After many years of making candy, I have learned a few things. I don't claim to be an expert. But I have come up with a few tips that work for me.
Candy Making Tips
Always check your candy thermometer in boiling water to see what the boiling temperature of water is. Determine the difference between the temperature on your thermometer and 212 degrees (the temperature of boiling water at sea level). Then subtract that difference from the temperature that the recipe you are using calls for. The cooking temperature at higher altitudes is lower than it is at sea level (up to 10 degrees or more) and all thermometers are different. Most recipes are written for sea level. If you don't make the adjustment, your candy may be overdone. You may have to experiment.
Always use a heavy pan to make candy. Don't use a pan that has hot spots.
If the recipe calls for butter, use butter. Don't try to substitute margarine or another imitation butter.
Never, never, never scrape the sides of the pan as you pour it out. It can cause your candy to crystallize.
If there are sugar crystals on the side of the pan, wash them down with a wet pastry brush or wt cloth or paper towel a few minutes before the candy is done.
Butter and cream can both be frozen. When they are used in cooked item they work just fine. I haven't had great luck whipping previously frozen cream.
Candy gets very hot. Always use a wooden spoon with a long handle. Metal spoons can burn you and plastic mixing spoons will melt.
Always use high quality ingredients. Remember you candy will only be as good as what goes into it.
Always measure accurately. Remember that candy making is a science as well as an art. It involves chemical reactions and physical properties changing. Proportions matter.