In a medium saucepan, combine 4 cups of filtered water with 1 cup of sugar
Heat the mixture over medium heat, stirring occasionally until it reaches a gentle boil
Continue boiling until sugar completely dissolves (about 2-3 minutes)
Remove from heat and let cool to exactly 110°F using your candy thermometer
While mixture cools, sterilize your glass jar by washing with hot, soapy water and rinsing thoroughly
Once the sugar solution reaches 110°F, sprinkle the yeast into your sterilized jar
Carefully pour in the cooled sugar solution
Leave the jar open in a warm, dark place (70-80°F) for exactly 24 hours
After 24 hours, attach your stopcock or balloon (if using a balloon, poke 2-3 tiny holes with a sterilized pin)
Let this mixture ferment for 2 full weeks in a dark place at room temperature