Description Diamine Registrar's Blue Black fountain pen ink is a deep blue-black that leans towards black and comes in a 30ml glass bottle. This is an archival and water resistant permanent ink for document signing. Diamine fountain pen ink is considered to be well behaved and smooth flowing, and has been made in the UK for over 150 years. Having trouble deciding between colors? Use our Ink Comparison Tool to quickly and easily view different colors side by side. We offer Free Shipping on all orders over $59 for US customers, and for orders over $250 for our Canadian customers.