After wondering about the existence of white ink, I checked with my printmaking teacher and she pointed me to the Daniel Smith catalog. They carry a series of acrylic artist inks that are usable in technical pens. The white ink is permanent and opaque. the item number is 066 070 029. Cost is $4.69.

View it on line at

http://www.danielsmith.com/products~cat~350~sku~066+070+029.asp

David Damico
Houston, TX