how to modify a water bottle so that it will keep cold water in it for a longer time?

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knife1415 years ago
Old motorcycle trip tip: Fill the bottle halfway and freeze it. When you get ready to use the bottle, fill the other half with water. Then wrap the outside of the bottle with 5 or six layers of paper towels and tape them on with masking tape. The water will stay cool for a long time.
Kiteman5 years ago
I smell homework...
rickharris5 years ago
Almost fill the bottle - Put in freezer over night - Make sure the bottle will stand the freezing and leave room for the water to expand.

As the water melts you can drink it - The core will stay frozen for several hours.

You can add insulation if you like.
Three words... Spray Foam Insulation.

FoolishSage5 years ago
If you add any kind of insulation to the bottle it will keep colder for longer. Examples of insulation are things that are poor heat conducters (like rubber), things that imobilise air (like foams) or a larger bottle to hold a vacuum.

If you expect the bottle to stand in direct sunlight you can also add a reflective material to the outside to minimise radiative heat absorbtion.
Libahunt5 years ago
Simplest and multi-use: wrap it in a towel.

More permanent: make a sheath that has some fluffy material (air layer) inside and nearly air-tight layer outside. A reflective surface on the outside (or in any layer faced out) helps additionally.

Idea is the same as thermos, only difference that the heat is outside therefore reflection must be directed that way (thermal radiation). For insulation vacuum would be best, but nearly impossible to make. Air that is trapped in some fluffy or bubble-holed material is good. As oppeosed to air that can freely move inbetween some vertical walls and effectively transport heat from one wall to another .

And if you plan to keep the bottle in open sunlight make it light-coloured or reflective for sure, so it doesn't absorb so much thermal radiation.
Insulate the outside.