Why timber colours differ when first delivered

We regularly get asked about why wood varies in colour. This picture shows Redwood posts which have been treated to the Highways Agency UC4 specification. On the same load are Spruce Rails treated to UC3 Highways Agency specification. The fact is that, as well as different species being used, no two bits of timber from the same species are the same so they react to the treatment solution in slightly different ways. Once on site however the colours will even out as the timber weathers and the end result will be spot on! Incidentally, all of this timber is heading to the same job in Yorkshire