1. Prepare one or two upside-down cookie sheets (air underneath the sheet will help the candy to cool faster), by covering them with parchment paper and spraying it with oil.
2. In your pan, over medium heat, stir together the sugar, corn syrup, water, and cream of tartar with a wooden spoon until the sugar crystals dissolve.
3. Continue to stir, using a pastry brush dampened with warm water to dissolve the sugar crystals clinging to the sides of the pot, then stop stirring as soon as the syrup starts to boil. To get to hard crack stage, it takes 15 to 20 minutes of hard boiling. Do not leave the pot unattended even for one second.
4. You are boiling the sugar to the hard crack stage at 300°F-310°F (146°C-154°C) where the sugar concentration is at 99% and the water is at 1%. This happens just seconds before the sugar begins to brown and caramelize. At these temperatures, there is almost no water left in the syrup.
5. To read the temperature of the sugar without a candy thermometer, drop a small amount of the syrup into cold water and it will form hard, brittle threads that break when bent. CAUTION: to avoid burns, allow the syrup to cool in the cold water for a few moments before attempting to touch it.
6. Remove the pan from the heat immediately and let the syrup cool to about 275°F (135°C), and the trick is that when you lift a spoon from the sugar mixture, it pours and leaves a thread on top of the surface of the melted sugar, and isn't extremely fluid like when you first took it off the heat. At this stage, stir in some gel food colouring.
7. Working quickly with a long spoon, drizzle the syrup onto the prepared papered and oil-sprayed sheets into the shape of fireworks as demonstrated in the image below. Allow to cool completely before handling. Top on cupcakes or a cake just before serving.
