Bentwood chairs are those distinctive chairs that have rounded pieces of wood, bent into curlicues, serving as arms, legs and stretchers.  They are exceptionally decorative and have been made consistently since their invention in the early 1800s.  The wood was soaked, steamed, molded and bent into various shapes.  Bentwood pieces were usually made from a variety of different woods.   Bentwood is most often used in cafe or bistro chairs and stools.  

THONET bentwood chairs are considered by most to be the most desirable of all the early bentwood chairs because the bentwood process was invented Michel Thonet (1796-1871).  Thonet was a German, (not French as many people think) living in Vienna, who created the bentwood process in 1836.  By 1870 his company, the Thonet Brothers, was the largest furniture maker in the world, making an astounding variety of furniture made of bentwood.   Thonet's patent expired in 1870, when several other companies went into production making bentwood, including Mundus and Kohn.  Most of the bentwood seen in the 19th century was made in France, Poland and Austria (Thonet had factories in all locations) and these pieces were shipped all over the world.   Thonet and its competitors Mundus and Kohn eventually merged into one company.  This company still exists to this day making bentwood products as well as plywood and tubular steel furnishings. 

Most early bentwood pieces were marked with the country of origin and/or the maker.  They were marked with stencils and/or paper labels -- usually marked in the inside of the rim under the chair's seat.  Look here carefully for remnants of the label or stencil if you are trying to determine if your bentwood chairs came from one of these major makers.  Remnants of paper labels still exist on many of the early chairs -- sometimes only the 'et' remains of the original Thonet label but a label remnant is sometimes enough to determine if this is an original Thonet chair or not.  The value of early bentwood is determine in many ways:  originality (i.e, no repairs or refinishing) and condition are important factors but the beauty and complexity of the design are also critical in determining value.  If it's a set, how many of the original set survived?  How complete are they? (sometimes they are missing pieces of bentwood).  Are they signed?  How complete is the signature?  If they are not marked by the maker, are they marked with the Country of Origin (Austria? Poland?).  All of these add to the value of a bentwood chair.  Precision dating of age is hard to determine since many early bentwood pieces were made consistently for decades (and are still made today).