To remove wax from cast iron holders, place the candle holder upside down on a stack of 3-4 paper towels in your oven at 210 F for 30 minutes. Remove and wipe away any additional wax with a clean paper towel. For hard to reach cavities use a Q Tip.
Once the holder is cleaned with no wax residue, apply a thin layer of cooking oil and remove any excess with a lint free cloth. Then crank the oven to 350 degrees F and then cure for another 30 min. These 2 steps should restore the holders to their original rich black colour.
If there is rust on the surface, soak in a mixture 50% water and 50% vinegar for 1-3 hours. Check the progress each hour and remove as soon as the rust disappears to avoid damaging the cast iron. Clean with cold water and then dry with a lint-free cloth. Never use dishwashing liquid on any cast iron as it may lead to rusting.
To clean simply wipe with a wet cloth and rub with salt, rinse with warm water and dry immediately. If there are signs of rust then wash with water and then sprinkle with baking soda and let it sit for an hour. Then rub off the rust using a scouring pad, rinse and wipe dry with a clean cloth. To prevent further rust, wipe using a cloth to wipe the surface with a light cooking oil and finally rub off any excess.