Washing: Your curtains got dirty from just dust or perhaps someone spilled something on them. Now if they are your favorite, be on the safe side and get them dry cleaned. Often times even if a curtain says machine washable, they really aren’t. Or if they are, make sure they don’t go through the normal cycle. The delicate cycle will always be your best bet even if they are extra dirty. Not 100% sure why a lot of curtains say machine washable just to turn out not to be. You can tell after a washing if the colors have faded or you have small pieces of fabric missing. Very little damage will likely occur if it does but its still best to be careful. Some curtains will however rip and destroy themselves but those almost 99% of the time will say Dry Clean Only.
Drying: Then the dryer after cleaning. Make sure to always use just non-heated air especially if you have a thermal backing on the curtains. Soundproof curtains have such a backing and if you put these in the dryer they will likely melt and you’ll have ruined curtains afterwards. After all these backings are usually a type of plastic that melts really quickly. Plus with little room in the dryer there’s a good chance the curtain won’t move around enough to evenly distribute the heat. Instead you’ll have one part heat up a lot more than the others. If something starts to smell, turn off the dryer immediately!
After Cleaning: You may notice that after cleaning your curtains that they do not smell like the fabric softener or even the washing liquid you used. Sadly you can’t prepare for this happening besides unless you just do dry cleaning. The best option in this case is just let them hang and wait as the smell will go away. Otherwise a few squirts of febreze will help out greatly!
Keep those curtains clean and smelling fresh!