We are coming close to finishing a current addition/remodel to an old schoolhouse built in 1900 for some customers to become their vacation home and vacation rental. We have maintained as much of the original building and look as possible and we are putting in a small deck off the master bedroom that will be redwood. They don't want to stain the deck, but want it to look aged like it's "original". Any tips for getting that weathered grey look to a new deck? I've done some quick searching and have come across baking soda and water, but seem to see varied results and satisfaction with that. Have head muriatic acid mentioned. Any other products or techniques?