Once the sugar has dissolved, add the citric acid and stir. Prepare the syrup to a temperature of 107-108 degrees (can be measured with a cooking thermometer). If you don’t measure the temperature with anything, you can focus on the color. The syrup should be light, almost caramel color. To check the syrup for readiness, drop a drop of syrup on a plate, cool very quickly and grab a drop between 2 fingers, while their separation should turn out to be a “thick thread”. This indicates the readiness of the syrup.
Cool the finished syrup and put the container in the refrigerator. It can be stored for a long time, 2-3 months.