Winsor & Newton Drawing Inks are made from dyes and are very bright and transparent, but most of them fade over time. They are not lightfast (the lightfastness of a colour is how permanent it is or how unaffected by light it is). There are two exceptions, however: Liquid Indian Ink and Black Indian Drawing Ink. Although they are not officially classified as lightfast, they are archival, which means they are permanent.
Liquid Indian Ink is the more traditional ink produced from Chinese ink sticks. It is not waterproof. Black Indian Ink is based on shellac and is water resistant, which means you can apply paint washes over it.
By comparison, most of our Professional Watercolours are classed as permanent – but they do not give the same type of brightness. Winsor & Newton Calligraphy Inks are pigmented, so they also offer greater permanence.
Artists usually choose Drawing Inks rated T for transparency on the colour chart, to achieve high levels of brilliance and transparency.