I thought folks who like to draw their own designs and then have the lines disappear would like to hear what Helen has to say about Pilot's Frixion erasable pens. Heat erases the lines and cold brings them back. Helen mostly does Japanese Embroidery so she is using her pen on fabrics, not needlepoint canvas, so I cannot say whether they work well or not for needlepointers.
http://hgotts.blogspot.com/2017/01/more-gatsby-tools.html
On the other hand, they seem to be readily available, come in many colors (even metallics), so the mad scientists among us might want to experiment. Just let us know what you think, ok?
https://www.walmart.com/ip/Pilot-FriXion-Clicker-Erasable-Gel-Pens-7-Pack/22477879#about-item
Written by Jane/Chilly Hollow
Blogging at http://chillyhollownp.blogspot.com
and at http://chstitchguides.blogspot.com
© Copyright January 8, 2017 Jane M. Wood. All rights reserved.
