Whilst on the face of it, this looks a little like an ordinary selective colour treatment, it wasn't quite that simple. In this case I was trying to get the juice itself to gradually get stronger in colour as it left the carton, till it was full on orange in the glass.

The trick here was to layer two copies of the same image; one a full colour shot, with the second being desaturated (in this case by 75%). To the second layer, I added a foreground/background gradient mask, which had the effect of giving me a full colour image, but which gradually desaturated towards the top of the image. Next I added another layer and used the Channel Mixer to convert to B&W, using the built in blue filter. Finally, I used the eraser tool and my Bamboo tablet to gradually rub out the stream of orange and the contents of the glass, revealing the colour beneath. Nearly successful I think, but I reckon that perhaps the de-saturated layer might have worked better as a pure B&W conversion and then stop the gradient before it reached the nozzle in the carton. I need more practice with a tablet too - just be grateful you can't see the original 3456x2304 PSD file.

This was taken for Week 5 of The Photo Forum's Boxer Turtle competition