Well, i have checked out the D.I Markers on the last 2 card/thick paper swatches. Even on 160gsm card/thick paper, the markers work lovely and even though water is added, the colouring doesnt even show through on the other side of such thin card, so i now know that i can use any of the cardstock i have with these pens!!
Below is the 240gsm card, i only have A5 pieces of this but its the idea you need
Below is the 160gsm card/thick paper, this is great to know as the people who have printers that won't take thick card will more than likely have 160gsm card/paper which will go through most printers
Hope i have helped people with questions of what paper or card these markers will watercolour with!
Thanks for looking guys, Hugs&Blessings, Vick xx