I need to make a flask to hold a decent amont of liquid and to keep it hot for long, help???????!!!
I once made one out of unfinished DWV tubing an some freeze plugs. DANG........i am steam punk?
As Steve asked, how much is "decent"? Ounces? Gallons? Cubic meters? It sounds like you want to know how to make a Dewar flask (Thermos bottle) from scratch. You might look up either of those terms on Wikipedia, and read through the description of their construction. Then decide whether you want to do it yourself as a learning project, or spend 10-20 dollars and buy one.
It WOULD be fun to speculate on making one....
Yes, indeed! I think for someone proficient in glass-blowing, it should be straightforward (not "easy," but there's not a whole lot of mystery, either). The two difficult steps, to my mind, would be (1) getting the inner volume of the vacuum vessel mirrored (silver or some other metal vapor deposition), and (2) doing the vacuum pump-down and pinching off the nipple. Once you have the glass vessel completed, putting it into a robust holder with a sealing cap is easy.
Are the damned great spherical lab "dewars" made of glass ? The London Science museum has Dewar's original I think - I'm not sure if it still has the cozy that his wife made to keep the cold in on it still.... Steve
Don't know for sure. The ~half-gallon "milk jug" ones we use for hand-carrying have glass cores (as I discovered by dropping an empty one off a storage cabinet as an undergrad -- luckily, the lab supervisor didn't charge me for it). I would think that using a metal core would lead to too much heat conduction around the material, and the vacuum insulation would be less relevant. Glass has a low conductivity, which makes it good for this kind of application.
I thought like you on metal, but there are a lot of metal flasks available these days, and I think the very thin neck section doesn't really move much heat - and you're winning on volume/surface area as you get bigger of course.
The mirroring shouldn't be too difficult:https://www.instructables.com/id/Make-Glass-Mirrors-With-Silver-Nitrate-Sugar-Am/ I'm guessing that a compentent lampworker would be able to seal the nipple pretty easily, too. Applying the vaccuum to the vessel and heating the nipple might even close it up automagically when the glass reached its flow point. That's a WAG, though.
You could insulate a container that holds enough liquid. But if you want a more useful answer to the question we need some more details. L
How MUCH liquid ?