Yves Klein's (in)famous 1958 presentation of aura-infused gallery space was accompanied, in the same year, by a further foray into the realms of the intangible.
His Zones de Sensibilité Picturale Immatérielle (Zones of immaterial pictorial sensibility) (1958-1962) involved the exchange of 'charged' empty space - represented by a cheque-like certificate of ownership (below) - for gold.
Purchasers of his immaterial zones were then given the option of completing an elaborate ritual (left) in which, if the certificate was burnt, Klein would obligingly throw half of the bullion into the waters of the Seine (the remainder was used to help produce a series of gold-leafed canvases).
Robert Rauschenberg, whose White Paintings had already proved instrumental in the quest for aesthetic absence, was likewise one of the first American artists to engage with the (almost) entirely dematerialised art object.
Invited to contribute a portrait of Parisian art dealer Iris Clert for a 1961 show at her renowned, eponymous gallery, he sent a telegram simply stating 'This is a portrait of Iris Clert if I say so.' (below).
Of all the artists concerned with dematerialisation of the artwork, Robert Barry's formulations of absence are among the most consistent (and consistently interesting).
His 1969 Inert Gas series (above) saw the artist empty canisters of krypton, xenon, argon and helium into the Californian landscape.
Documented only through anecdote and photographs, Barry conceived of his actions as a cyclical, almost ritualistic manoeuvre:
"The important part of making the piece was that I simply returned the gas which had been taken out of the atmosphere, stored in a container in a measurable volume, and then would be used commercially. ... thus creating a kind of cycle."
As Barry has also pointed out, his "... attempt to use material ... which is an undetectable material, you can't smell it or see it" was key to his subsequent embrace of entirely conceptual artworks: "It was one of the last works that I did in '69 where I actually used physical material."
Accordingly, his contribution to the 1969 exhibition 'Prospect' consisted solely of a catalogue interview in which he describes a physically absent 'collaborative' work:
"The piece consists of the ideas that people will have from reading this interview... The piece in its entirety is unknowable because it exists in the mind of so many people. Each person can only really know that part which is in his own mind."
In similar vein, his 1969 Telepathic Piece at Simon Fraser University, Vancouver, consisted of a printed declaration that "during the exhibition, I will try to communicate telepathically a work of art, the nature of which is a series of thoughts that are not applicable to language or image."
Right: Robert Barry, list of 'telepathic works' created from April to May 1969
Other works created in 1969 (which, if the term can really be applied here, was a particularly productive year for Barry), included the following, beautifully understated contribution to the sixth issue of Vito Acconci's magazine 0-9:
The space between pages 29 and 30 / The space between pages 74 and 75
and his 90mc Carrier Wave (FM), consisting of radio waves generated by an FM radio transmitter.
Installed in gallery space but hidden from view, the waves produced tones of varying intensity when amplified through a transistor radio, also making the piece one of the first to posit that sound, as well as objects, can sculpturally define space.
Andy Warhol's Invisible Sculpture - an empty plinth bearing the label 'Andy Warhol, USA / Invisible Sculpture / Mixed Media' - was unveiled at the New York club, Area, in 1985.
It's usually claimed that (in a gesture reminiscent of Yves Klein's exhibition of personal aura) Warhol briefly ascended the dais in order to infuse it with his own creative genius, but this 'addition' to a work conceived as essentially empty is probably redundant.
In fact, the artist had been pondering the creation of invisible sculpture for several years, having already produced a temporary installation described in the memoirs of Ronnie Cutrone, a painting assistant to Warhol from 1972 to 1983.
Cutrone recalls how "Andy wanted to make the Invisible Sculpture. I don't know what the inspiration for that was. He may have watched 'The Invisible Man' one night on television. So ... we got out the Yellow Pages and found burglar alarms, different systems. Some with sound, some with light beams....We mounted these burglar alarms on brackets all around the perimeter of the big room in the middle of the Factory.... And we aimed them all at the center of the room where nothing existed. If you walked into the room and you hit this center point, all of these alarms would go off. You'd have every different kind of sound; chirping, booming, buzzing."
Cutrone rightly goes on to describe Warhol's lost installation as "a brilliant conceptual work but also very physical because we actually had the mechanical alarms. It was like a kinetic sculpture in some way: a sound sculpture, a light sculpture. But there was nothing there; it was totally invisible...."
Tom Friedman's conceptually-inflected practice is coupled with a wry humour well illustrated in his Untitled (A Curse) (1992, above).
Riffing, perhaps, on Warhol's similar-seeming Invisible Sculpture, and certainly approaching the notion of the dematerialised artwork with a sense of impish fun, Friedman's plinth is posited as not empty at all, but supporting a large ball of space that has been cursed by a witch.
Friedman's conception of a very real invisibility extends to travel arrangements for the piece: its transportation crates always include enough extra inches to accommodate the hexed air.
A similar-seeming pedestal (Untitled 1992, detail below) bears a literally scatological joke.
Although appearing empty, a tiny ball of the artist's faeces is centrally positioned on the cubic plinth. The sphere/cube combination not only revels in challenging humour, it invokes a precise approach to formal composition that can nevertheless hardly be seen.
Like Friedman, above, Maurizio Cattelan is concerned with the production of amusing yet revealing absurdities.
Untitled (Denunzia) (1991, below) consists of a police report earnestly filing the claim that an invisible sculpture had been stolen from Cattelan's car.
Purportedly conceived when the artist was struggling with ideas for an impending show, Denunzia neatly replaces absence of inspiration with an inspired parody of the absent artwork.
Yet it isn't just about poking fun at the credulity of non-artworld ingénus or, indeed, at conceptual art itself .
Rather, Cattelan's serio-comic meditation underlines the immense power of suggestion and its even greater persuasiveness within clearly defined contexts. Fundamental to the evocation of immaterial art, suggestion propels our leap of faith into the non-physical void.
1. This work is occasionally accused of making the Italian police force the butt of a rather supercilious joke, but it also suggests a surprising awareness of 'difficult' artistic precepts among the wider public. After all, 'Denunzia' closely resembles the entirely earnest strategies through which many other artists have formulated disembodied artworks, and the mere fact that Cattelan's claim was attended to at all points to an (actually rather laudable) awareness of key concepts in conceptual art.
It should also be noted that, in the report itself, the description of the missing artwork as "invisible" is surrounded, as here, with rather cautious quote marks.
Expectation arising from context is certainly a key factor in the reception of Matt Sheridan Smith's Self-portrait (Golden Sections), (2009, above).
At first glance, the array of empty plinths appears to echo the absences endemic to the works so far discussed; yet as the title of the piece clearly indicates, we're not seeing objectless platforms at all, but a representation of the artist himself.
Each plinth corresponds to a bodily measurement taken according to the Golden Ratio, the mathematical formula widely applied to classical art composition.
Although this also means that Sheridan Smith's piece can hardly be defined as invisible, it deftly plays with notions of absence while simultaneously exposing the deeply embedded conventions of display through which the other plinth-based works featured here operate. We're as unlikely to view the columns as a kind of three-dimensional bar chart as we are to instantly identify the work as a form of portraiture.
Conceptual art meets new media in the work of Italian artist Bolognini, whose networked computers are programmed to create "out-of-control infinities" of continually generated random images.
The Sealed Computers series, initiated in 1992, goes one step further by preventing anyone from seeing what the machines are creating: their monitor buses are sealed with wax, disabling any connection to a screen and thus rendering their endless production entirely invisible.
The absences underpinning Tino Sehgal's carefully choreographed "constructed situations" lie in their insistently ephemeral status.
They are not meant to be photographed, catalogued or physically illustrated, and produce no other artefacts. Sehgal's works, therefore, reside only in the space and time they occupy, and in the recollection of their reception.
The 2007, alternately titled This Success (or) This Failure, for example, featured young children in school uniforms attempting to play without using objects (photo of 'interpreters' above, is not of the performance itself).
With the declaration "I think this work is called 'This Success'" or "I think this work is called 'This Failure'" the children attempted to entice visitors into joining their games.
Sehgal's 2010 This Progress at the Guggenheim, New York, saw the museum's famed spiral gallery emptied of all art works (left).
Instead, visitors to the show were greeted at the ramp's base by a child who asked for their definition of progress, a conversation which was resumed, during the ascent, by a high school student, then various representatives of adult age groups ending with a white-haired interlocutor at the upper-most point of the gallery.
Sehgal's insistence on his art as a fleeting, non-documented interaction makes for particularly interesting circumstances regarding its purchase and resale, which is conducted through oral agreement before witnesses, and specifically excludes written instructions, a receipt, and use of a catalogue or pictures.
Used in a figurative sense, 'invisibility' has always referred to the overlooked, marginalised or unnoticed. In concrete terms, perceptions of reality can be vastly altered by what is withheld or omitted. And for a variety of reasons, we may actively choose to 'make ourselves invisible' (exemplified, perhaps, by Chris Burden's 1971 performance during which he disappeared for three days) or, equally, feel entirely unacknowledged.
The following artists utilise the unseen to pass astute comment on what we choose to pay attention to, or what is selectively made visible to us.
Although New York artist David Hammons' practice is eclectically diverse, several of his more enigmatic works beautifully demonstrate semi-visibility as a strategy of evasion or inaccessibility designed to reflect wider realities.
For a 1995 untitled show, Hammons added his own, unlabelled sculptures to a New York store's stock of African and Asian artefacts.
Many of his pieces (such as Tape Duck, 1994, above) actually incorporated the shop's wares, vastly complicating the experience of locating Hammons' work amongst the many items displayed.
More than simply an exercise in prankish concealment, however, the show deftly underlined several concerns through which Hammon has consistently defined his practice.
Quite literally instigating a blurring of identities which Hammons' work as an African-American artist has frequently referred to, it also addressed the tendency for marginal or minority presences to be misrepresented, lumped together or generally rendered only partially visible.
Such reflections on status quo lead, in turn, to a questioning of the pomposity of 'high' art and its often exclusionary milieu. (See also invisible art shows).
In recent works, Hammons has again embraced the issue of transitional or partial states of concealment by shrouding paintings in patched rags and plastic tarpaulins (left and below).
This apparently simple act of veiling raises disproportionately complex questions as to what exactly, we are being asked to see.
On one level, of course, the answer seems perfectly straightforward: Hammons' covering act simply limits access to the 'real' image beneath. On another, the inextricability of the tattered semi-coverings clearly points to works that consist of both elements.
Yet for one such piece, at least, the artist's specific instructions exist as a guide to its viewing.
The white cloth draped in front of Hammons' Untitled (Kool-Aid) (2003) - exhibited in 2012 at New York's MOMA - was only drawn aside following e-mail requests to return to the museum on another day, at an allotted time, in order to witness a white-gloved assistant reveal Hammons' now-you-see-it, now-you-don't artwork.
The work of New York-based Chilean artist Alfredo Jaar is generally political in nature, his subject matter often approached via detailed interrogation of the media through which it is documented and represented.
Africa, in particular, is of enduring interest to Jaar, not only with regard to to its complex political and cultural histories, but especially in terms of the way these appear to be mis- or under-represented in the West.
Searching For Africa, for example (1996, above), compiles 2126 issues of 'Life' magazine spanning several decades in order to demonstrate an almost total absence of cover stories devoted to the continent (the few which do exist engage principally with issues such as AIDS and African wildlife).
Even more startling is Jaar's (untitled) assembly of 17 covers from 'Newsweek', each corresponding to dates in 1994 during which the Rwanda disaster was unfolding (below).
Starting in April, all fail to highlight the increasingly devastating crisis until, on August 1st, a report on the massacres finally makes front page news.
A more recent work, May 1, 2011 (2011, below) focuses on White House reports of the assassination of Osama bin Laden.
A screen displays the widely disseminated official photograph of President Obama and his security team as they allegedly witness a video feed of the event. Next to it, an identical monitor shows only a white background, its blankness indicative of the unseen footage supposedly being observed.
A caption to the right of the White House image identifies all the political figures present, while a blank card next to the white screen records only a total lack of information.
Contrasting the officially visible with the questionable, unanswered and unknown, Jaar's work not only confirms a deep mistrust of pictorial representation, it underlines an absence that is already conspicuously present.