That's lovely Nick, as usualy. I got your mixing set for Christmas and I'm enjoying exploring them. Berber Blue is also a pleasant ink on its own for writing with.
What do you tend to use for black? Was it applied before or after the wash? I'm trying line and wash (with both your inks and watercolours) and I often get black bleeding. Even Platinum carbon black can bleed if it's not totally dry. I'd forgotten that Higgins Eternal isn't waterproof, to my cost. Kuretake sumi ink is waterproof, apparently, but the timeframe for it to actually dry enough to apply a wash over it is, apparently, about 100 years. I prefer fountain pen or dip ink for line quality - I find pigment liners a bit boring, although they are at least more consistently waterproof.
I haven't used any black. This is just using Randall and nothing but Randall. It's a commission for TV producer in the US. The rigging was done using a dip pen with a Zebra G nib. It may appear black but it is in fact Randall.
Glad to hear you have my 4 colours. I'm just about to start making ink art tutorial videos and will be covering just about everything I do. More info on my YouTube channel - have you subscribed?