I had left the outside to weather given my reluctance to do the work and the weather being off. I also wanted to see what just a coat of Stockholm tar would look like after a while. Well the front face, facing the wind, became quite grey.

Here are two close ups of the weathered parts. The lower areas are more grey and it may be the scabbing is the residue from the Stocholm tar once the volatiles have evaporated. You can see quite a difference between the lower areas which have been coated more and take some of the run off from above. You can see the 'wood' in the upper picture so the grey may not be the wood being degraded by the sunlight but just the residue.