Here is a new entry.
No watercolors without water and the classical jam jar !
This scene has been rendered with 64000 samples per pixel, in around 10 hours. Rendering with Pathtracing was necessary because of half-transparent materials. As the transparency effects with Directlighting didn't allow to setup the materials, the whole setup has been done with Pathtracing enabled.
It was really difficult to setup because the glass area has been very noisy for a long time and it was not easy at all to see the effects of the settings. Getting details in the jam area required much light, and so I fear that the other parts of the scene are a bit over lit. Despite the very long rendering, many remaining hot pixels have been removed.
The main things that I wanted to achieve were the water wave and the dilution effect of the paint, at the tip of the brush. I hope that it is believable enough.
As there are three transparent materials and four transparent surfaces (glass, water and diluted paint) and because the water and the diluted paint effect are behind transparent surfaces, it was difficult to select them. So I have added invisible objects under the table using the same materials. It allows to select the materials without using the scroll cursor of the GUI, which is not responsive enough on my machine.
@Diogo : to get rid of the black bottom, I have increased the light and set the alpha of the glass around 50%. I encountered the same effect with Indigo, with glass materials very close to the table surface. I don't know if it is the same problem here, though. I have not yet experimented with the specular ray depth... it can be a clue also, as there are several transparent surfaces.
You are right ! Hell, how di I missed that ? My watercolours box measures 6 meters ! 
