels different from wire already worked on a tree.
Handle it with intent
Avoid repeatedly straightening and re-bending a section before applying it. Work from a fresh coil and make each wrap deliberately.
10Wire storage
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Keep the right gauge easy to find and easy to use.
Keep gauges labeled
Black Magic coils are labeled by gauge and length. Keep those labels with the wire or transfer them to your own rack so you can identify a size quickly.
Prevent kinks and tangles
Store coils neatly in a dry place and let wire pay out without sharp bends. A simple rack, drawer, or divided box is enough.
Bench tool 02
AWG to metric,
without the guesswork.
Established AWG dimensions for a fast measurement check while you’re working.
Diameter sourceASTM B258NBS Copper Wire Tables (free PDF)These are nominal AWG diameters, not measurements of individual coils. Metric values are rounded to 0.001 mm.