You can shrink 100% Polyester by dipping the 100% polyester in boiling hot water for a few seconds.
Under normal washing in hot water the Polyester does not shrink much if any but when you dip the Polyester in boiling water for a few seconds or so then it can and will usually shrink.
Polyester does not shrink in a normal hot wash.
However if you were to wash Polyester in a water temperature of 230 F degrees or higher then it could shrink.
If you wash Polyester in a hot wash and then dry it at a hot temperature then the Polyester may also shrink some but not a lot.
It usually takes effort to get Polyester to shrink.
Polyester can and will shrink in hot water.
That is if the hot water is hot enough.
For Polyester to shrink in hot water the water temperature must be at least 230 F degrees.
However if the water is too hot then the Polyester can melt because Polyester is a type of plastic material and not actually cloth.
You can also quickly shrink polyester in boiling hot water by dipping it for a few seconds but don't leave it in too long or it will melt.
you can shrink polyester in boiling water.
To shrink polyester in boiling water get the water to boiling and then take the polyester and get the polyester wet first and then while the polyester is still wet dip the polyester in the boiling water for a minute or so.
The way the boiling water shrinks the polyester is the boiling water breaks down the polyester fibers which causes the polyester to shrink.
When natural fibers and polyester is blended together the polyester can shrink much more and easier.
It can be hard to shrink polyester on accident but if you really want the polyester to shrink you can get the polyester to shrink.