The Royal Watercolour Society was founded in 1804 by artists who felt slighted by the Royal Academy. John Varley, a founder member, is known for his elegiac landscapes that followed sketching tours in Wales.

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They were not records of actual places. Nature was there to be 'cooked' in the picturesque manner. Wales must glow like Italy. The Claude glass, a small darkened convex mirror, was the Photoshop filter of its day. It 'antiqued' the scenery. Varley was a capable astrologer, pressing you for your star sign. Visiting his ailing friend John Sell Cotman in Norwich, when the doctor had given him days to live, Varley exclaimed, 'Pooh! Nonsense!' He predicted he had another 20 years. In fact, there were 17. Cotman is buried close to Lord's cricket ground.

It was in Varley's house that William Blake drew his portrait of a flea – a portrait from his mind's eye. A small group, the Ancients, gathered around the elderly sage. Among them was John Linnell. In 1824 he brought along the young Samuel Palmer. (Linnell was to be his father-in-law). Palmer was later to remark: 'It pleased God to send Mr Linnell as a good angel from heaven to pluck me from the pit of modern art'.

I have recently become the honorary curator of the Society. Here I am offering a few footnotes to what can be seen on the web. Thumbnails have a purpose, but they don't give you the smell of the originals, the stories, the characters, the intrigues. Some of today's practitioners have roots that go back into this history, but it is a hidden history. Watercolours have to be protected from light, shut in boxes for much of the time. Tate Britain rotates a selection of its Turners and William Blakes, but many watercolours remain out of sight. In 2020 the RWS collection, along with its archives, will be housed in new premises in Whitcomb Street, next to The National Gallery, close to where the Society began.

I opened a box of David Cox landscapes, and gasped at the freshness, the sparkling light – I could almost feel the breeze. Informal sketches are in line with the taste of our day, but in 1853, Cox, at almost 70 years of age, expressed dismay that his 'roughness' was misunderstood. For more than 200 years RWS members have been debating how closely aligned they should be with contemporary art. Palmer was no realist. What appalled him was the materialism of modern life – farmland carved up by the railways, cities choked with smog. Cox – he had taken lessons with Varley – seemed happier, sketching the weather and the day-to-day goings on of his favourite Welsh village.

Watercolour has not always been Panama hats and cucumber sandwiches. From the start, rival societies sprang up, with splits and furious resignations. To this day you cannot be a member of both the Royal Watercolour Society and the Royal Institute of Painters in Water Colours. The longest-serving RWS president, Sir John Gilbert, well-known as a prolific illustrator for the Illustrated London News, became a painter of figures in the manner of Rubens.

His watercolours were worked up and finished to look like oils. He called the high detail of the Pre-Raphaelites 'vile'. Gilbert's reputation has slipped away, along with late Victorian 'exhibition watercolours' – sentimental cottages and costume dramas. However, there could be a revival of sorts, given the 'Poldark effect'. His earnest heroes and heroines pop up in web searches. Gilbert was keen on the Royalists of the Civil War, who stood for a lost spiritual age of chivalry.

The impressionists supplied the fresh air to kill off all that stuffiness. The loose handling of Arthur Melville now looks entirely 'modern'. John Singer Sargent's Bed of a Glacier Torrent of 1904 (shown in 2017 at Dulwich) is one of the treasures of the RWS.

The apparent ease, the flickering light, in turn, prompted a reaction. The critic Frank Rutter called it 'blob and swash'. In 1923 he advocated a return to the restraint of the early topographical draughtsmen – the 'tinted drawing' manner that the founders of the RWS wanted to leave behind. But Cotman's reputation rose: the muted tones, the flattened planes, resonated with Cubism.

Samuel Prout was famed for his architectural studies. In his Hints on Light and Shadow of 1838 he recommends moonlight as the ideal condition for drawing.

This belief in the primacy of drawing, with a puritanical suspicion of colour, kept resurfacing. Drawing manuals, including Ruskin's Elements of Drawing, warn against allowing children to play with the box of colours before they have done their drawing exercises.

Occasionally exhibitions based on collections spring surprises. At the 2017 Cotman exhibition at Leeds Art Gallery, I saw his studies of Dutch seventeenth-century pikemen – all in unexpectedly loud colour. Cotman produced these for his students to copy, as was the practice of watercolourists at the time, often despairing of their role as drawing masters, sometimes in military academies. Their fortunes, both financial and artistic were precarious.

Leafing through a leisure-painting magazine today you might think that watercolour had no history. It was just about washes and using the right paper, as if there was a single trusted and 'traditional' method. If the past is any guide the future depends more on dissenting voices, on wayward individualists like the wonderful David Jones.

Some of the artists we most admire today were neglected for decades – Blake was not 'discovered' till late in the nineteenth century, and Palmer in the 1920s, inspiring the neo-romantics, Graham Sutherland and John Piper. (Strapped for cash, the RWS sold some Palmers to pay for refurbishing their gallery in the 1920s, and a Cotman in the 1940s.)

Today there are traces of the past in the current membership: a topographical tendency with Liz Butler's jewel-like portraits of allotments, and Neil Pittaway's expedition records.

For painterly vitality and atmosphere, I would pick Julie Held's In the Night III, the dense purple evoking the world of Emil Nolde, with the candles as symbols of life and loss.