I remember seeing this excuse used in film and television when a girl wanted to blow off some guy who just asked her out on a date.
How is that a reasonable excuse? Granted, I have short hair and it takes me all of 60 seconds to wash my hair, but how long does it take to wash a two-foot, flowing mane?
As a guess, this probably dates back to before hair dryers for the home were available.
Long hair would take some time to dry.
Quite a long time if you don’t have internal hot water on tap, and have to boil up the water on the stove to get any sort of decent temperature for your bath. Which I imagine would have been the case for a lot of people when this excuse first started to be used.
Also, it takes forever for the stuff to dry. I have long thick hair and it takes a good two hours for it to dry fully, in the absence of a hairdryer. If you wanted to do anything complicated with it, like dry it in curlers it would take even longer, plus you’re much less likely to be willing to hit the town with it still wet.
I think (and I have often pondered it myself) that it goes back to previous days when women didn’t wash their hair as often, presumably before showers were common; I remember references in slightly older books to girls washing their hair at the sink every Saturday night, for example. So washing your hair was an event separate from bathing, and combined with the fact that most women had long hair, it must have been a bit of a production. (When were blowdryers really common? A quick google puts it at 1920, but that seems a bit early to be a household staple…)
But I assumed it was meant as an obvious blow off because if you wanted to go out, you would wash your hair earlier.
Also, I think a few generations ago, washing hair was something that was done separately from regular bathing, at least for women. Whenever I visited the 'rents and had to borrow shampoo, they didn’t keep it in the bathroom, but rather by the kitchen sink.
The house I grew up in, which was built in the 1920s, had a bathtub in the bathroom but without a shower head. To wash your hair, you either dunked your hair in the dirty bathwater, shampooed, and dunked again to rinse; or washed it in the sink.
At the time that was a popular excuse, a woman’s hair was styled. It wasn’t just washed and then left hanging. And it was only washed when it was time to rebuild the do. So washing was just the first step in an elaborate process that could take hours.
I have longish hair, and it takes me ages. Shampoo (it’s hard to reach my scalp through all that hair) twice, conditioner (got to get out every tangle), rinsing out every last sud- and then, when I get out of the shower, it takes hours to dry. That is, I can’t stand still long enough to blow dry my hair, so I just usually just put it in a pony.
Ouch, poor pony.
Before I cut all my hair off I had the same problem. In high school, I’d wash my hair in the morning out of necessity, and then really my only choice was to pull it into a ponytail and run off to school. Eight hours or so later I’d get home, let my hair down…and it would still be damp. Long, thick hair is such a pain.
My hair and my SiL’s hair are down to mid-shoulderblades. On 30C weather, it takes me about 10’ to shower and wash it, about half an hour for it to dry. Takes her about 1h for the same. I can go out about 5’ out of the shower; she is in a foul mood for days if she hasn’t been able to do the whole treatment.
I have very fine and abundant wavy hair which I don’t blow dry, straighten, curl or dye. She has thicker wavy hair which she straightens and dyes. She refuses to believe that the reason people compliment her on her hair when it’s wavy is that, amazingly enough, it looks good on her! (Imagine that, her hair looks good on her)
I can sympathize. In college I’d shampoo my long, thick hair before bed and go to bed with a damp head - even in winter, our dorm rooms were heated hot enough to run around in a T-shirt and shorts - and it’d still be fairly damp when I woke up in the morning.
In hot weather, this can be a feature, not a bug. I have been known to pile my hair up in a bun, then deliberately soak it for its long-term cooling properties
(less useful in these days of ubiquitous air-con, but still occasionally pulled out of the bad of tricks)
Well how about that. Thanks folks.
Yep - it’s not the washing time itself that’s a bitch… it’s usually everything after the washing that takes the longest.
I’ve been “blessed” with a head full of thick, curly, abundant hair. When I wore my hair waist-length, it would take approximately 30 minutes to wash and condition, and then another 3 hours to dry off. That’s three and a half hours before I’m fit for public consumption again.
Sure, I could use a blow-dryer to speed up the process, but it would still take 20-30 minutes to blast it to some semblance of dry… or up to an hour if I used a diffuser or did a blow-out to straighten my curls.
And that’s with a “wash and wear” cut, which requires minimal fussing to be presentable. Consider that about 50 years ago, any self-respecting girl would need to style and set her hair post-wash (roll it around curlers, coil it into pin curls, or whatever else have you), and it’s not all that unreasonable to estimate that someone like me would have needed the better part of an evening to deal with hair washing.
It took me three times from the same young lady to figure that out when I was thirteen. 
I have really thick hair, so I usually just wash it at night and go to sleep and wake up with dry hair.
Washing and pincurls or rollers or what have you…it was a major event back in the day.
(Sidebar: If I go to bed with wet hair, I’d have a lethal case of bedhead the next day.)
This is still the case for me today. I don’t like blow dryers–they make me hot and they make my scalp sweat. Plus, my hair is quite curly if I let it air dry. Sometimes I flat iron it, sometimes not.
I always thought the whole “I have to wash my hair” bit came from the days of styling/beehives and plastic curlers, as lissener said. Then it became the ultimate kiss off line (once hairstyles changed and dryers became commonplace)–a nasty way to tell a boy you weren’t interested in him.
RE the 1920s hair dryer. I think that means that weird looking bag apparatus that was attached by a hose to the dryer, not a hand held blowdryer. That type of dryer was popular up until the late 70s–Carol the Receptionist is shown using it on The Bob Newhart Show back in the day… I remember when blow dryers were the newest thing (and curling irons. And my older sisters used to literally iron their hair on the ironing board. Handheld flat irons weren’t around yet).
I feel old.
ETA: I do the same cooling thing in summer. I often wet my hair down and then French braid it–I stay cool all day.
In the beloved 1956 teen novel Fifteen by Beverly Cleary, Jane washes her hair before her big date with Stan, and her mother remarks, “Why, Jane, I thought you washed your hair the day before yesterday.”
Just to chime in with what others said…
My mom had thick hair down to her butt in the 60s. She lived in a house with no shower, just a bath tub - and also has 4 sisters. She was in to “big” hair. After washing it in the sink, she’d curl it around empty orange juice cans (you know, the concentrated stuff) and go to bed, so she could do a bee-hive in the morning.