When making candy or fudge a candy thermometer will make things much easier. They are cheap and available at most stores. You can always test your thermometer by placing in water right as it reaches the boiling point, 212 degrees F. If it is off you can adjust for that amount when cooking.Be sure and never submerge your thermometer in water to clean, gently wipe with warm soapy rag.
If you don't have a thermometer, don't let it stop you from trying a recipe, watch the time indicated in the recipe and be sure and follow it exactly.
For many recipes the Cold Water Test will also work.
When testing, remove pan from heat and place a few drops of mixture in to cold, not icy water, check chart below. Use a clean spoon and water each time.
Stage Cold Water Test
Thread (230-234) degrees candy syrup dropped from a spoon spins a 2 in thread
Soft Ball (234-240) can be shaped into a ball that flattens when removed from water
Firm Ball (244-248) can be shaped into a firm ball that does not loose shape
Hard Ball (250-266 ) forms a hard but pliable ball
Soft Crack(270-290) separates into threads that are not hard or brittle
Hard Crack (300-310) separates into brittle threads