I lived in the UK for many years and whilst I was there I never really had a problem with drying time. Since I'm back in Sicily though, things have changed. It's not so much of a problem in winter, but in summer it's so hot the paint almost dries in my brush!
So if you have the same problem, here are a few tips for you:
Arisarum vulgare on Arches Hot Pressed Paper
You can add Ox gall to your painting water. Ox gall is a wetting agent usually added to paint to help pigments to disperse more easily. Added to the painting water increases the flow and blending capabilities of watercolour and extends drying time.
Choose a hard-sized watercolour paper. This will be less absorbent compared to other papers and the paint will sit on the surface for longer before being absorbed.
You can also try using thicker paper.
Use Gum Arabic. This is the binder used in watercolors. If you add some Gum Arabic to the paint you will increase transparency and extend the drying time. One thing to keep in mind though, is that this medium will make the paint easier to lift.
Use watercolor blending medium which extends the time you have to rework the paint before it dries completely
If you don't have blending medium, try adding a few drops of honey to your painting water, but be careful not to add too much. Experiments with little at the time
Instead of honey you can also use glycerine
Try wetting the area to be painted twice; if the paper is already damp, when you wet it again it will last a bit longer before it dries
I hope you've found these tips useful and if you want you can also download my “Guide to Watercolor Basics and How to Choose Your Favourite Colors”where you will find even more information about watercolor.
If you have a specific question, please don't hesitate to leave a comment below or contact me :-)
Happy painting!