I've been torn between the Derwent Graphik Line Painters and the Winsor and Newton Watercolour Markers, and after a coule of trips to Rennies Art Shop in Liverpool where they very helpfully let me try them both, I decided to go for the line painters on the grounds that the drawn lines were easier to wash away.
I chose 2 pens: Brilliant Blue and White.
I wanted to use the white pen against a dark background to give a striking and luminescent effect, so I began by painting card with dark blue, red and purple acrylic paint.
Once the acrylic background was dry, I opened my white pen. The ink is dispensed through a nib operated by depressing it slightly, and once it began to flow I found I could get a lovely fine line that washed out very nicely with my waterbrush. However after a very short time the flow stopped and I had to gently depress the nib again....at which point the pen started to blob and drip. Fortunately I'm used to working fairly loosely with my paints and am very fond of flicking paint around, so just worked the blobs into my painting.
I'm very much into sketching whilst I'm out and about, one of my favourite activities is drinking coffee and painting in my local coffee shop. Sadly this pen isn't going to be accompanying me on many of my painting adventures...the second painting took far too long to dry, over half an hour. This is too long for me to wait, and I ended up carrying it around the shops with me in my hand until it was dry enough to pack away.
With the blue pen I chose to paint an owl that I had seen the same day that I bought the pens. The blue lines did not wash away quite as well on my 300gsm "NOT surfaced" watercolour paper, and to make adequate washes I had to wet the paper first and then very gently drop ink in, then wash it away. Not ideal, but not insurmountable!
I decided to keep the white pen for adding highlights to my work as it really is very very white, but on the whole I cannot recommend these pens.