Watercolor paper, not laying flat

[naturespeakstome]

Hello!  I just started painting, on watercolor paper, & noticed, it doesn't lay flat.  Is this common, & is it a concern, for when I want to sell my watercolor art?  I placed in a hard card sleeve, so it can flatten out, helped a bit, but not completely.  Wondering is this is just a common occurance, & should there be a concern, for when I auction, my paintings.  Any feedback is much appreciated!!

[jb5710]

what size watercolor paper do you use?  I always use 140 lb. Arches and have no problem.  90 lb. I find is too thin.  When I paint my ACEO's I usually take a commercial trading card that is the ACEO size and trace around it, then I cut about a quarter inch out from the trace and use masking tape to tape it down that keeps the paper flat.  Of course once the painting if down the tape is removed and I am able to cut the outside edges.  Hope that helps some.