Why are some pressure treated wood heavier than other?

Some pressure-treated wood is heavier than others due to the type and amount of preservatives used during the treatment process. Different wood species also have varying densities, and the pressure treatment can increase the wood's weight by infusing it with chemicals like copper, chromium, or arsenic compounds. Additionally, the treatment process can lead to different moisture content levels, further affecting the weight. Overall, these factors contribute to the variability in weight among pressure-treated wood products.