List of what you will need before you start:
Bar of paraffin
Metal wick holders
Double boiler with a pouring lip
Stubs of colored candles
A lot of these items can be found at your local craft store, like Michael's or Hobby Lobby, etc. Use stubs from colored candles to make candles in various shades.
Clean shells in water with a few drops of bleach. Rinse well with cool water. Let fully dry.
Break apart the paraffin block into smaller chunks. (You can do this with a sharp knife, but be careful.)
Melt them in the top of the double boiler by heating the water below to a slow simmer. Use the paraffin as is, or you may wish to add bits of colored wax for different color combinations. Try a variation and see what you like.
This is a great way to use up your excess candle wax that wasn't burned away completely. Experiment with color blends.
Cover a steady surface with newspapers, or whatever you have handy. Balance one of the shells on a small cup and slowly pour in the melted wax. Immediately place the wick and wick holder in the center of the shell. Leave wax to cool for at least 30 minutes so all the wax will harden fully.
Light up and enjoy your beautiful sea shell candles! Great to remember your trip to the ocean, or bring a bit of the coast to wherever you are. Would be fun to use anytime, or for a party or get together.