Purchasing Turner by the Brushstroke

If you’ve finished donating to Philadelphia’s Eakins campaign and are looking to save another artwork for its homeland, London’s Tate Gallery has just the thing: For a mere £5 you can buy a brushstroke of Turner’s “The Blue Rigi,” as part of the campaign to keep it from going to the private, non-British collector who offered £5.8 million for it at auction last June. The British government imposed a temporary export ban to allow a public institution to raise the £4.95 million (a lower amount than the auction price, because of tax benefits to be granted the seller).
The Tate has already kicked in an unprecedented £2 million and The Art Fund, an independent British charity spearheading the public campaign, added £500,000. They hope to raise at least £300,000 through the brushstroke gambit and other public donations, but the total donated so far is a mere £21,054. (To be fair, the public campaign was launched just two days ago.) The deadline for preventing the export is Mar. 20.
Why does a museum even richer in Turners than Philadelphia is in Eakinses need this watercolor, which would be its most expensive purchase? The Art Fund explains:
There’s no question that this country is already rich in its holding of works by Turner. But the great majority of watercolours in the Turner bequest are sketches and preliminary studies, vital for the study by artists and art historians but not in the same league as “The Blue Rigi.” The Rigi Watercolours exhibition [opened Jan. 22] will for the first time show the work alongside both its companions [“The Red Rigi” and “The Dark Rigi”] and the preparatory material: visit the exhibition and judge for yourself.
To lend a little celebrity caché to this campaign, artists David Hockney, Peter Blake, Michael Craig-Martin, Martin Creed, Jeremy Deller, Peter Doig, Antony Gormley, Howard Hodgkin, Anish Kapoor, Fiona Rae, Bridget Riley, Mark Wallinger and Rachel Whiteread all bought a brushstroke.
Gee, can some of these art stars spare more than a five-spot? And is a bank loan, like the one secured in Philadelphia, an option if the fund drive falls short?
And the most important question: How long can museums go on trying to mount emergency fundraising appeals to match the record prices set by money-no-object collectors?