Piping gel is used for water, teardrop and raindrops. I used this recipe to make the water in this picture:
1 tablesspoon unfloavoured gelatine
colour; I recommend edible airbrush colour
1 tablesspoon cold water
1 cup/ 2,4 dl glucose
Dissolve the colour in water. Add gelatine, and heat the sausepan under very low temperature until everything is dissolved. Add glucose and stirr thoroughly. The piping gel is now ready to use/ or keep it in an air tight container in the refrigerator for a couple of weeks.