The wood roof shingles on this onion dome were bent to match the curves of the dome. The church is in a compound known as the Kizhi Pogost.
Steam bending is a woodworking technique where strips of wood are steam heated using a steam box. The applied heat and moisture makes the wood pliable enough to easily bend around a mould to create a specific shape. The moulding process is usually done by clamping the strips of wood to a positive form, with the strips of wood often reinforced on the outside with a metal band to prevent blowout. The method has been used in the manufacturing of a diverse range of products, some examples being wooden boat building where it is used in the shaping of hull's ribs and lap boards, the production of traditional wooden lacrosse sticks, musical instruments such as violins and in the manufacture of wooden furniture like the Windsor chair and much of Michael Thonet's work.
Steam bending is a traditional process steeped in history. It was once a vital practice, paramount to the production of weapons, tools and water vessels, but with the advance of technology the practice has become less common. Steam bending is also a low energy, ecological and economical method of manipulating wood. It doesn't need the expense or drying time of glues to join together several wood pieces to make the desired shape. Steam bending also leaves lower levels of scrap since a smaller piece can be bent into shape instead of cutting the desired shape away from larger, more expensive stock.
Steam bending is limited in the degree of bend it can achieve, particularly for thick wood. Also, not all species of wood steam-bend well. It weakens the wood slightly and can leave residual stresses which may cause breakage, blowouts or spring-back over time.