I had a bad experience with this watercolor paper, and I do not recommend it.
A few years ago I bought a package of it. The first few paintings were a pleasure. After that the trouble started. The paper developed what might be described as translucent spots. These spots took paint very poorly and rendered the paper useless. Not every sheet had a spot, but out of frustration I put the package aside for a while thinking I had mishandled it. A while later, I tried again, and found that it seemed worse, with larger and more numerous spots. So I wrote them an e-mail explaining what I was up against. I asked what might have caused the problem, and asked if I did anything to create the problem. They did not answer.
After a few months, I tried the paper again and found that the spots now covered most of the paper, and that the paper was clearly deteriorating over time. I am so glad that I did not use much of it because of what those paintings must have looked like a few years down the road.
A new letter to St. Cuthberts Mill, the manufacturers of Saunders Waterford Watercolor
Paper, detailing the problem I had and asking what it was and what they do about this problem was again ignored.
My conclusion is to stay far away from Saunders Waterford Watercolor