Lee ... this humidity test was just shooting it on the range on a very humid day. I had to stop because it started raining, that is how humid it was. What I was looking for was clumping and misfires. You might be very well right that leaving a can open for a long time in humid weather would affect it. All I am saying by this simple test I did is, I had no problems today. It does get very humid in Northern Wisconsin, especially on a rain day.

Actually can you remember when it was called Clean Shot? I bought four or five pounds of it on a clearance sale. And I was shooting it out of a side lock. It was 2f powder of course. That was some of the best roundball powder I ever shot. I used to sit on the range and shoot all day.

One of them cans was open for over four years and it never went bad on me. But I do store my powder in a room off from the wood stove, so in the winter the humidity in my house is normally 16%.