WHAT IS STEAM BENDING?
Steam Bending is a term used to describe heating wood to boiling point to soften it, so you can bend/twist/squash it into new shapes.
The plant-cell-walls in wood are a composite of about 50% Cellulose Fibers (what paper is made from) and 30% Lignin (a natural thermo-plastic). If you heat Lignin to boiling point (100 degrees Centigrade) it softens enough to allow the cellose fibers to move in the wood to enable the whole piece to yield to a new form.
When the wood cools the lignin bonds set again and when the wood dries (below 12% moiture content) the bend becomes permanent.
Steam Bending is a process that opens a lot of doors creatively. Knowledge of the process not only allows makers, wood workers and artists to gain a deeper, more accurate insight into the real nature of wood, but also provides the practical tools to fabricate designs that wouldn't otherwise be achievable by any other process.
EXAMPLES OF DIFFERENT BENDS
Steam Bending is a cheap, clean, efficent and eco-friendly process that lets you bend solid wood - no glue, cleaning up, or gluelines and it can be done by anyone.
Steam Bending is great with air-dried or fresh ‘green’ wood. The steaming and drying process will leave you with wood at around 8% moisure - a shortcut to seasoning and makes using a locally sourced wood a viable, economical and desirable option. You can also use kiln dried wood too, however for extreme bends green wood is easier.
With the right wood and a well designed ‘jig‘ or form, Steam Bending will give you simple reliable results every time. The process lends itself to batch production as well as sculptural exploration!
Almost everything you need can be bought at a builders yard or DIY store. We also have a selection of equipment available to buy in our kit store.
You will need:
Any way of boiling water and venting/piping the steam into a steam chamber. A $20 electric 'wall paper stripper' is very convenient but you will also find many other good solutions, gas is used by most professional makers as you can adjust the output for maximum efficiency. You can also boil or microwave the wood if possible/practical with great success, and fire can be used too for certain bends.
Really anything to contain the steam which you can get the wood into. Plastic pipes are great (be aware PVC gets soft when hot, HDPE or Polypropylene are better), plywood boxes are good, we make boxes of 50mm foam lined with thick polyethene as they are lightweight and very well insulated. Lids, racking, faceplates, venting pipes etc… can all be added if desired. You need to make sure the wood really is 100 degrees Centigrade for best results. Digital ’meat thermometers‘ are great for checking the temperature inside.
The most important skill in steam-bending is knowing how to look at wood and understand what you are looking at. If you are a beginner buy straight grained Ash or Oak that has not been kiln dried, or for free experiment with fresh branches. Generally 'ring-porous temperate hardwoods' are best, however there are a lot of exceptions. Top five woods for steam bending in our workshop are: Oak, Ash, Elm, Yew and Walnut. All wood is made from Lignin and Cellulose, and so all wood can be steam-bent to some extent, we also love experimenting with Plywood, Softwoods and Reclaimed wood which is much trickier but can give fantastic results.
A ‘jig’ is a generic term for a tool made for a particular purpose, and for steam-bending these are almost always home-made. If you are starting out, for a 'bending form' (a jig to bend around) find something solid with a radius simelar to what you want (a spare wheel, stone pillar, lamppost!) or cut the shape (-15% of the final desired radius) from plywood.
These are normally ‘G-Clamps’. If you are starting out I recommend buying at least one decent square threaded G-clamp such as by Bessy and other cheaper ones for holding wood in place. As you make ‘jigs’ you may start to use wedges to clamp the wood which is very fast, effective and cheap.
Only needed for tighter bends or thicker wood. This is normally a peice of >1mm thick steel secured to the ends of the hot wood, on the outside of the bend. As wood will break (snap) in tension before (kinking) in compression, a compression strap which does not allow the wood fibres to stretch at all enables bends to be much tighter.
Types of strap include ‘wedged‘, ‘adjustable’, ‘hydralic‘, ‘friction‘ and ‘sliding‘ (all terms refor to how the wood is secured and managed during the bend) and materials include galvanised or stainless steel, woven stainless steel and composite for the strap itself (don't use ratchet straps as they will stretch). If you are starting out and want to try thicker bends I recommend making a classic ‘wedged compression strap’ and taking from there, or buying the Veritas Adjustable Compression Strap for thick narrow boards.
WOOD & STEAM BOOK
A good starting place with the process is our book 'Wood & Steam' published by Kyle Books which covers the most basic aspects and provides starting points for 18 simple projects