Guess what this is, before you continue to read!
I've written before about my fascination with old barns and I love the brown and grey color they get. When we built our smaller cottage for the teenagers (they were younger when we started) and guests that are visiting us, we built it with timber. That project took some years so the timber became natural grey and we have only painted the wind panels and window frames blue. On the porch we also have some furnitures that have transformed to grey because we have been too lazy, but I think they could need some kind of protection to live longer.
Three years ago we built a new outhouse as we don't have the facilities as water closet.... But we wanted that it should blend in the other buildings even if it had panel and not timber. So we decided to use copperas (iron sulfate) which is a way to get the wood look older. We had planed to paint it the first summer but things came between..... So the wood have started to became grey by itself.
But this summer we finally became chemists and mixed the products and finally painted the walls. Times will make the wood grayer but If you look carefully you can see a little difference already.
The chemistry mix on the first photo:
white- iron sulfate
blue - copper sulfate
brown - silver stain