@sinituulia @laumapret my mother always had a bottle of spray starch to be carefully ignored while ironing clothing, so I have one too :D
lately when I want to feel fancy or I have to spend the whole day outside I've started to use it when ironing my linen shirts, and it does work in making them feel nice and crinkle less, but it doesn't make stuff significantly stiffer like I've seen in the videos and blog posts of people dipping garments in starch.
Maybe it's possible, if one uses *a lot*, but I'm not sure it's really designed for being used that way.
I'm not sure how much it costs, because I still have the bottle I stol… er, borrowed from my mother¹ a few years ago, since each shirt-ful takes very little, and I suspect that for this usecase it would actually cost less than making it at home from food-grade starch, as the latter needs to be made in a bigger batch (and it doesn't keep, not it's really safe to starch all of your clothing and store them starched long term, I believe).
I still want to try and make the liquid one to dip some collars and petticoats in, but there are only so many hours in the day, and starching looks like a couple days of commitment.
¹ we live close enough that she can easily take it back once ever couple years when she needs it :)