Need advice on priming board

[Tito Champena]

Thank you for the explanation Karin, I understand now why Renoir painted the lights very thin because he was using the white of the canvas as his light, something completely opposite of Rembrandnt's technique that was in accordance to the classic principles that you describe. I think the painting on the hard board that I have is going to be all right without having to make it whiter. Only in this Forum one can ask an experience painter for advice before making costly mistakes. Thank you all for taking the time to answer my silly question.