But between discussing mid-20th century and contemporary mores on sexuality, she's found time to discuss the impact of cassis and chypre top notes, with light incursions of musk - and, furthermore, to sound engaged and interesting.
We met at the Cannes Film Festival, during which, you may recall, the tabloids gleefully outed Blanchett as a bisexual after she allegedly told a reporter from Variety she had had many relationships with women. "What I actually said was something like, 'I've had many relationships with women, but if you mean sexual relationships, the answer is no.' Somehow the last bit got left out." She's less perturbed by the journalist - "we had a great time" - than by what she calls "the toilet-door nature of the internet".
She still plays the game, though. It helps that her relationship with Giorgio Armani goes back the best part of a decade. They met in 2006, shortly after she'd been nominated for an Oscar for playing Katharine Hepburn in The Aviator. She wore a bronze Armani Prive column gown to the Oscars the following year, and a jewelled, pale gold Armani Prive dress when she collected her Oscar (her second) for Blue Jasmine in 2014 - the result of Woody Allen's non-interventionist direction. Also of note: Armani's generous sponsorship helped Blanchett and her husband of 18 years, writer and director, Andrew Upton, run the Sydney Theatre Company, where they were co-artistic directors from 2008 to 2013.
Cassis and musk appear to have been notably absent from Upton and Blanchett's working environment at STC. "Our office there is open plan - not remotely glamorous. Most of our programme planning happens in the disabled loo. That's our only private space."
Loos are becoming a leitmotif in this interview. Later, when her entourage come to sweep her away to the evening's events, she'll look beseechingly at them and ask if she has time to pee.
Upton is in Cannes somewhere. He was also with her a fortnight earlier for Armani's 40th anniversary celebrations in Milan. That month was definitely his stint as Mr Blanchett. How have they managed to work together and remain married?
"I know - people look at us in horror. We share an office, an email address - which makes it impossible for him to have an affair, even though I try not to monitor him.
Andrew was really the first person I'd met that I could talk to in an uncensored way about everything. He's incredibly well-read and had this sense that I just do not have - but our eldest son [Dashiell, now 14] has - of reading a script and understanding what's coming next. Working together with the theatre company was a natural extension of that."
With Upton's tenure at STC ending, they're planning to relocate to America with their three sons and Edith, the tiny daughter they adopted earlier this year. I wonder whether the Australian tabloid press, by all accounts even more rambunctious than the British, has finally driven them away.
"It's true we're a smaller population, so we've got fewer people to feed on. But we live in a very private suburb. We know we can go to certain restaurants and parties ... It sounds banal, but I love cooking. My little one has gut issues, so my latest challenge is to try to cook things the kids will eat without sugar. I've gone a bit Heston Blumenthal, going through all the chemical compositions with my son, trying to work out how you make things sweet without sugar."
She makes it all sound so normal. But it's hard to know how any actress stays sane. It's not just the life, it's the craft. Playing Blanche DuBois on screen allegedly tipped Vivien Leigh over the edge. Blanchett took on Blanche three seasons in a row - in Sydney, Washington and New York. Then came the Blue Jasmine re-rendering of the Tennessee Williams original.
"Woody kept saying 'this is not Streetcar', but Blanche was clearly a touchstone for me." It took its toll. When the producers wanted the stage interpretation of Streetcar to transfer to Broadway she declined. "I didn't think I could play her for another three months. I'd lost a lot of weight and my hair was falling out."
With three sons and a daughter, she's ideally placed to ... "screw her up?" she quips. I was going to suggest you're in pole position to observe gender stereotyping, I say. "People have been talking a lot about that recently," she muses. "Maybe it's because of the subject nature of Carol, and a general trend in society. But we won't be experimenting with our daughter."
Regarding gender stereotyping, I have to ask Blanchett about clothes, because she's deployed them so brilliantly throughout her career. "I spent my first pay cheque after drama school on an Armani suit, which I've still got - and wear. Clothes are a huge part of the acting process. In a way they're the most creative aspect, because you don't always get a lot of rehearsal time, so the costumes can help coalesce all kinds of ideas. Todd [Haynes, the director of Carol] made a point of attending the hair and makeup sessions - all good directors do."
For someone whose red carpet choices have been as bold and eccentric as her roles, she says decisions are made quickly. Despite claiming that her favourite wardrobe piece is trousers, she can certainly work a ball dress.
"The Giles Deacon I wore in Cannes [15 metres of silk, print inspired by a fax machine] was an easy, instant pick," she says. "I saw it on a shoot and thought, 'Where else could you wear that?' When you decide by committee it kills the spontaneity. I probably get shocking reviews on the red carpet, but I don't read them."
All actresses say this, and if I believed any of them, it would be her. "Of course I read the news," she says. "But if I see anything about me, I just look at the pictures. I'm very superficial."
She still finds assessing her performances hard. "The first time you watch yourself in any role, it's excruciating. The more you do it, the more you can treat it objectively and make comments like, 'Oh, that was a bad choice.' But it's never easy."
Although latterly actresses in their late 40s and 50s (Blanchett is 48), seem to be finding more satisfying roles - see Streep, Kidman, Scott Thomas - the scrutiny on their looks remains intense. When I got back to London after interviewing Blanchett, the question all women asked was: "How's she looking?"
The complex answer is that she has an idiosyncratic beauty that can look masculine one minute, fragile the next. Even without the wigs and makeup, she could probably morph from Elizabeth I to Bob Dylan and - her next role - Lucille Ball. It all seems to be in her eyes.
The simpler answer is that she looks precisely how you'd want a sane, intelligent woman to look: animated, with crow's feet when she smiles. She's wearing another Armani suit - this time white, with grey stilettos.
Blanchett clearly takes care of herself, stays out of the sun, keeps slim rather than bone-thin, uses copious amounts of SKII, the upmarket skincare she advertises, works with the best hair and makeup teams (the makeup artist Mary Greenwell is godmother to Edith, testament perhaps, to how much time actresses spend with their beauty squadrons), but she's far too smart to neuter the tools that won her two Oscars.
- Canvas, Telegraph
