Not only will the right chemical composition of a powder react to the right plastic causing deterioration of the powder, but so will exposure to light, as will humidity.
So you're saying powder will deteriorate in a plastic hopper/powder measure, but not in the plastic container in which it was shipped???
Cholla Hill: You're overlooking the key word in my sentence, "right". Plastics come in all forms of composition, some reacting to different solids/liquids, while not to others. Why can you put/store gasoline in a plastic gas can while that same gasoline in another plastic container not formulated for gasoline and the gas will eat right through the container. Same goes for gunpowder. Now I did read in the information I looked up regarding various powder hoppers made by reloading outfits that the hard plastic powder hoppers made today differ than those made in the years before. No date of change given, but all manufacturers and the powder companies all still say not to use the powder hopper as a storage facility, stating that some powders, depending on their composition will react at some point.
I bought an older Lyman orange #55 powder measure at a outdoor swap meet that had a line about 2/3 up from the bottom. The plastic below that line was discolored and there was small powder size dents all over inside the discolored plastic area. Someone had stored powder in the measure to long. Polishing with fine sandpaper and steel wool cleaned it up. Cholla, when I started reloading for metallic cartridges 41 years, 9 months ago (doesn't count years using a Lee handloader for 12 guage), everything I read then said not to store powder in a powder measure due to plastic/powder reaction, light deterioration, and the possibility of the powder sucking up moisture from humidity in the air, not to mention the safety aspect of the whole process.
Reloading like everything else is governed by rules, break them, ignore them, try to bend them, will always result in Murphy's Law taking affect. Ya, I say you've been 'lucky', glad you have been, but who's to say that somewhere in your 40 years of doing it 'your way' that there hasn't been some powder not meeting its full potential due to some deterioration along the way. Besides, how long does it take to empty that 'hopper'. Just sayin! No intention or desire to get into a online post 'war' with ya, not going to. Safe reloadin' and shootin' to ya and everyone. CC
Hey dutchy, no 'sweat' on asking questions or for help, we all need to. This forum has been pretty quiet lately, in fact downright dead. Needed some postin exercise anyway.