Most preferred: Ziller white ink: it is opaque, nice flow,
good hairlines but it needs gum arabic added because it erases
Pro-white was next, opaque, good flow, easy to work with,
the hairlines were OK, stays put with erasing.
Zinc white gouache was OK, smeared a little with erasing.
White pearlescent is waterproof, opaque, easy flow, but had
consistently thick hairlines.
Silver pearlescent didn't flow as well as white, can get hairlines.
FW Acrylic is waterproof, opaque, flows too fast.
Permanent White gouache was hard to work with and inconsistent
in its flow.