DO THE BACK CUSHIONS ON YOUR CHAIR OR SOFA LOOK FLAT AND CRUSHED AFTER A FEW YEARS - WE HAVE THE ANSWER.
Unzip the cushion cover and remove the polyester filled interior, and you will find it is divided into two or three channels holding the loose polyester in separate compartments. (to stop the polyester filling from falling to the bottom). Open a side seam on the interior to expose the channels and as you pull out all the polyester filling you will find it has been 'matted' down with use. The old polyester needs to be pulled apart and fluffed back up (Carded is the upholstery name).When this is done reinsert the carded polyester into the interior. You will find you need some extra loose polyester to help fill the interior as the old polyester will have lost some of its body. Resew the opened interior seam by hand and insert the restuffed interior into its cover. It should be a tight fit - which is correct - as this means it will fill the corners correctly, and you will have a new looking back cushion.
Approximately 500grms to 1k of loose polyester is needed for each Back Cushion and remember the more you put in the firmer cushion becomes.
These instructions also apply to seat cushion and scatters cushions.