Couple questions then a questionable answer.
How old is it? What material? How clean is it?
In the old days I would simply say get a
Hudson sprayer, fill it with warm water and , starting from the top, lightly mist the surface. The
cyc will sag a
bit more then as the water evaporates it will tighten back up. So here's the caveats: If done incorrectly this could cause your
cyc to spot, water stain or destroy it's flame retardant application. If it's an
IFR fabric, you don't have to worry about the flame issue. If it's old you are really going to want to vacuum or gently
beat the dirt out of it. If you don't clean it first it will spot and make brown stains everywhere.
If it's not an
IFR fabric check the date on the flame tag. if it's past it's effective date then clean it. Then you may want to look into "Flame Check". It's a new favorite product as it mists on but provides a 5 year flame retardant. you don't have to get materials as wet with Flame Check as you do with other products.
This process is fraught with difficulties and dangers. You have the potential of "salting out" the flame retardant. You have the potential of staining the curtain and it may not fully shrink for you.
If you can safely raise the
dead hung top pipe a couple inches, do it that way. You could also try just steaming it, but again, you want to make sure it's clean first and Steaming will take a very long time and it's very persnickety. too much steam you salt out or water stain, too little and nothing happens at all.
