Liquid Pencil is available in six shades: GREY 3, GREY 9, YELLOW, BLUE, RED, SEPIA. I bought the Sepia which I feel has a more classic conventional look. They are available in 50ml bottles or 12ml tubes. I've read online reviews saying that these can dry out in bottles but mine has been fine for months. Of course, to prevent drying out, one has to cap it air-tight.
And it seems like there are two versions, one that's rewettable and the other permanent.
Below are some swatches from Liquid Pencil and ArtGraf Watercolour Graphite.
To get a dark shade, Liquid Pencil almost has to be applied like a thick paste.
You can mix it with water to create different shades. If you don't mix thoroughly, you can get patchy washes. Compared to watercolour, it much easier to create patchy washes with Liquid Pencil. If you're someone who prefers flat washes, this product might not be suitable for you.
This is ArtGraf Watercolour Graphite. Textures for the two brands are quite similar. I've used coldpress paper with fine grain for these swatches.
Here's a sketch coloured with Liquid Pencil. Click for a larger view. The overall look is patchy, as mentioned before. If you apply in thick concentration, it's going to cover lineart. And there's no graphite sheen.
When it's dry, it's water resistant but not totally waterproof. So it will smear if you add another layer of water over. When I rubbed my fingers on the surface, I was able to pick up some graphite as well. So if you want to use this in a sketchbook, it's going to smear the opposite page. To protect the art, it's best to use fixative. I've tried erasing it also and it's quite resistant to erasing.
It's fun to use but I consider this a rather niche product. The main characteristic is the patchy textural look. Pencil offers more control that's for sure. But with Liquid Pencil, you can cover large areas quickly and it's good for quick sketches.