Many makers use bonded blackout interlining in roman blinds, placing the blackout layer against the back of the face fabric. This means the side turnings and hems can be herringbone stitched to the ‘fleecy’ interlining layer without piercing the blackout. After folding the face fabric around the bonded blackout, the lining with rod pockets is added to the back as usual.
A good colleague kindly shared her excellent method for joining the bonded interlining for larger blinds. This is ideal when it can be railroaded so the join is placed at the top or bottom of the blind away from the rod positions.
These instructions place the extra section at the bottom of the blind.
Cut your blackout bonded interlining slightly longer and wider than your blind measurements, cut your additional section to join on - it should be long enough to include a 2cm overlap in length. Allow slightly more than required overall in the width and drop - it will be trimmed back later.
Lay the bottom edge of the main section so it's nearest to you, gently pull about 2cm of the wadding away from the blackout lining across the width.
Pin back the lifted wadding, pinning into the wadding only so that there are no holes made in the blackout. Add 2 lines of narrow double-sided sticky tape across the blackout layer.
Place the additional section of bonded interlining on top of the double-sided tape lining side down (ensuring it is level) and gently press to make sure it sticks all the way across the join.
Fold the lifted wadding down over the additional section and press gently (this helps the double-sided tape stick the layers together).
Measure and mark the finished width of your blind, carefully herringbone the join across this width through the interlining only so that the blackout is not pierced.
Trim the bonded blackout to the size of your finished blind, most people choose to cut it to the blind’s finished width and drop. Lay the blackout layer on the face fabric (blackout to rear of face fabric), neatly herringbone the bottom edge of the bonded interlining across the fabric hem fold (through interlining layer only). Some makers also herringbone the top edge in place for extra ‘hold’, although this can also be achieved when securing the top fold of fabric to attach the Velcro. Turn the blind side hems over the bonded interlining and repeat the herringbone stitching.
Then follow your usual making method to add the lining and complete the blind.
High quality double-sided tape is available from the MyDecozo online shop.