I have a few banknotes and I placed them inside some banknote sleeves. Those sleeves come with 3 sides sealed, I sealed the 4th side as well by myself to fully enclose the note inside the bag. This makes the banknotes waterproof and scratch-proof. But is there any disadvantage about this method of preservation? Would it be better for my notes to sit in an open sleeve instead over the long term?
If there is even the slightest moisture inside the sleeve when you sealed it, there is no place for that moisture to go except for inside the note. I personally feel you should store the note flat, but leave the fourth side open. Any moisture (no matter how remote) can escape and shouldn't usually get back in.
Having said that, companies such as PCGS totally seal their coins and notes - however, I have a feeling they inject an inert gas inside the encapsulation to prevent moisture (if any) from affecting the note/coin.
