What is steaming timber?
Steaming is a timber treatment in which wood is exposed to steam to even out strong colour differences, prevent fungal staining during processing and make the wood easier to work. It is used mainly on hardwoods. Beech is by far the most commonly steamed species; oak and robinia are steamed as well.
The most visible effect is colour. Unsteamed beech is pale and can stain unevenly, while steamed beech takes on an even tone that ranges from light pink to a deeper reddish brown. Almost all European beech on the market is steamed before drying, which is why that pinkish colour is regarded as typical of beech. Research has also found that steamed beech changes colour less than unsteamed beech when exposed to light.
Steaming is also a pre-treatment. Hot, moist wood becomes temporarily more pliable, so timber is steamed before veneer is peeled or sliced from it, and before it is bent into shape, for example for bentwood chair seats and frames.
Recognising it
Steamed beech has a uniform pink to reddish-brown colour. Unsteamed beech is paler, from creamy white to light brown, and more often shows colour variation within a single board.
| Steamed beech | Uniform pink to reddish-brown colour |
|---|---|
| Unsteamed beech | Paler, from creamy white to light brown; more often shows colour variation within a single board |
In practice
- Buy from one batch. Steamed and unsteamed beech side by side, for instance on a staircase and a floor, will show an obvious colour difference.
- Do not treat it as exterior timber. Steaming changes colour and workability, but it does not make beech suitable for outdoor use.
- For steam bending, start with green or air-dried wood. It bends more readily than kiln-dried stock.
- Use a test piece. A widely quoted rule of thumb is about one hour of steaming per inch (25 mm) of thickness. Try an offcut of the same thickness and bend it straight out of the steam box.
- Let the piece cool and dry in the form, otherwise part of the bend will spring back.
Common mistake: confusing steaming with thermally modified timber. Thermally modified wood is treated at far higher temperatures to change its durability; ordinary steaming does not do that.
Related terms
- Veneer
- Hardwood
- Thermowood
- Wood modification
- Wood movement
- Wood species
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