For many years I chose to paint my watercolour paintings in the traditional manner. I would only use watercolour paints on watercolour paper, which I enjoyed fully. If you have ever worked with watercolour paints you know how easy it can be to dislodge the previous layers of paint when adding new layers. This can cause smudging and muddying of your colours. So I was always very careful to avoid the need for a decorative outline around my images for this reason. Or if I wanted the clean graphic style of outlining I would take great care and a tiny brush or use black archival quality pens and markers to do the job.
Then one day while shopping at an art supply store I discovered something new to me, jars of super pigmented acrylic inks. They come in a good variety of juicy colours and can be mixed together for even more choices. Their liquidy fluid consistency is also very appealing and easy to use with a paint brush.
The beauty of using these acrylic inks is that once they are dry they are permanent and stable on your paper. You can wet your watercolour paper repeatedly and paint washes of watercolour over the dried acrylic inks and they stay put, no bleeding or lifting. Yahoo! This makes them perfect for those effects when you want to add a crisp clean outline on your drawing. The acrylic inks can be used first on dry paper before adding your watercolour painting overtop. Having lots of choices of colours makes outlining even more fun. Your creativity can really take off knowing you can use greens, reds, blues in ink outlines around your image.
In the photos above you can see that I used a teal green/blue colour of the acrylic ink to outline all around my decorative flowers first. Then once the ink was completely dry I was free to add layers of watercolour up against or even over the ink without fear of smearing or damaging my outline. Such freedom!