Back to the previous points, timing is pretty critical with any acid staining job, but so much more when a driveway ideas project is as large as this one was. Acid staining is a reactive process and it will continue to react the longer it remains wet while lying on the concrete surface, creating a darker color. Ok, so how does this affect anything?
Simple, if you have a long, tree-lined driveway and the part of it is in the shade and the other in direct sunlight, well, there can be a lot of color variations throughout; and keep in mind that the shadows will move during the application, further complicating things.