BuYun Chen begins Empire of Style: Silk and Fashion in Tang China as any smart historian would, with the 2014 media storm over the plunging necklines in a TV show about Empress Wu. History’s best-loved bad-girl, Wu the Treacherous Fox even managed to scandalise from beyond the grave, causing modern-day Chinese censors to clutch their pearls in horror at the sight of all that medieval cleavage. More than a thousand years after the fall of the Tang dynasty, its fashions were still too hot for TV.

In an age when sumptuary laws tried to dictate an unofficial uniform for every class and profession, “the experience of dress and adornment [was] fundamentally one of meaning-making for the wearer, viewer and chronicler.” Chen details the weaves and patterns of a boggling array of beautiful medieval clothes, both extant and merely described, as well as the baubles and diadems that adorned many a princess’s head-dress and tiara. Nor does Chen limit her account to human fashions, detailing the elaborate decorations of the dancing horses of the Xuanzong Emperor, “with saddles of gold and silver, their manes and forelocks adorned with pearls and jades.”

Her materials are wonderfully diverse, spanning museum collections from Tokyo to Turfan, encompassing not only paintings, the poems of Li Bai, chroniclers’ descriptions and sculpture, but also tomb figurines from the western Chinese desert and pawn-shop receipts in the name of 7th-century dyers and “hairpin artisans”. Just as silk was regarded as a more durable and exchangeable currency on the frontier, textiles – necessary but discretionary – were one of the most common articles pawned in times of crisis.

Chen describes Chang’an (modern Xi’an) in all its medieval cosmopolitan glory, at the height of the reign of the Xuanzong Emperor, when the Serpentine Pond in the south-east of the city was surrounded by bars run by Sogdian immigrants, crammed with rowdy drinkers and dancing girls in diaphanous gowns.

An appreciation of fashion and material culture is of vital importance for the novelist or historian setting a scene, particularly in an age like the Tang, where the women adorned their faces with slashes of bright scarlet like kabuki actors, and where the most glorified female form was one that had internalised all the prosperity and wealth for which the age was famed – Tang men were chubby-chasers who liked big, beautiful women. Whenever there’s a Twitter storm about a Tang-historical TV show, invariably starring stick-thin actresses, I’m tempted to disrupt things by asking innocently: where are all the fat girls? But Chen points out that even this was a fluctuating trend – she quotes from the 9th-century art critic Zhang Yanyuan, who points to a tendency towards the voluptuous in artistic representations of Tang women along a time-line that more or less matches the rise of Empress Wu. The famously chubby Yang Guifei, contrary to the assertions of many later writers, was not a plus-size trend-setter, but a woman who fitted a new standard of beauty established a generation before she was born.

The mid-Tang dynasty saw an immense rise in the power and influence of women. Chen charts those moments where both wearers and observers of fashion used clothing choices to mark moments of rebellion or transgression, beginning with the moment when Empress Wu’s notoriously chippy daughter Princess Taiping turned up at a banquet dressed like a general. Clothing, notes Chen, was “perceived to be constitutive of the person.” We are what we wear.

Nor is this mere set-dressing. Curators at Luoyang Museum have created a massive pictorial genealogy of Tang hair fashions, exacting enough that archaeologists can often date a grave to the nearest decade from the hairstyles on the statues inside it. Fashions reflect not only material culture, but political changes, as evinced by the sudden rise of hufu (“barbarian garb”) among ladies who wanted to show off by wearing trousers and jackets with lapels. Chen runs with this idea, charting the prevalence of certain kinds of skirt or colour in tomb figurines from different decades. Her illustrations, on which many of the women’s faces have been scratched out while their clothes remain, serve to demonstrate the immense value of unexpected metadata in otherwise “spoilt” materials.

In an era where clothing was thought to be a reflection of reality and harmony, dressing decisions could be announcements of bold changes in status or grabs for power – Tang dandies literally dressed the part, even if the part was aspirational. The first Tang emperor decreed that a woman’s clothing should be selected in direct relation to the status of her father or husband. By the time of his daughter-in-law, Empress Wu, that had gone right out the window. By the time of her grandson, Xuanzong, even court ladies were going out in “barbarian clothes” – later taken as an omen that the dynasty had been corrupted.

Chen takes her account beyond the height of Tang fashions into the miserable scrabble for survival after the revolt that brought down Xuanzong. Fashion became a battle-ground for conservatives, with a backlash against women that sought to regulate their hemlines, while poets juxtaposed the image of the beautiful clothes of the aristocratic lady with the unkempt, dishevelled appearance of the weaver-girl who has made them. It’s a fascinating snapshot of changing styles and attitudes at the height of the Silk Road.

The “Serpentine Pond” pond is still there, by the way. These days, it’s part of a medieval theme park in Xi’an called Tang Paradise, where there are many parades, fire-breathers and kung fu displays: a lot of dancing girls, but lamentably little Tang-dynasty cleavage. People can’t leave well enough alone.

Jonathan Clements is the author of A Brief History of China. Empire of Style: Silk and Fashion in Tang China is out now from the University of Washington Press.