How the timbers are treated?

They are loaded onto carts and closed in a large vessel where liquid with the active chemicals is pumped in at high pressure to force the liquid into the wood. There are two different ways it is done. The way that is used for building materials starts with kiln dried wood and land scape timbers are generally done wet. What this does is not allow as much treatment into the landscape timbers and they will rot sooner. You may see "treated to refusal" on the landscape timbers. This means they pressurized the vessel, but due to the water already in the wood the treatment did not reach the core.