Marcio, art 300 is tricky to work with. When developing, stopping, fixing and washing, it floats. I use an archive washer and need to peg the corners with tongs to keep it submerged. Also, the emulsion is very sensitive and after some time in water can peel off at the slightest touch. You have to handle it with extreme care.
I love using warm tone developer, sepia and selenium on it. I would not use it as an everyday paper, I prefer MG RC WT or Fiber for that. When I get an image and I think now that would look great on Art 300...