My sketching’s mostly fuelled by Lexington grey, a wonderful ink made by Noodlers in the USA. I use it in almost every sketch I do as it’s rapidly waterproof, but also safe for fountain pens. It works well with water-colour washes, and you can use it diluted to quickly build very stable layers of tone and shade. I carry 3 water brushes loaded with the ink in different dilutions in my sketching kit. It’s a slightly smokey grey, warmish but neutral enough to work alongside all colours.
It’s always been hard to buy in Europe, so many thanks to the Sketching Forum for news of a UK supplier (last time I looked they had 27 bottles left… now down to 8 as of 10/1/14). I’ve stocked up with a couple of bottles and drew them, in Lexington grey ink, alongside my original big bottle from the US.
Fountain pen and water-brush with Lexington grey, watercolour, A6 – 20 minutes
Here’s a couple more similar Lexington sketches; boots and a teapot.
Fountain pen and water-brush with Lexington grey, watercolour, A6 – 15 minutes each
Mostly drawing 