Art Nouveau is a decorative style easily recognised by its sinuous, curvilinear forms often based on the exaggeration of vines, flowers and foliage.
Beginning in the late 19th century, Art Nouveau reached its peak in 1900 with the Exposition Universelle in Paris before all but petering out by 1914. 
A description of Art Nouveau published in Pan magazine of Hermann Obrist's wall hanging Cyclamen (1894) described it as "sudden violent curves generated by the crack of a whip", which (description) became well known during the early spread of Art Nouveau. 
Subsequently, not only did the work itself become better known as The Whiplash but the term "whiplash" is frequently applied to the characteristic curves employed by Art Nouveau artists. 
Such decorative "whiplash" motifs, formed by dynamic, undulating, and flowing lines in a syncopated rhythm, are found throughout the architecture, painting, sculpture, and other forms of Art Nouveau design.
Art Nouveau architecture made use of many technological innovations of the late 19th century, especially the use of exposed iron and large, irregularly shaped pieces of glass for architecture.
By the start of World War I, however, the stylised nature of Art Nouveau design—which was expensive to produce—began to be disused in favour of more streamlined, rectilinear modernism, which was cheaper and thought to be more faithful to the plainer industrial aesthetic that became Art Deco.[en.wikipedia.org/wiki/Art_Nouveau]
Above: Art Nouveau is rarely so fully in control of architecture: doorway at place Etienne Pernet, 24 (Paris 15e), 1905 Alfred Wagon, architect.
Above Right: Art Nouveau House in Aveiro, Portugal
Art Nouveau Architects
His 1872 book Entretiens sur l'architecture influenced a generation of architects, including
Above Left: Architecture of French Hector Guimard
These three famous Art Nouveau architects made quite an impact in the short span of time when the Art Nouveau style was all the rage.
Victor Horta, Paul Hankar and Hector Guimard set out to tranform the most plain and functional buildings, houses, hotels, public works buildings and even subway entrances, into works of art. They took inspiration from the beauty inherent in nature as they designed buildings that allowed for flowing, curvaceous lines and organic shapes. These three architects left behind a legacy of beauty and grace.
Above Left: Horta's house-studio. Detail of the facade Above Right: Guimard's famous entrances to the Paris Métro, based on the ornamented structures of Viollet-le-Duc.
Art Nouveau in Australia
Although no significant artists in Australia are linked to the Art Nouveau movement, many buildings throughout Australia were designed in the Art Nouveau style.
In Australia, Art Nouveau was spread by the growth of art and craft education in technical schools and adopted by various commercial enterprises but it was rarely used for complete room or building schemes.
Left: 3 Ballarat Street, Yarraville
Melbourne architects Sydney Smith and Ogg designed this handsome example of Art Nouveau-inspired architecture for a flourishing post-federation Yarraville in 1909.
The contract price paid by State Savings Bank Victoria was £1,966.
Perhaps most significant to its design is the fact that renowned architect, architectural author and academic Robert Haddon was employed by the firm at the time.
In Melbourne, (above) the Victorian Arts Society; William Massey built the Victorian Artists Society at 430 Albert Street in 1892 to the design of architect Richard Speight Jnr. (Son of the Railways Commissioner)
Milton House (left) built in 1901 and designed in the Art Nouveau style by architects Sydney Smith & Ogg,
Art Nouveau Elements
You can identify Art Nouveau style art and architecture by looking for some specific elements.
Art Nouveau is characterized by graceful, sinuous lines. The lines are rarely angular.
Some artists referred to the curves in Art Nouveau works as whiplash curves. Rhythmic patterns of curvy lines are characteristic of this art style. These curvy lines connect the images in the art and can even be found in beautified plain items, such as dishes, eating utensils, hardware and furniture.
Organic Subject Matter:
You'll find plenty of flowers, leaves, vines, grass, seaweed, insects and other organic images in Art Nouveau jewelry, hardware, windows and architecture. Examples include images of birds etched into window frames or curled around each other on fabric for upholstery, or abstract lilies drifting around and connecting to each other on dinnerware.
Instead of classic gemstones, Art Nouveau jewelers opted to work with opals and semiprecious stones. Glass art reached a new level of popularity as Louis Comfort Tiffany and Charles Rennie Mackintosh took interest in the new art style. Molded glass, animal horns and ivory tusks became commonly used materials.
Resistance of Classical Restrictions:
Instead of limiting art to painting on a canvas or sculpting out of marble, Art Nouveau artists and architects looked for ways to make everyday objects into pieces of art.
A doorknocker might be molded to look like a dragonfly;
an entranceway might be graced by vine-like lines in the molding.
You can find a classic example of this by studying the entrances designed for the Paris Metro by Hector Guimard.
Above: Gustave Serrurier-Bovy - Belgian (1858-1910) Cabinet-vitrine,
1899 narra and ash with copper and enamel mounts The Metropolitan Museum of Art, New York, Gift of Mr. and Mrs. Lloyd Macklowe
Below: Charles Rennie Mackintosh - Scottish (1868-1928) Ladies' Luncheon Room from Miss Cranston's Ingram Street Tearooms, 1900 Glasgow Museums, Art Gallery and Museum, Kelvingrove
Above Right: Tiffany Studios American (firm active 1902-1932) Dragonfly table lamp, c. 1910 stained glass and bronze Chrysler Museum of Art, Norfolk, Gift of Walter P. Chrysler
Native flora and fauna
Left: Robert PRENZEL, Fireplace surround
The idea of using native materials pre-dates the introduction of Art Nouveau as does the idea of using native flora and fauna. In fact natural motifs were widely used in the stucco and brick relief sculpture in Romanesque revival buildings in the 1880s and 1890s, particularly in Melbourne.
Left: The Robert Prenzel wardrobe
Below Left: Robert Prenzel, The Davies Suite,three-piece suite of bedroom furniture (c1910).Collection: Art Gallery of Ballarat, Victoria.
"Prenzel took the prevailing art nouveau style, with its elegant simplicity and sinuous lines, and incorporated it into symbols reflecting the dawning nationalism of that Federation era, with its cult of the wattle and other Australian motifs.
"This furniture encapsulated that sense of pride in the nation and you celebrated your pride by covering things with native flora and fauna. For a 10-year period between 1905 and World War I, Prenzel was extraordinarily popular and basically every grand house in western Victoria had a staircase or furniture by him." *
In 1888 Robert Prenzel visited Melbourne from Prussia to view the Centennial International Exhibition and remained there to establish himself as a cabinet maker and wood carver.
Prenzel commenced his work in Australia with carvings in his highly elaborate and individual version of the German Renaissance and Rococo Revival styles - working on such major projects as the carving of the ceiling and walls of the west wing of St Patrick's Cathedral, Melbourne.
Prenzel also travelled to the Western District of Victoria on several occasions, and would carve elaborate staircases from Blackwood.
One such staircase is at 'Purrumbete' a well known historic home near Camperdown.
In 1906 Mrs Mathias of Montreal visited her sister and brother-in-law, Mr and Mrs Stuart Black, at their property 'Glenormiston' at Terang.
The Mathias suite is lavishly decorated with floral and faunal Australian motifs. It is thought that Mrs Mathias may have requested such decoration as a memento of her visit to Australia, but when adding to the suite in 1908, it would seem that the choice of motifs came from Prenzel himself.
His carving of Australian flora was exact in many instances, and sufficiently accurate botanically for the species depicted to be easily identified. Prenzel did at times however, adapt his designs in the interest of artistic balance.
Prenzel became very interested in the subjects of his Australian carvings and at his home in Black Rock in 1903 his garden had a comprehensive collection of native plants which he would use to assist him in his work.
Left: A Harvey school gum-nut art nouveau ashtray, Australian circa 1930
The Harvey school:
L. J Harvey was an important practitioner and teacher in the arts and crafts movement in Queensland and a figure of national significance. Harvey was an accomplished artist, carver, ceramist and sculptor, as well as the inspiration of the largest school of Art Pottery in Australia.
In 1938 Harvey opened an applied art school in Adelaide Street, Brisbane and taught a wide range of people and was associated with the most significant Queensland artists of his day. Daisy Nosworthy and Florence Bland are just two students 
Below Left: The Gumnut Ball
Below: Art School in 'Little Ragged Blossum'
Centre Right: The book 'More than a Fairy Tale. An Artistic Life' by Robert Holden and Jane Brummitt
Below Right: Gumnuts - a rear view
Cecilia May Gibbs MBE (17 January 1877 – 27 November 1969) known as May Gibbs was an Australian children's author, illustrator, and cartoonist.
She is best known for her gumnut babies (also known as "bush babies" or "bush fairies"), and the book Snugglepot and Cuddlepie.
In 1916 she published Gumnut Babies, the first of the Gumnut books she had written and illustrated.
She also wrote other books, sold book-marks, small calendars and other novelties with gumnut and blossom babies.
Her readers reacted to her 'sense of fun' and surprised her publishers, Angus and Robertson Ltd, by scooping up 17,000 copies of Snugglepot and Cuddlepie (1918) on its first release.
Gum nuts, kangaroos, emu, kookaburra and such, were part of Arts and Crafts decorative design and blossomed profusely during Art Nouveau.
But the influence on Australia of William Morris' movement and his followers, such as architect C. R. Ashbee's arguments for a cottage design or style was limited more to spiritual resolve than material substance, and to a limited audience.
Art Nouveau emphasized handcrafting as opposed to machine manufacturing, the use of new materials.
Principal subjects are lavish birds and flowers, insects and polyformic femme fatale. Abstract lines and shapes are used widely as a filling for recognizable subject matter. Art Nouveau artifacts are beautiful objects of art, but not necessarily very functional.
- Sydney Architecture Images- Art Nouveau
For architecture the potent ideas in England of those supporting the medieval cottage led to more flexible ideas of the bungalow which evolved in England and then matured in America at the turn of the century.
Art Nouveau offered no direct lineage to the future as did the theoretically stronger Arts and Crafts movement.
Art Nouveau tended to be superficial in its application to architecture.
Buildings containing elements of Art Nouveau were usually part of the cottage ideas or the relatively new ...Queen Anne revival, an architecture of many angular roof forms and white posted verandahs.
- Australian Architecture 1901-51: Sources of Modernism
Melbourne Art Nouveau
Sydney Art Nouveau
Above: Home with Art Nouveau elements, 75 London Street, Enmore, NSW
Interiors: 3 Park Rd, St Leonards NSW
Above: Two views of 113 Brook Street Coogee (may be demolished)
See also post Art Nouveau in Malvern East
From: Leadlights of Artarmon
Features of an Art Nouveau style leadlight:
Long, flowing curved lines
Plant motifs – flowers, leaves, stems
Large proportion is coloured glass
Australian flora and fauna
Below: Standing on a very large block, well back from the road, this wonderful Edwardian villa featuring a concoction of Art Nouveau fretwork and stained glass, half timbered gabling and tall chimneys, may be found in the Ballarat suburb of Wendouree.
Above Left:The Art Nouveau Stained Glass Lunette of Queen Anne Style Villa - Ballarat By raaen99
Above Right: The Art Nouveau Stained Glass Window of Queen Anne Style Villa - Ballarat By raaen99
Australian Art Nouveau Housing
Art Nouveau was applied to a variety of tried and successful architectural styles including the Arts and Crafts cottage.
The mix of Arts and Crafts with Art Nouveau, cannot be too heavily stressed.
The pure new art of Belgium and Europe arrived in Australia about 1900 or so, but it was an English derivation organized about cottage and Romanesque ideas and forms.
More often than not it was a heavily massed architecture with surfaces of glass or white wood which received a touch of Art Nouveau form, line or colour.
Historian John Freeland's statement that in the hands of Australian followers and imitators ‘Art Nouveau was sterilized into utter superficiality’
This was true of most of Art Nouveau architecture. The very tenuous whipped lines extending into the architecture of Frenchman Hector Guimard's buildings have few equals in the rest of Europe and none in Australia.
Australian Art Nouveau interiors
See also archived Architect Harold Desbrowe-Annear
See also archived Chadwick House Eaglemont
See also archived Architecture of Harold Desbrowe-Annear
- 21 JUNE 2019
Architect Harold Desbrowe-Annear was the pioneer of the medieval movement in Australian home design, especially in Melbourne's north-east.
Born into a Bendigo mining family in the 1860s, raised on Westbank Terrace, Richmond and matriculating from Hawthorn Grammar, Anneal was articled in the office of the architect William Salway.
Salway's office was designing trophy homes,
Raheen for Edward Latham in Kew, Moondah for James Grice at Mount Eliza and
Millswyn Court for James Gatehouse in South Yarra.
Desbrowe-Annear was especially following the English Arts and Crafts movement closely.
He became responsible for much of the medieval inspired work in Heidelberg, Ivanhoe,
Greensborough and Alphington.
His Macgeorge house at the confluence of the Yarra River and Darebin Creeks is still viewed as a stunner.
In the early 1900s the then Ascot Vale-based Desbrowe-Annear and his wife Florence headed to live at Eaglemont near Heidelberg.
His father-in-law James Chadwick had paid £170 for three building blocks high on Mount Eagle.
The couple built a home for themselves.
Their home differed to the other two as it initially had a corrugated iron roof, painted red to replicate the expensive Marseilles-pattern metal tiles. The tiles were added at a later date.
Read more: at PropertyObserver.com.au
Three houses by Harold Desbrowe Annear in 1902–3 for a steep site on The Eyrie, Eaglemont, Victoria, were the fullest, most complete Art Nouveau in Australia. They were not the pure English or European variety.
They owed a great deal to the traditional nineteenth century, something to Queen Anne, and to Queensland verandah domestic style of a bulk raised on posts (‘stumps’) with wood dominating structure, surface and ornamentation.
Annear's designs had subtle changes in level within, sliding doors to change spatial appearance and size, as well as rather nontraditional plan forms, all suggesting ideas of the open plan.
The exterior forms were unpretentious and related to the bungalow by their informalarrangement and materials. Ornamental characteristics of rhythmical verticals in a suggested half-timbering were contrasted by sweeping curves which recalled Art Nouveau and the Queensland precedents.
Their overall effect, therefore, was related to Art Nouveau: fluidity of space and form, strong sweeping lines and the whole conceived as a related unit without traditional or formal encumbrances such as ornament or axiality
But the Annear houses (one was his own) were exceptions. In general, Art Nouveau suffered from the general misconceptions of eclecticism and resulted in another pastiche.
Chadwick House sits in 1,460 square metres of established gardens on The Eyrie with views capture by the Heidelberg School artists including Arthur Street and Walter Withers who had mixed socially with the Desbrowe-Annears.
The home was first sold in 1922. It last traded in 1988 at $715,000 when sold by university professor Robert Reid to the architect Peter Crone and wife Jane, who undertook an award-winning restoration.
The home has been returned to its original condition, winning the national award for heritage from the Australian Institute of Architects in 2008 for Crone, who first became aware of Desbrowe-Annear in the 1960s.
Chadwick House, has been recently listed for sale at $3 million.
It is an Arts and Crafts style home with half-timbered roughcast walls, a hipped and gabled Marseilles-patterned tile roof, arcaded chimney stacks and cantilevered gables.
Below: Architect Peter Crone's meticulously restored home, Chadwick House in Eaglemont, designed by Harold Desbrowe-Annear in 1903. Photo: Neil Newitt
Architect Robert Joseph Haddon
Robert Joseph Haddon, an English trained architect, was one of the few to work in the Art Nouveau style in Australia.
Above: Detail of Art Nouveau ornament on Milton House, 21-25 Flinders Lane Melbourne
Below: 'Australian Architecture' by Robert Haddon (1908)
Click the image to read the book online at Deakin University Online Library
Australian Architecture 1901-51: Sources of Modernism, by Donald Leslie Johnson, University of Sydney Library, Sydney 2002
7. Australian Architecture 1901-51: Sources of Modernism
by Donald Leslie Johnson, University of Sydney Library, Sydney 2002
‘Anselm’, Haddon's own home in Caulfield Melbourne, contains wave like tiles in the Art Nouveau style in the bathroom and he applied the sinuous Art Nouveau lines to the outside brickwork.
Others used the stylised floral forms of Art Nouveau with the Australian Waratah, flannel flower, lyre birds, emus and kangaroo motifs.
Many buildings are supposedly attributed to Robert Joseph Haddon without actually bearing his name.
When Haddon practiced in Melbourne, much of his work was acting as a consultant to other firms, notably the practice Sydney Smith & Ogg.
The façades of Milton House, Flinders Lane (1901) and Eastbourne House, Wellington Parade (1901), are composed of carefully placed elements and ornament on plain surfaces, producing overall balanced designs.
Haddon was the author of Australian Architecture. A technical manual, published in Melbourne, by George Robertson, in 1908.
For generations this was the first true Australian architecture book. Before this we have some trade and technical literature, some government reports and scattered papers and, recently discovered, an extremely rare pattern book printed (but probably not published) in Melbourne in 1885.
Despite Haddon's approach (a textbook rather than pattern book), his examples can easily be traced to his own projects - domestic, commercial, churches, hospitals and shearing sheds. His city office in this book, for example, is a close relative to his Fourth Victoria building in Collins Street, Melbourne.
His work was modern, very much Arts & Crafts (or Federation if you like) at this period and he argues for a specific response to local conditions and materials and demands a modern, honest use of materials.