Is plastic bottle bad for maintaining quality?

[NeoPTLD]

I put some water in a soda bottle so the gross weight is 400.00g. Repeatedly measured and it was at 400g at the time, but I noticed it lost about 100mg in about a week. Recalibrated the scale and it's still reading 399.90g. I gave it another week and it lost about another 100mg.

There is no hole and the lid is tightly on, so I think the vapor is diffusing out.

Doesn't this mean that smell from where you stored it and such can get in as well?

 

[blahblah99]

That's probably due to heat cycling of the bottle and causing air to escape out during the hot cycle.

Try the experiment again in a controlled temperature environment and report back, preferably below the dew point of the liquid (water).

 

[Billb2]

Most plastics are permeable to water. The relatively small water molecules move through the relatively large plastic molecules.

 

[Taejin]

i dont think the permeability of plastics is high enough that it would make a difference in the timeframe the OP is suggesting.

 

[KIAman]

Unless you sealed the lid, there is not such thing as a "lid is tightly on." Try melting or gluing the lid on the repeat your experiment.