I have recently been asked What inks are you using, when you write in white or light blue? This needs to be a quite opaque ink, right?
So here’s my answer: Thanks for your question! If I want to write in white, I use Dr. Martin’s Bleedproof White, you can order it for example from Blots Pen & Ink Supplies (UK) or from John Neal Bookseller (USA). I tried a variety of white inks, and this is in my experience the best for writing with pointed pen and regarding opaqueness. (It is also recommended by professional calligraphers of international standing, I learned about it at a workshop with the amazing Barbara Calzolari.) You have to dilute it though to write properly with it!
It goes like this: you add some drops of distilled water, then stir gently with a toothpick only the surface of the ink with the water, until you get some ink with the consistency of cream. For easier use I take out this liquid with a plastic pipette and fill it in a smaller container like a Dinky Dip. Now you can dip your nib and start writing! As you see, this ink makes very fine hairlines and very clean, precise writing possible.
For other light colors I like to use Ziller’s inks, they come in 10 colors which are mixable. The process is basically the same as with the Bleedproof White – these inks also need to be diluted (but not so heavily), so that they don’t blot or drop, or produce too thick lines. They are also waterproof once dry! Nearly all colored scripts you see in my blog are written with Ziller’s inks.
Of course you can also use Artist’s or Calligraphy Gouache – I just don’t have so much experience with those.
So have fun – writing in white is beautiful!