Tailoring has been loosening up in the past few years, and it’s easy to see why. Softer, more generous cuts provide a flattering silhouette without the starchy formality. What’s sometimes overlooked is the importance of a relaxed, gently aged fabric, which is key to the effortless, worn-in charm of the best casual suits and separates. That’s where garment dyeing comes in.

Garment dyeing entails colouring clothes after they’ve been cut and sewn. Ordinarily, fabrics are woven and dyed by the roll, but if you make up a shirt or suit first and then apply the dye, this softens both colour and texture, giving new pieces the rumpled elegance of vintage. It’s an innovative way to transform the feel and finish that upends the typical manufacturing process. At the same time, it’s a delicate and risky art. You have to plunge the finished articles into a vat of dye without ruining their feel or shape. Like making gin, this is not something to try at home.

If tie-dye became the iconic colouring technique of the 1960s, thanks to its chaotic, home-brew rainbow aesthetic, the invention of modern garment dyeing in the 1980s presented an industrial, highly technical alternative. As anyone who’s ever accidentally shrunk a sweater in the wash knows only too well, fabrics react to water in unpredictable ways. Add the challenge that nylon or silk thread, cotton, linen and cashmere all shrink at different rates and behave differently with the same dyes, and the problem becomes clear.

The pioneer who solved this dilemma was Italian designer Mr Massimo Osti, best known for his brands C.P. Company and Stone Island. His innovation was to understand and exploit these behaviours, rather than fear them. By dyeing at 90°C, he encouraged rather than resisted the shrinking and made it part of the design process. Using the differences in dye resistance between natural and synthetic fabrics, he created rich, tonal colour palettes, as seen in the iconic Mille Miglia goggle jacket, with its mix of specially treated linens and polyamide. He even hired a company chemist, Mr Giuliano Balboni, and developed new fabrics such as Nycra, a nylon-Lycra mix designed to endure garment dyeing without losing its stretch. Mr Osti died in 2005, but his legacy can still be seen in everything from cotton-piqué polo shirts to jackets made from technical fabrics.

The benefits of the new technique were immediately clear. Garment-dyed pieces have a softer finish and a subtle range of colour depth. Colours are palest on the exposed edges and richest in the crevices, where dye accumulates. This means that, unlike most clothing, colour follows shape. It’s like washed denim in reverse. Rather than crisp uniformity, you get a garment that feels lived in from day one. And because dye seeks out differences in the surface of the cloth, it highlights stitching, fabric choice and finishing.

Garment dyeing continues to appeal to designers today because it grants creative control over colouring and finishing. Italy remains the leader in this difficult art and two Milanese brands have been especially successful in applying the tintura in capo technique. As Aspesi’s sophisticated casualwear demonstrates, the natural partner for garment dyeing is cotton. It works harder, ages more gracefully than any other fabric and acquires fades and patina from sunlight and daily wear. In workwear-influenced pieces, garment dyeing adds surface interest and texture by fading and slightly puckering the seams. In these tapered cotton-twill trousers, the technique is combined with stone washing to give a double measure of out-of-the-box ageing and character.

If we’re talking tailoring, it’s family business Boglioli that excels in the field, producing garment-dyed jackets and suits. Mr Mario Boglioli attributes the innovation to his brother, Mr Pierluigi Boglioli (namesake of the brothers’ newer brand, The Gigi). Boglioli’s signature K-Jacket is the classic Milanese interpretation of soft tailoring. It retains the refinement of classic Italian menswear, but is lighter and a touch shorter, designed to wear more like knitwear. These jackets may be soft, unlined and unstructured, but it still takes some nerve to put fine tailoring in a washing machine.

The results speak for themselves – finely balanced tailoring, perfect for summer weddings and evening events, crisp but not formal, refined but not stuffy. The secret to wearing a cotton suit is that it should look lived in and cherished. A crisp navy business suit exudes presence, but holds people at arm’s length. Cotton suits should welcome you like an embrace. While the temperatures remain high, also consider Boglioli’s designs in linen and airy hopsack wool, but keep an eye out in the autumn for the return of its spectacular garment-dyed cashmere jackets and flannel coats.

Garment dyeing takes clothes around the block a few times. Even before they’ve been worn, they have endured more heat and friction than a year spent playing squash. But, like an experienced sportsman, their past trials allow them to relax. Garment dyeing gives casual pieces a vintage character with none of the accumulated fatigue. And it gives refined but stiff suits the tailoring equivalent of a couple of drinks. What’s not to like?