Supposing you iron clothing, or even just sit on it the wrong way, a crease forms that holds in place for a while. How does this work? What semi-permanent change to the fabric is keeping it bent in that way?
When you iron something, you’re applying heat. That heat breaks the bonds holding the polymers making up the fibers in place. The fabric cools and the bonds reform and hold the fabric in the new position. The other common mechanism is water. Cellulose-based fabrics have hydrogen bonds help lock the fibers in place. Water can get in there and change the hydrogen bonds which creates a new shape.
Presumably the bonds broken & reformed to create these ‘creases’ cause an increased amount of wear & tear on the fabric, and thus eventually lead to damage to the garment?
I know that I’ve noticed some very old clothes that start to wear out along the crease lines.
Probably. I wouldn’t be able to begin to guess how much stress creases put on the fabric.
It doesn’t need to be chemistry. It can just be the threads in the weave sliding around.
This is an interesting thread.
It’s a new wrinkle.
Hopefully people won’t be just making up answers out of whole cloth.
That’s what I’ve heard. This is also the mechanism between hair irons, as opposed to perming, which creates permanent sulphur bonds. I guess this is why ironing clothes works so much better with water.
Also if you don’t have access to an iron, just pat or spray some water on to the garment, and wear it. The bigger creases will fall out as it dries.
Which is also why hanging a garment in a hot and steamy shower stall (or using an actual clothes steamer if you have one) helps de-crease it.
The same effect of water breaking hydrogen bonds between adjacent molecules in fabric fibers, which allows the fabric to be re-shaped (i.e., allows wrinkles and creases to be formed or removed), is the reason that many non-woven fabrics have to be “blocked” or stretched into the desired shape after getting wet. (This comes to mind readily because I just finished washing and pin-blocking about twelve feet of hand-crocheted scarves and cowls prior to putting them in summer storage. :))
The presence of water (from washing, sweat, atmospheric humidity, whatever) causes the fibers to release their bonds with neighboring molecules and bond with water molecules instead. Then when those bonds break as the water evaporates, new bonds are formed between the fibers. So if the fabric is re-shaped while wet—either desirably, by ironing, gravity, blocking, stretching, etc., or undesirably by folding and creasing—it will retain that new shape when it dries.
Does hanging it in the sun in-crease it?
A very closely related thread with an extensive answer by Blake.
As long as you don’t try sitting down.
Heh heh, basically, yes. The drier the fabric becomes, the more “set” the wrinkles or creases that have formed in it will be.