Grand feu is almost a lost art in luxury watchmaking. The delicate technique that heats layers of enamelling powder in an oven at temperatures up to 1,000 degrees Celsius to achieve a subtle patina is extremely costly and time-consuming. Yet, to untrained eyes, the discreet decorative effect could easily be overlooked compared to otherwise lavishly decorated skeletonised or diamond-paved dials.

The technique has been revived by high-end watchmakers from Patek Philippe to Jaeger-LeCoultre and Vacheron Constantin. Collectors and connoisseurs are ravished by such hidden gems that define luxury in a much more discreet manner.

Details such as grand feu enamel, secret watches and concealed complications, including tourbillons, have been included in high-end watch offerings the past two years, reflecting a growing appetite for subtle luxury.

"It's very difficult to make something simple," says Stephen Forsey of luxury independent watch brand Greubel Forsey. "Collectors are evolving. They have a deeper understanding of the subject and are seeking out refined and [simple] designs."

Greubel Forsey's latest novelty Tourbillon 24 Seconds Vision, for example, features a grand feu dial heated in the oven eight times and a dome housing the inclined tourbillon visible only on the caseback. The elegant piece was a rare addition to the brand's avant-garde portfolio.

Veteran watchmaker Laurent Ferrier agrees and says: "Luxury is not to show off and say, 'look at my watch - it costs 20,000 Swiss francs [HK$156,600]'. It's to let your watch do the talking. Beautiful, classic and discreet, with special movements to show a friend or two who can also appreciate, to me that's the real definition of luxury."

Ferrier's ultra-exclusive Galet Secret Tourbillon Double Spiral can set you back HK$2.55million for the white gold version. At this year's prominent luxury watch fairs, including Salon International de la Haute Horlogerie (SIHH) and Baselworld, the sentiment towards more simple designs is evident.

"Compared with last year's SIHH, fewer new references and collections were introduced," says Jeffrey Yau, CEO of Europe Watch Company. "Extravagant masterpieces were not prevalent. The trend has become more down-to-earth and classical, focusing on sophistication and craftsmanship."

Emperor Watch and Jewellery chairwoman Cindy Yeung agrees. She describes the transition in trends from "over-the-top designs and prices" towards more "subtle" novelties.

Instead of launching jaw-dropping, exceptional grand complications, luxury watchmakers are introducing subtle luxury collections that highlight craftsmanship and heritage - think Cartier's all-new Clé collection, which adopts a more minimalistic and streamlined design. Piaget's Altiplano series launched in 2013 featuring ultrathin calibre and discreet crafted dial continues to be one of the maison's flagship products.

"Luxury is definitely more than what meets the eye," Peter Cheung agrees.

Cheung recently started his own branding consultancy, Peter Cheung Asia, after working with luxury brands such as Christian Dior, Versace and Van Cleef & Arpels.

"Before, [Chinese customers] were looking for more visual identifications of luxury, but now they appreciate the brands for their craftsmanship, heritage and bespoke aspect."

Patek Philippe launched an unexpected reissue of its much sought-after Annual Calendar Chronograph not in platinum but stainless steel last year.

"Nobody expected us to come up with a steel version," says Philippe Stern, CEO of Patek Philippe. "I think it's important to remember that watches shouldn't intimidate but make the owner feel confident. This is the know-how - we have technicality and also the understanding of our customers."

German watchmaker A. Lange & Söhne also highlights attention to details from product design to customer service which flaunts the brand's subtle yet luxurious DNA.

"You'll never see a bling-bling piece coming from us unless for bespoke orders," says Wilhelm Schmid, CEO of A. Lange & Söhne. "A lot of effort goes into the smallest details."

The brand's grand complication launched this year - Zeitwerk Minute Repeater - implements a complicated mechanism that freezes the decimal reading when the minute repeating function is activated so the owner will see and hear the time consistently.

The shifting trend obviously has much to do with the slowdown of luxury consumption in the mainland Chinese market and political and economic uncertainties across the globe.

"There are a lot of uncertainties, either political conflicts or natural disasters," says Jerome Napoleon de Witt, president and founder of DeWitt Watches. "DeWitt's concept X watch and vertical tourbillons are exceptional pieces that have very strong images. But we can't sell 2,000 pieces of X watches a year. I feel [customers] are shifting towards something clean, classic, subtle but still with luxury details."

Luxury conglomerate Richemont, which owns watch brands such as Cartier, Piaget, Jaeger-LeCoultre and Vacheron Constantin, stated in its annual report released in May that its operating profits for specialist watchmakers dropped from €778 million (HK$6.7 billion) last year to €730 million this year - a more than 6 per cent plunge. The report highlighted difficult trading environments in Hong Kong and Macau.

The turbulent market climate isn't the only reason behind the subtle luxury trend. A new strain of sophisticated collectors is growing on the mainland and in Asia-Pacific who are moving on from over-the-top extravagant designs.

"The past 10 years have been an incredible boom of luxury in China and Asia-Pacific. I think that cycle has ended," Cheung says. "Europeans have references of luxury lifestyle to hundreds of years but for China, those 10 years were almost the equivalent of those hundreds of years. Customers' sophistication level has grown rapidly."

Rapidly changing client demographics are also affecting how luxury watch brands communicate their stories. Celebrity-endorsed campaigns are giving way to documentaries following veteran watchmakers and artisans in century-old manufactures and ateliers. Retrospective exhibitions showcasing brands' rich history and know-how are commonly held by luxury watch labels.

"Brands have changed their strategy to story-telling," Cheung says. "I think they have to work even harder. It's easy to communicate something that's logo-centric but with subtle luxury, it takes time to get the consumers' attention."

The growing popularity of subtle yet luxurious timepieces is also putting independent watchmakers such as Laurent Ferrier, Lang & Heyne, Speake Marin and H.Moser & Cie in the spotlight.

"It takes a long time and lots of effort to create subtle timepieces with unique design and exceptional craftsmanship," says Piano Chow of Lavish Attic - a luxury retail boutique with a focus on independent watch brands. "It sets a barrier to [mainstream] brands because they are bounded by commercial results."