The oil resident left over is from the straps. You typically don't see it in lumber because it soaks in and dries and it sometimes stains in non-pressure treated applications. Composite boards don't allow for this. That is what I suspect it is. I love the white pillars, it provides contrast and blends with the white of the pool. Would it not have been possible to make a jig to help with the cuts? Although I assume it wouldn't be 100% accurate all around the pool either. But amazing job!
How hot are those boards getting with the sun? Splendid job man, splendid.
How hot are those boards getting with the sun? Splendid job man, splendid.