Barry Herniman looks at the different ways to keep your watercolours moist when painting en plein air and extend their life.

When I first started painting with watercolour I encountered an ongoing problem: how to keep the paints moist. Once the pigments dried, they became as hard as rock and it was difficult to rejuvenate them, if at all!  

I used everything from a wet sponge in the palette to wrapping in clingfilm, but nothing seemed to work. If I left the sponge too long, mould formed on it. The clingfilm just became covered in pigment.

What I need was a paintbox with a compartment for my squeezed tube paints, which also included some deep mixing wells. All fell short in one way or another, and none had deep wells. I ended up purchasing a handmade paintbox... but it was quite pricey! 

Top tips for keeping your watercolour paints moist

• If your paints are in a pan ensure the lid is always closed 
• Keep your tubed paints in a cool, dry place and always ensure the lids are tightly closed 
• For tubed paints only use tiny amounts. The great thing about watercolour is that a little will go a long way 
• Keep a moist piece of kitchen roll/paper towel in your palette when you’re not using it. Give the paints a quick spray and then pop the kitchen roll on top. If you do get a bit of mould, simply scrape it off, it will not affect the overall colour or behaviour of the paint 
• Store your palette in a sealable plastic bag in a cool and dry place (maybe even in the fridge during the summer) 
• Go for quality paints as they will last longer than the cheaper variety. They will also have better pigments with more intense colours 
• Don’t be stingy with the amount of water you add – water is, after all, the main component of watercolour 
• Also, remember you can always rehydrate the paint that is left in your palette 
• Always take a spray water bottle – these can come in handy 

Looking for more painting holiday advice? Check out our collection of handy guides with top tips from artist tutors

And finally... 

• Set up your outside workspace in a shaded area, protected from the wind 
• If you can, paint outdoors in the morning or evening – avoid mid-day and the afternoon when the sun is at its strongest 

Take the next step: Visit our Ultimate Guide to Painting Holidays for essential resources, practical tips, and links to all the articles in this series.

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Barry Herniman runs painting holidays, demonstrations and workshops.