Interlining is a layer of fabric that is sewn between the face fabric and the lining of window treatments.

Interlining (or Bumph or Bumf) is hidden by the outer layers of the curtain – even though you can’t see it, adding an interlining could mean the difference between your drapes being plush, full and beautiful – and being limp and listless, wilting and without substance.

Bumph (also sometimes referred to as Bump) is one of the most common fabric used as an interlining.  It is bulky and flannel-like, with a brushed surface that gives it a lofty and substantial feel. 

Each layer of fabric creates an insulating air pocket, reducing heat transfer between indoors and outdoors.