cleaning rough sawn timbers

I have rough sawn timbers that are weathered/grey. I have heard log home companies use oxalic acid in some form to bring back the initial natural tone of the wood. I'd rather not sand or plane them as we like the rough sawn texture. What are other experiences in keeping rough sawn timbers clean and "fresh" looking?

I only have experience of English Oak, but have found that oxalic acid while being great for removing blue iron stains, will not get rid of the greying.

Note well that Oxalic acid is VERY TOXIC
use gloves, and all other relevent H&S measures!!