How do you make pressure treated lumber?

Answer 1

http://en.wikipedia.org/wiki/Pressure_treated_lumber

Answer 2

Hi. I always thought they subjected to wood to a vacuum and covered it with the preserving chemical, which enter deeply into the wood when atmospheric pressure was re-introduced. But it could be positive pressure as well.
From the site provided by the first answer : "LOSP treatments often use a vacuum impregnation process. This is possible because of the lower viscosity of the white-spirit carrier used."
So I guess both pressure and vacuum methods can be used.

Answer 3

By applying a wood preservative under pressure so that it impregnate all the pores of the wood.