First of all, all the papers I usually have on hand were terrible, such as: Strathmore Drawing paper 400 & 300 series, Strathmore Charcoal paper, Canson Biggie Art papers, and several others. With most of these papers, very little paint would stay on the paper - I would just begin to rinse off the size and the colours would start fading. I tried to do less or more gentle rinsing on a few sheets, which preserved the colours better, but the paints are still rubbing off after the sheets have dried. Frustrating. Not good.
But I did find a few papers that work wonderfully.
1. Japanese calligraphy paper from Yasutomo & co.
2. Hilroy Studio Sketch Book, "for pencil and colour markers"
3. Color & Co Art Paper for Kids, "Drawing & Painting" 60lb paper
4. White Kraft paper rolls
5. Canson MiTeintes - I got mixed results with these papers, sometimes they worked and sometimes they didn't
I asked around trying to find out why so many papers are unsuitable for marbling. It seems that most paper is treated to such a great extent to make it acid free, then buffered and polished and shined and whitened or whatever... the paper just becomes unsuitable. Really, I don't know enough about paper making or the processes used by these various companies to know any specific reasons. I just know which papers worked for me. In the list of good papers, numbers 1 & 3 were also the best papers for Suminagashi marbling.
Now that I know what papers to use and I have been able to do quite a lot of marbling lately, I've actually decided to open up a second Etsy shop to sell some of it, MyMarbledPapers.Etsy.com.