Dr. Ph. Martin's Pen-White is an highly opaque ink and is ready for immediately use straight from the dropper. Shake well before use and clean your nib with water after use. You may also mix it with other ink/gouache to create a pastel color.
 
This non-waterproof white ink is highly recommended by Alice. It is a very good alternative to Bleed Proof White if you are a beginner and not familiar with mixing ink.