I found some gorgeous vintage curtains and snapped them up for no money at all because they were filthy. They washed alright, so the fabric itself is fine. The lining however has really nasty water stains that did not come out and even stand out more now they are all cleaned up. So, I was looking into changing the lining but I'm short of time and I've only got a crappy sewing machine. In looking up how to do it, I came across easy ways to add a thermal lining to your existing (unlined I suppose) curtains. Has anyone done this? Does it get very bulky? I'm not looking forward to taking the old lining out and somehow messing things up so it would be quite quick and easy to add the thermal lining with and extra heading tape. Is this a good plan or is it going to be too bulky?