During the extrusion process the recycled PVC granuals are heated up to 195 degrees the molten PVC is then feed into the tool to form the profile for the gravel board or post. Once out of the tool the gravel board is then immersed in water to cool the PVC down the water tank is 6mtrs long .
As you can imagine once heated to 195 degrees and even after been immersed in cold water the profile still retains some residual heat. When the gravel boards or posts are packed the residual heat can cause the boards or posts to sweat or breath and this can cause a blotchy pattern as shown in the photograph below. This is perfectly normal and after a few weeks in the sun and fresh air they will weather in naturally.