One of the highlights of this year’s Brighton Festival, curated largely via web chats and long-distance phone conversations by Aung San Suu Kyi, is Kutlug Ataman’s silent film installation Mesopotamian Dramaturgies. The leading Turkish artist, a favourite of international biennales and arts festivals, has taken over the town’s Old Municipal Market to show two multiple-screen works. And in this vast, disused space, as gloomily dark and dank as it is cavernous, we find the perfect backdrop against which Ataman’s films shine.

Max Bill might be the missing link in modern art. He died only in 1994, yet he studied at the Bauhaus in Dessau in the 1920s, taught by Josef Albers, László Moholy-Nagy, Paul Klee and Kandinsky. It is hard to imagine that someone who was working at full strength less than 20 years ago could have a past that is so strongly entwined with these legendary names – hard to imagine, that is, until one looks at the work displayed in this fine retrospective, which even so manages to encompass only five decades of a nearly seven-decade-long career.

“As a student at Glasgow School of Art I used to visit the amazing anatomy, zoology and ethnographic collections at Glasgow University,” says Christine Borland. “I couldn’t understand why I was so intrigued, except for the question of how something so awful – so dead – could also be so beautiful. I was trying to unpick my responses, to understand how beauty and death could co-exist.”

It is now 37 days since Ai Weiwei was detained at Beijing international airport by the Chinese authorities. His family and friends have heard nothing since. His lawyer, to whom under Chinese law he must have access, was arrested as well, and since his own release he too has heard nothing. Officially, unless charges are brought today, the period in which he can be held without charge expires. And yet, where is Ai Weiwei? The whereabouts of Ai Weiwei the man are unknown. In London, however, Ai Weiwei the artist makes two stellar appearances.

Freud’s West Hampstead house is tied up in a cat’s cradle of thick rope. The rope is the same colour as the brick, a deep orange but with a sheeny lustre. It makes the house look not quite real, a Brobdingnagian doll’s house transplanted to this unsuspecting corner of leafy west-London suburbia. It’s an uncanny impression heightened by the pristine condition of its squat, many-windowed façade.

Who or what is Jean-Marc Bustamante? This, surely, is the question we are supposed to ask of this artist of the affectless, who has skated in his three-decade-long career across the genres – first photography, then Minimalist sculpture, then a merger of the two, and for the last few years these shockingly vivid “paintings” (I use the scare quotes intentionally) on Plexiglass.

Chantal Joffe first came to attention in the 1990s with a series of paintings reproducing pornographic images, using a typically thick, impastoed paint and heavy brushstroke to depict hard-core acts in a defiantly flat, emotionless tone. Since then she has moved on, first to paintings reproducing fashion photographs, and now, in her new show, to images that re-imagine 19th-century aspects of femininity and femaleness in a 20th-century mash-up of psychology, anthropology and literary and art history. This sounds, unfortunately, rather less appealing than it is, for the images themselves mostly reward attention, even if the theoretical statements behind them have become increasingly divorced from meaning.

Weeds, memorably, have been described as merely being plants that grow where we don’t want them. Walking through the Wellcome’s fine new exhibition, we can conclude that the “dirt”, too, is merely material appearing out of its appropriate location. One man’s waste is another man’s fertiliser; one civilisation’s dust-heap another’s city foundations. Children first planting a window box learn that “dirt” is alchemy: stick in a seed, out of the dirt comes dinner.

There have been exhibitions, indeed even a whole museum, dedicated to cleanliness: the Deutsches Hygiene Museum in Dresden, for instance (image 9), which was founded for the purpose of public education in hygiene and health, but which later embraced and diffused racist theories during the Nazi era. Yet there haven’t been many – or any, as far as I’m aware – devoted entirely to dirt. It’s all around us, yet historically we seem to have considered the subject unworthy of serious cultural examination. And the reasons for avoidance are just as interesting as the filthy matter currently under the microscope at the Wellcome Collection (see theartsdesk's review).

As a young man searching for a way to make a living in Paris, Antoine Watteau briefly tried his hand at engraving fashion plates. He seems to have had a natural affinity for cloth and drew its folds and creases with such apparent ease that you can almost feel the slipperiness of satin and hear the rustle of taffeta as it moves with the body. This was just as well, since he didn’t attend the Academy where students did life drawing and learned anatomy.