Although John Walsom ROI ARSMA has not always been a plein air painter, he says "it's become the centre of my working life. It's a tricky business, and the results don't always match our expectations. They do usually have the immediate look of something done on-the-hoof (at least, mine do), but without repeat trips they can't have huge amounts of detail or re-working (mine again)."

"Lockdown forced a lot of us into different work practices, especially if we were used to going out to find our subjects. Making bigger pictures from my plein air studies was a way for me to keep happy working in the studio, and I'm doing it more, even now that (for the moment) I don't have to.

My most common plein air size is 12 x 16", I work on gessoed boards, with a mid tone pre-applied. Recently I've been carrying bigger canvases, usually 24 x 30", in pairs with spacers, but for marine subjects, the wind is very often a real problem with work of this size. My painting of Flushing in Cornwall, which is showing in this year's RSMA show, was almost completed on the spot, but I was standing at the edge of the quay, and a wind from my back got so strong that I was having real trouble stopping the canvas (with me attached) flying off over the water. It was my last day in Cornwall so I took a photo and finished it off in the studio.

Flushing, Cornwall Oil 61 x 76 (76 x 91 cm framed) £3,200 - Buy Now

My plein air painting of two historic oyster dredgers at Mylor, the Six Brothers and Boy Willie, was only 10 x 12". I wanted to work at sight-size, because the shapes of the boats from this angle can be really challenging if you can't easily do measuring with your brush. I needed to be quite close because of the road behind me, and couldn't fit both the hulls into the composition, so I cropped off a bit of the one on the left, which I thought looked ok. I just managed to include enough of the sky to suggest the cloudy sky in the distance. I was working hard on getting the shapes and tones right, and thought much less about atmosphere or mood.

It was accepted for the RSMA exhibition in 2017, and I thought it was strong enough to be worked up into a bigger painting, so in the studio I used a 24 x 36" canvas. I widened the view slightly, to include both hulls, some more sky, and the bottoms of the prows, so the boats are more visibly sitting in the water. I think the extra sky and water has allowed me to show the atmosphere of the day better, so it's more than a factual record of what was there. Although there's more detail in the marina boats in the background, most of it is just made-up patterns of boaty shapes and shadow. This painting was shown at the RSMA show in 2018.

Boats at Mylor Harbour Oil 76 x 91 cm

On a rainy Sunday in 2017 I did a little 10 x 12" painting of Hammersmith Bridge at low tide. There were some nice bits of bright red on the barges sitting in the mud, and I liked the contrast with the dull green of the bridge.

Searching for lockdown projects in April this year, I dug this one out, and thought I could make a bigger version. I had a 20 x 24" board, and because the proportions were the same as the original, I did a basic squaring-up (just into quarters) to copy the shapes at double the size, as I quite liked the composition as it was. It's difficult to keep the immediacy of a hurried sketch in the rain, when you've got all the time in the world and a cup of tea on the side, but with the help of bigger brushes and a self-imposed ban on Radio 4, I got a result that, I think, keeps the feeling of a grey London day. A strict no-fiddling, alla prima only rule also helps at times like these.

I was going to Cornwall most years, long before I started to paint there. Last September, on a return trip to Mylor, on the South coast near Falmouth, I was at the marina, very close to the location of the Seven Brothers and Boy Willie painting above, but at low tide, while I waited for my kids and their friends to come back from kayaking around the creeks. I clambered around in the mud for a while, and got very interested in the sun reflecting from the coloured lines between the oyster dredgers and the shore. It was helped by a strong contre-jour light, with the sun above the right hand corner of the view (always carry a peaked/wide brimmed hat). I really wanted to get it finished before they got back and demanded lunch, and that urgency helped me to keep it fresh, I think. A yacht was out of the water being cleaned on the harbour-side, and I could see some activity between the masts and rigging of the fishing boats. The profiles of the hulls were very elegant, especially the way the black one was just gently touching the ground, with sunlight shining underneath. Amost the best bit for me though, was the surface of the mud, and the sun glinting on the bits of shell and rock.

It was only a couple of months later that I decided I had to make this into a bigger painting. The canvas I used is 70 x 100cm (about 28 x 39"), so a bit wider in shape than the original. I didn't want to lose any of the top or bottom, so just extended both sides, to see a bit more of the stone bank on the right, and the boats and blue tarpaulin on the left. Both of these help, I think, to locate the view and make it clear what's going on. Otherwise the composition is pretty much identical. I always work on a toned surface, and covered the canvas in something like the same colour which shows through in places on the original board - a purply mix of ultramarine and cadmium red. I made a bit more of the reflections in the mud, and highlights on some of the lines and bright edges, to bring out the contre-jour feel.

Mylor Yacht Harbour, Low Tide Oil 69 x 99 (84 x 114 cm framed) £3,400 Winner of The Baltic Exchange Award 2020 - Buy Now

I knew there had to be a reason why I kept hundreds of old plein air studies, often of dubious quality. It's good to know that, if the world keeps me stuck inside for a while, I've got plenty of material to work on, without having to get the photo album out."

John Walsom's Mylor Yacht Harbour, Low Tide was awarded The Baltic Exchange Award on 30 September 2020.

It can be viewed, along with the rest of the Prize Winners, as part of the Royal Society of Marine Artists Annual Exhibition in the gallery until 10 October. 

Book your ticket to visit the Exhibition