In a heavy-bottom, high-sided saucepan over low to medium-low heat, combine 1 cup sugar, water, and a drop of lemon juice (the lemon juice keeps the mixture from hardening). NOTE: I find that by maintaining a low heat on my stove, I have more control over the caramelizing process, as it is really easy to burn.
Cook, stirring constantly with a wooden spoon or silicone spatula, until sugar dissolves and mixture just begins to simmer. Sugar melts at about 320 degrees F. and will turn to a clear liquid at that temperature.
After sugar dissolves and syrup is simmering, cook for approximately 8 to 10 minutes, without stirring. Hold handle of pan and gently tilt the pan off the heat to distribute color evenly as sugar caramelizes. NOTE: Boiling times will vary according to different stove tops and other factors.
If using a digital instant-read thermometer, the temperature on your cooking thermometer should register a final temperature of approximately 340 to 350 degrees F. and the syrup should have a golden brown (light amber) color. Watch the changing of the color and the temperature carefully as it can go past the light brown stage quickly and burn. If you think it is close to being done but are scared of burning it, you can take it off the heat and it will finish due to the residual heat.
Immediately remove from heat and pour into individual ramekins or custard dishes, coating the bottoms evenly (tilt the dishes so that the caramel coats the bottom).
Set aside and let cool. To stop the caramel from cooking, some recipes have you dip the bottom if the pot in ice water for 10 seconds.
Photos showing stages of the caramelizing process:
Stage 5 - Done - Remove from heat immediately.
Once the caramelizing process is complete, and if you will be making a caramel sauce and will be adding cream or another liquid, this should be done very carefully, as the liquid will hiss and sputter. Add the liquid at the edge of the pan, slowly, and stirring as it is added.
Water boils at lower temperatures at higher altitudes. At sea level, the boiling point of liquids is 212 degrees F., but for every 500 feet above sea level, the boiling point decreases by 1 degree F. due to less resistance on surface molecules. For example, at 5,000 feet, water boils at 202 degrees F., which is 10 degrees less than at sea level. The lower the boiling point, the quicker evaporation occurs.
High altitude: For every 1,000 feet (300 metres) that you are above sea level, subtract 2 degrees F. (1 degree C) from the temperatures given in your candy recipe.
Caramelizing Sugar Recipe - How To Caramelize Sugar: https://whatscookingamerica.net/Sauces_Condiments/CarmelizingSugar.htm