text: To produce concrete, fresh plant material is extracted with nonpolar solvents.  On evaporation of the solvent, a semi-solid residue of essential oils, waxes, resins and other oil-soluble plant chemicals remains. 
  The solvent used for extraction must be chosen carefully regarding its polarity and boiling point. If the boiling point is too high, compounds that are readily deactivated by heat might be destroyed, leading to a loss of certain fragrance ingredients during evaporation.
  The resulting residue after evaporation consists mostly of heavier nonvolatile substances, which give concrete its "waxy" properties.
  Putting the plant materials under high pressure before treating it with solvents has been found to greatly increase the yield of the concrete. This is because high pressure causes the cells to burst, which allows the glucoside and diastase in the plants to react more freely.