Jerry, it may be that the heads are thermoplastic but the very hot water definitely makes the red heads look like something has been “leached” out of them. They lose their shininess and seem kind of pitted.. In the case of my Bb, it cracked shortly after I removed it.
After that, it was just a tube. nyuk.
I have about 35 heads here that were removed in boiling water, and they all look fine, including the C heads I just mentioned.
Once in awhile, I do something to a whistlehead that spoils the surface shine. I’ve found that the plastic shines right up with a flannel cloth charged with jeweler’s rouge. If one ever does “blush” (that’s what that sort of whitening/dulling of shine is called) from exposure to boiling water, I expect it will respond to the same treatment. I’ll keep a watchful eye, but I’m not very concerned.
Best wishes,
Jerry
Never mind Ron,you now own the worlds’ first KNICK Oak whistle! 
I had one that wouldn’t come off.
I put it in the freezer overnight, ran hot water out of the tap and held the fipple under it a minute or so and it popped off no problems.
Perhaps shrinking the metal first is the secret.
I believe I’ve tried that, but without the same success. However, starting from frozen before heating does make sense because it takes the contraction/expansion cycle to the maximum effect. If I have trouble with the next C Generations I try to do using my current approach, I’ll freeze them and try again.
Best wishes,
Jerry
blowtorch against a generation???
one word:
eeeeeeeeeeeeedjitttt!!!
no offence 
That’s how I get the heads off my brass Gen Cs. I’ve tweaked several of those, like 10 or so. Gave a really nice one to StevieJ the other day.
Shoot, Bloo.
Ya been holdin’ out on us. Coulda saved a bunch of people a lota grief if you’d 'fessed up sooner.
Best wishes,
Jerry
Well, I don’t know how recently I’ve posted about it, but I have always insisted that the Cs are hard, not impossible to remove. The hot and cold thing is what has worked for me, and frankly just keeping at it. After I get a C-head off I will sand down the inside of the head; otherwise they tend to clamp up again when you slide them back on the tube.
And, hey, you coulda asked.
Well, OK.
What other secrets are you holding out on us? Time to ‘fess up now. I’m officially askin’ as per your instructions.
Best wishes,
Jerry
Now you guys tell me. The head is not supposed to touch the cup. I guess I will buy another Oak too. But I wanted a white cap now I have an excuse.
Ron
Hmmm, a blowtorch seems like overkill. A hammer worked fine for me.
Truly spoken by the man who ran his Gen over with a car (on my advice, no less). 
How do you play a blowtorch?
No doubt it improved it…
with hot lips baby, with very hot lips..
Final score:
Blowtorch = 1
Generation = 0
None taken, Amar. I actully felt like an eeeeeeeeeeeeedjitttt as I was pulling the melted head off the tube. It was a Homer Simpson moment. D-OH!
Paul, what in the world were you thinking? “What, plastic can MELT!!!” I think this is the most over-the-top attempt of tweaking I have ever heard of…
Jens
Feadog heads, both D and C, come off nice n easy after a few moments under running hot water. I’ve put a Feadog D head on my Doolin two-piece (which originally had the worst made head I’ve ever seen) and a Feadog C head on a Walton Mellow D tube (sounds nice… or at least it would in the hands of a competent whistler).
Gen Ds come off under running hot water too, but those Cs… I’ve never managed to get one off without damage. I prefer Feadogs anyway, so no biggie.
If the people who make the Generation Whistle read this message board, they must be getting a blast out of it. Here we are a group of people destroying their product in the process of trying to improve it! Has anyone ever tried to contact the manufacture of the Generation Whistle to see if the Whistle could be purchased without the head glued on? Just think, they could charge us more for a product that took less manufacturing steps!
This raises another question, who makes the Generation Whistle? Do they have a Web site, email address, or mailing address?
This was posted a while back, and saved in my bookmarks:
http://www.barnhide.co.uk/
They also make other instruments, like kazoos!