It ia a common practice to sprinkle some water on a strached cloth before ironing. How does it help?

Answer 1

It dissolves, or at least softens, the starch that stiffens the cloth, allowing the fibers to relax.

Answer 2

The cloth being iron needs no starch for water to help in ironing out wrinkles, the water erupts into steam when touched by the hot iron, the steam relaxes the fibres of the cloth and more heat sets them in a flat position.

Answer 3

Most strength of a material comes from Primary Chemical Bonds.

In addition the materials also have Secondary Bonds which contribute a smaller amount to their strength. (such as VanDerWaal and Hydrogen Bonds). If the material has not been disrupted it is these which produce small changes such as creasing.

When water is put on a material the Hydrogen Bonds decrease in strength by a factor of 80 - the dielectric constant of water. We smooth out the wrinkles and let the material dry flat so the bonds reform in the smooth ordered way we prefer.

This same process works with dented wood. Damp it, apply the iron and the dent will decrease.

Answer 4

The sprinkled water will turn to steam when touched by the iron and steam is used to relax fibers and reduce wrinkles. Additional ironing will dry the steam leaving the cloth as flat as the iron.

Answer 5

Interesting question. I believe that when the water turns to steam the expanding vapor separates the fibers allowing them to pass by each other with less friction thus flattening easier under the iron.