Gently heat the oil and the wax together. This can be done in a double boiler or in a pot on very low heat.
(If using a double boiler be careful not to get water in your mixture.)
Leave to cool a little. (You can gently melt again if the balm solidifies.)
Pour into lip balm tubes and leave to set. Note: the mixture does not fill small kraft tubes all the way to the rim, leave 1-2mm free space at the top.
When the balm is cold, place the caps on the tubes.