I recently bought an old house. The post and beams was claimed to be from a 1718 tavern, reconstructed into a great room. It looks dark and old. I tried cleaning a portion to see what the natural color of the wood is. I use water and detergent and started scrubbing with a brush. The wood is covered with thick black dirt. I let it dry and the wood now looks light (my friend said it's an oak wood). I am worried that I damaged the wood by scrubbing with water and detergent and probably stripped off the natural color. It looks raw wood unfinished. Can someone please tell me how to clean this effectively? It's impossible to do this manually, scrubbing by hand. We are thinking of using sandblasting. Would that damage the post and beams? I appreciate any advice.