Using Blue Water

• Cut the stem of a rose at a 45 degree angle and place it in a vase of water to which you've added 10 to 15 drops of blue food coloring. Leave the rose there overnight. Using a white rose will allow the blue coloring to show up better, but any color of rose can be used. If a different color of rose is used, the blue coloring might not show up as well.
  
  

Significance

• The rose turns blue because the rose has a system similar to the human circulatory system, which pumps blood through the body. The rose has what is called a vascular system, which pulls up water from the base of the stem and circulates it throughout the rose. Because the water is colored with food coloring, the petals will turn blue as they fill up with the blue water.
  
  

Rose Petals and pH

• Rose petals contain a chemical called the oxonium salt of cyanin; when added to water with a high pH, between 7 and 14, this chemical will turn blue. Another liquid that has a high pH that will also make the rose petals turn blue is a mixture of one part ammonia and one part sodium hydroxide. Adding rose petals to a solution can help determine if the solution ranges between acidic and basic. Other red plants that turn blue in such bases include cherries, geranium petals and beets.
  
  

Dyeing

• Rose petals themselves can be dyed blue by either spraying them with dye or by placing a whole rose in blue-colored water overnight. Using spray-on dye can result in staining of clothing or fingers, while using the blue water method will result in petals whose color does not rub off.