The title of the show - The Secret History of the Mondrian Fan Club II, Mondrian in London - might suggest that the main theme is Mondrian. But not a bit of it. Pride of place goes to the bubble machines. There they stand in the middle of the room, four spectacular perspex structures, each more than ten feet high, and each resting on a plastic base in the appropriate Mondrian colours - red, yellow, blue and white. The machines work completely silently: white foam creeping gradually up the perspex walls to the top, where it is slowly squeezed from holes and slithers down the sides to form great crenellations at the feet of the machines.
Bubbles are David Medalla's hallmark. In 1963, he made Cloud Canyons - tall columns of wood and Formica that slowly extruded great thick snakes of soap bubbles. In 1966 came Cloud Windows - fibreglass squares that slowly extruded great thick snakes of soap bubbles.
In 1971, there was Cloud Discourse - another column that slowly extruded great thick snakes of soap bubbles, not to mention Cloud Fruits and countless other memorable extrusions of great thick snakes of soap. Of course, there have been other things too -the sand machines, the mud machines, the smoke machines, the project to lift the Great Wall of China on to the moon - but, essentially, Medalla is Mr Bubble.
Now, suddenly, he is flavour of the month.
It is 12 years since Medalla's last solo show in London, but as 1994 comes to an end, there is the Mondrian show and a New Year's Eve "happening" and a new edition of Signals, a Sixties avant-garde magazine which Medalla helped to edit, and an appreciation of Medalla, Exploding Galaxies, by Guy Brett, a former art critic of the Times, who believes the artist has never received the recognition he deserves.
Medalla's present gallery is also a bubble of sorts: it is in a grimy old warehouse in east London which could easily be mistaken for a grimy - but interesting - warehouse in the East Village in New York. Three floors up is a large room with metal-framedwindows and brick walls painted white. Here Medalla and his friends are preparing for Mondrian in Excelsis, a "non-linear" performance which, at the stroke of midnight on 31 December, will bring in the new year.
The bubble machines are off, emitting not so much as a burp. Yet the floor is wet from previous bubblings, with rivulets of soapy water winding across the gallery and puddles collecting in dips in the cement. Hopping across the puddles - squelch squelch squelch - comes David Medalla, in a grey suit that forms in folds over his shoes. The suit, I learn later, has been put on for my benefit. Normally he wanders around in big boxer shorts with outsize shoes, looking like a Dufflepud from CS Lewis's Narnia books.
But today he has on a suit, many, many sizes too big and somewhat glossy. And the suit, along with the upright hair cropped in a circle round his head, makes him look small and slightly surprised. In fact, Medalla is small, a delicate, fine-featured man,who in his youth was clearly a great beauty and still today - he is 52 - has a certain ravaged distinction. This is a face you would never forget: the soft bug eyes, the high cheekbones, and, not least, the peculiar colour. For the upper part of Medalla's face, all the way from his wonderful eyelids up to the roots of his hair, is blue. A very familiar blue, very reminiscent of, of, of...the same blue as the blue squares in the painting on the wall. Aha! Medalla is hospitable. He beckons me over to a chair, kindly warns of the puddles and orders the bubble machines to be turned on. While they gently begin to ooze, Medalla talks. He has lived in Britain since the Sixties, but his English is still heavily accented, and he pulls at his words in the wrongplaces. He says advertISing and EXpensive.
The bubble machines, for example, are EXpensive. And every bubble machine, he insists, is different. Different sizes, different shaped exit holes at the top, and different kinds of air pumps. And each of these variables, of course, makes for a different sort of bubble. The bubble machines in this exhibition are "very slow and subtle because partly it is the Mondrian spirit - very contemporary".
Originally he would have liked to have had the middle of the bubble machines illuminated: "The square would be a blue light and a red light and it is in total darkness and it just glows, you see. It becomes redder and redder and redder. Then it changes into blue blue blue blue and then, you know, it starts palpitating ... And it will be on a bigger scale - that is if one got more money. In another place. If, say, the Pompidou Centre commissions me..." And although Medalla's voice trails off here, the blue blue blue blue fingers continue to rummage in the air.
By this time the foam is beginning to slide down the sides of the perspex, forming clouds of fluff on the ground. Medalla gets up from his seat. He must, he says, show me round. He points to the abstracts on the walls, which represent the four seasons and the four cities in which Mondrian lived. There is Amsterdam (the painting with the blue squares), Paris, London and New York.
And then he goes on - maybe one day he would be able to do not the four cities, but the four rivers, and in front of each river would be a Plexiglass covering with a mobile part and then moving lights, glancing off the surface of the plastic, moving likewater... And Medalla's voice trails off as the hoary-breathed monster, EXpense, blows out another brilliant idea.
Nearby stands a makeshift partition, and behind it are mattresses with scrolls of twisted bedclothes, and piles of books, and half-finished paintings and still more milk bottles. Does he live here? No, he lives in Bracknell, a new town in Berkshire wherehe has been artist-in- residence at the South Hill Park Arts Centre. Medalla insists that Bracknell is a very nice town, if not very exciting. And the council, even though people may laugh at them, are very good and have given him a little place there. Later, when he has dropped his guard, Medalla describes the little place as "a hole".
``By the way, I am not poor. I go from one extreme to the other. Unlike most artists I don't really care for fame that much. I've made a lot of people famous. I don't care for fortune that much because, strange as it may seem, I think I know 20 of the richest people in the world."
Yes, and the present exhibition is funded by a friend, the Littlewoods heir James Moores. But Medalla won't mention him by name and claims to have "no idea" what the show cost.
``Nowadays artists do an artwork and then it is like a consumer thing, but I am just not that kind of artist.'' Instead, he says, he prefers to take his time. Just, he says, like Mondrian. "Even small paintings, he worked on them for 25 years. Maybe thatis why he was so poor."
Medalla's enthusiasm for Mondrian started early in life. He was a child prodigy, one of 17 children from a wealthy and eccentric family in Manila. By the age of ten, he had published poems, translated Hamlet into Tagalog, and spent nearly a year living in the northern Philippines with members of the Igorot and Ifugao tribes who, he says, still hunted for the occasional head. Rather unusually for a prodigy, Medalla talks of his childhood as a supremely happy time - with his own tree houses and puppet shows and the happy companionship of two brothers who also happened to be prodigies.
When he was 12, Medalla enrolled at Columbia University in New York. It was then that he saw his first Mondrian, Broadway Boogie-Woogie, in the Metropolitan Museum of Modern Art and was suitably bowled over.
A year later, Medalla, wanting to concentrate on art, dropped out of Columbia and returned to Manila where he set up a bohemian cafe for which he painted his own version of Broadway Boogie-Woogie, which, he says, was sadly inferior to the original. Later, after extensive travelling, Medalla gravitated to Paris and London, and became quite a figure in the Sixties, with his own gallery, his own magazine, his own dance troupe (the Exploding Galaxy), and a commune in Balls Pond Road, in Islington, which aroused the prurience of the News of the World.
It was during the Sixties that Medalla had his formative experience with bubbles. One day, looking at the sky from the summit of Arthur's Seat in Edinburgh, he saw in the clouds the white bubbles of a coconut milk delicacy his mother used to cook when hewas young.
The clouds also brought back a less pleasant childhood memory - of a wounded Resistance fighter dying in his parents' back garden during the Japanese occupation of the Philippines. "He could hardly speak and as the sun was rising up - it is so dramatic -his mouth was bubbling, you know, bubbles mixed with blood...
"After the thing in Edinburgh, I started to think maybe art could be made out of insubstantial things." And that is what Medalla has done, more or less, ever since, although many of his statements in conceptual art, either because of their hideous expense, or their outrageousness, or both, have remained in the realm of ideas. For when you talk to Medalla, he is always hoping for a multinational satellite link, or a laser, or he's suggesting that the Hayward Gallery provide free vintage wine to the public from tubes hanging down from the ceiling, or he wants to invite in the homeless from Blackfriars Bridge to create an installation, or he has a plan for a "Flying Mondrian" - a "sky painting" made up of red, blue, yellow and white blocks of light projected from aeroplanes. "Somebody in Hawaii is organising it. He has already talked to eight people with private planes. Now, if somebody could photograph it from a satellite..."
I have heard this before. Hasn't the Flying Mondrian idea been around for some time? Medalla sighs: "Ahhh. We were supposed to do it this month, but I told him we can't be in two places at once. Not yet. In time there will be a virtual me..."
Midnight approaches on New Year's Eve. Friends and helpers are still hard at work. A woman in flowing hair and evening dress carries in a last bucket of water for the bubble machine. A helper is sent down to the street to collect material for the mud machine ("Mud. No dog poo"). One friend has made a beautiful paper conical hat with Mondrian squares of colour and curly edges for Medalla to wear for the performance. Another is standing guard over his creation, a spread of exquisite snacks in Mondrian colours with an "M" picked out in chrysanthemum leaves.
And where is Medalla himself? When he finally emerges, he is wearing a very large long velvet jacket, a large, long shirt with big white clock faces, and large, long shuffly shoes. He has shaved his head for the event but has left a small chuff of hair standing up in the middle. He is no longer blue.
Medalla begins the performance by announcing that the projector isn't working, so the film-in-progress will not be shown. But that, he says, "is performance art for you". Then there is a manifesto, Etica Espressiva Universale, which Medalla tries to readaloud and which seems to be all about humanity existing as a single oneness of trees and trains and computer terminals, only it is in Italian, a language which Medalla can only read very approximately. Soon he abandons the effort and moves on to a shadow puppet play about Mondrian's time in London. But this also has a few hitches: the makeshift screen falls repeatedly and the torches providing the shadow are never in the right place, and the man who is meant to be doing boogie- woogie riffs on the guitar begins late, and the accompanying video of boogie-woogie dancing has been shot by someone who keeps filming the pavement instead of the dancers' feet.
So it continues: missed cues, bumbling renditions, Medalla striding up and down the central aisle with the conical Mondrian hat and a gold cloth wrapped over his shoulders, saying loudly, as if it were a recommendation, "this is completely unrehearsed, completely unrehearsed".
And come the stroke of midnight, he is standing solemnly on the top of a ladder in his conical hat and holding a cassette recorder playing Himalayan mountain music. Meanwhile the audience, who are all embracing and refilling their drinks and throwing little paper planes round the room, pay not a blind bit of notice.
I sit transfixed, completely mystified. How could anyone in their right mind ever have paid Medalla to put on such a performance? All the ingenious ideas and the wonderful little touches - the beautiful conical hat, the exquisitely composed canapes - all lost in the shambles.
But after the performance his friends just laugh good-naturedly. And no doubt this is partly because tonight is New Year's Eve and partly because Medalla is such a likeable man. But it is hard not to think that, if only he hadn't been so indulged by his friends, if only someone had taken him in hand earlier and made him marshal his resources better, then things might have panned out differently.
But Medalla's concept of himself is old- fashioned. This is no manipulator of a market place, but an "Artist" - the dreaming, impractical, propertyless sort who keeps going even if that means living in Bracknell and getting cold at bus stops and making installations out of old egg boxes and string. Casual members of the public who wander into Medalla's gallery may question the value of his work. They may tire of his paintings, they may detect a certain insubstantiality in the bubbles and mud. But Medalla himself is absolutely convinced. His belief in his work is utterly genuine, and completely consuming. And that is his great saving grace.
When I was interviewing Medalla, the photographer asked him to pose by one of the bubble machines, then in full froth. Medalla agreed. He waded up to his knees in bubbles. Then, at the photographer's suggestion, he rested his arms on a ledge of the machine so that soon he was up to him elbows in foam. But Medalla didn't seem to mind. He fondled the bubbles: "You see, life is like that. It's beautiful, beautiful. The shape is so elegant. One day they'll make buildings out of it...you know, new technology..."
Afterwards, Medalla walked back to his seat. Splat splat splat. He had a blob of bubble on his chin, and white mittens of foam covering his hands and great bellbottoms of foam collected in the folds of his trousers. As he talked, the foam drooped and disappeared into dark soggy patches on his clothing. Medalla's feet must have been very damp, but he went on oblivious: junctions of time and space, symbolic structures, Buddhist texts, if only one had a satellite... Soon his nose was blocked. Every once ina while, with increasing regularity, he sniffed. David Medalla's latest show is at 3rd floor, 55 Gee St, London EC1, 2pm-8pm (not Mon) to 14 Feb