Blue sky

The waterproofing liner used in biological pools is gray. Looking at a piece of this material in light gray, one wouldn’t easily imagine the transformation of the water’s color that will occur when the biological pool is full.

What is surprising is the blue of the water’s surface. Depending on the angle of observation, lower or higher in relation to the water’s surface, the tone of the color is darker or lighter, but it’s always a beautiful blue.

What transforms the gray of the liner into the blue of the water’s surface is the blue sky in Portugal. Although it’s the country with the most sunshine hours in Europe, there are as well some gray days. And whoever looks at the biological pool on those days will see a much more muted blue than on a clear day.

In short words, the color of the water in a biological pool depends not only on the color of the liner, but also on the color of the sky and the angle of observation.