Title: Is Worf's Hair naturally curly or straight?
Tags: star-trek;star-trek-tng;star-trek-ds9;worf
Question: looking at different pictures of Worf we see that sometimes his hair appears to be naturally curly/wavy, and at other times its straight.
Do we know if it is indeed naturally curly, or is it straight with a perm(anent?
Comment: Well I'd call his hair wavy. My hair is straight until it gains some length, then it gets wavy. I guess that really means it's always wavy, but you can't really tell until it's long enough to see the waves.

Comment: Worf is Frieda from Charlie Brown!

Comment: @Escoce Bottom Left and Top Right are basically the same hair styles but with completely different results. Safe to say Worf perms his hair!

Comment: I guess this means that Worf either spends some time straightening his hair, or some time crimping it. This is fantastic.

Comment: Neither. It's a wig. Or the humidity levels on the Enterprise are *very* poorly controlled.

Here is the accepted answer: Though I don't think there's an ironclad proof one way or another (unless it comes from one of the books), I think the evidence suggests it is naturally curly but that he has it straightened.
We know from Schisms that Worf makes regular trips to the barbershop, at least while serving on the Enterprise. While only the length of his hair is addressed in the episode, knowing that he has it cut (and that he cares about its appearance, warning Mot not to take off too much again) makes it extremely plausible that he would straighten or curl it too.
The reason I believe it is naturally curly and he straightens it, as opposed to the other way around, is when we see him with curly hair. I believe the top right image in your question is the best indicator, because this is a screenshot from Insurrection, in which Worf (and others) are experiencing the rejuvenating effects of the planet within the Briar Patch. (He had to deal with a Klingon pimple in an earlier scene.)
Certainly, we see Worf with both straight and curly hair in situations where he has access to 24th century comforts, but this is to be expected. (People change their hairstyles periodically, and Worf in particular struggles with his identity as a Klingon in a human environment throughout the franchise.) But I don't know of a time when he was without the comforts of the Federation and still has straight hair. (The exception being that if he goes into a situation with a straightened pony tail, it appears to stay that way if he doesn't touch it.)
Comment for this answer: You think the rejuvenating effects affect hair, which is dead?
Comment for this answer: @ThePopMachine, we know that at least hair growth is influenced by the planet, as Picard is the fist bald man seen there in some time. Maybe putting the curl back in his hair is a stretch, but so is pretty much every bit of sci-fi technology throughout the franchise. In any event, this is still a clear-cut case of Worf "roughing it" as they lead the Ba'ku to safety on foot.
Comment for this answer: growing new hair over a few weeks is a totally different thing than changing existing hair.   I happen to think your conclusion is probably right, but I just don't think the evidence is there.
Comment for this answer: @ThePopMachine  The planet also affected everyone's mood and mindset.  A meticulous Klingon officer might get a little less strict about straightening his hair when he's riding a teenage hormone wave.  It does, for example, seem a little less tidy and well-maintained in that image.
Comment for this answer: There were a few times when we saw Worf outside of the comforts of the Federation. 'Redemption pt2', 'Birthright pt2', and 'Rightful Heir' in TNG, Also several episodes in DSN while he was serving on the Rotarran, as well as 'Penumbra' and 'Till Death Do Us Part' while in the escape pod and later while in Breen/Dominion custody.
Comment for this answer: In the pictures with straight hair, it still has some texture/barely-contained frizziness. I think Worf simply has his hair blow-dried straight.
Comment for this answer: @Xantec, what I stated was "I don't know of a time when he was without the comforts of the Federation *and still has straight hair.*" Other than when he goes in with his covert ops look (straightened ponytail and black clothes, as in Birthright"), do you have an image of Worf with straight hair in one of these episodes?
Comment for this answer: @Josh My mistake. Reading comprehension failure.

Here is another answer: I agree with @Josh that Worf's hair may be naturally curly if we look at the family lineage.
Mogh (Worf's father)
Seems quite curly (or atleast fuzzy).
Kurn (Worf's brother)
Definitely curly.
Young Alexander (Worf's son)
During his time on the Enterprise, he may have also visited the barber quite often like his father, hence the straight hair.
Older Alexander (Worf's son)
After leaving the Enterprise, he not have had time (or perhaps no longer wanted) to style his hair anymore. So ends up looking fairly curly.

Here is another answer: I have a theory.
Keratin is a protein that is a major building block in hair and fingernails, and it is also used to straighten hair when added in salon treatment processes.
From Wikipedia:
Keratin is one of a family of fibrous structural proteins. Keratin is
the protein that protects epithelial cells from damage or stress that
has potential to kill the cell.
If the rejuvenation planet is constantly refreshing cells, then the body may have no need for keratin and might halt production of it, thereby resulting in curlier or wavier hair for those under its effects.
Comment for this answer: he has had both, outside of insurrection.
Comment for this answer: This is more of a comment for an existing answer than an answer in it's own right.
Comment for this answer: Do Klingons have keratin? Or what is their equivalent? You can't assume human physiology in an alien species.

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