Mounting labels should serve two purposes - allowing them to be displayed nicely and keeping them safe, Unfortunately, very many of the methods used today by collectors will result in long term damage to the labels themselves.
The plastics used in albums and other products normally available at Stationers shops invariably contain acids (they are an essential part of the manufacturing process). Acid, like bleach, degrades ink pigments and causes them to fade. This process is irreversible and will persist as long as the plastic remains in contact with the surface of the label. It is therefore unwise to have labels in contact with plastic for long periods of time. These are acid-free plastics but these are very expensive and are not readily available. Paper too contains traces of acid and bleach; however these are present in minute quantities and it is usually quite safe to use for mounting; acid free paper is available for the purists. So use paper not plastic.
Labels are usually printed on paper which is a highly porous material. Without exception all oil based glues seep into the fabric of the label by a process of osmosis and diffusion. A natural consequence of such seepage is a staining on the front of the label which normally results in a very noticeable and ugly brown transparent stain. I have seen this on 1960's labels which had been mounted with Sellotape and the labels are totally disfigured.
Some time ago, I wrote to the British Museum Conservation Department and received a tale of woe about the irreparable damage to paper documents caused by oil based glues. Their strong advice was never to use them and to remove them from paper items not already damaged using solvents such as acetone, methylated spirits or white spirit.
These processes are slow and insidious and may not become evident over a 10 to 15 year timespan. They will however be very evident over a 20 to 25 year period. It is fortunate indeed that the older labels which are around were not originally mounted under plastic or using oil based glues!
So what can be done? One solution, and the only safe one I know, is to use water based gums made from animal or vegetable products. Water is a benign material so far as paper is concerned and the only problem lies with gums whose solid content is readily oxidized. However even here unless the label is totally saturated with the gum. such oxidation stains will occur on the back of the label only and will not be visible on the front
If labels are to be permanently mounted, suitable materials are starch paste or the original cow gum (but not the synthetic substance now sometimes found with that name). The gum or paste should be used sparingly and there is no real need to cover the entire surface.
If labels are to be moveable, a suitable way is to use good quality fully peelable stamp hinges (but do follow the instructions). I personally use two stamp hinges per label. This holds each label firmly and allows them to be rearranged as the collection grows.
I also mount labels from different breweries on separate sheets. Again, I would urge you to mount the labels on good quality, medium weight paper (around 100 gsm is suitable) and to use either lever arch files or spring binders as this allows pages to be inserted and your chosen order to be maintained I file alphabetically by brewery.
In my view, labels should be mounted in ways which allow a future generation to enjoy them. Please consider carefully whether the method you use to mount them will allow this or whether it will result in long term damage and decrease their value and appeal. It would be unfortunate indeed if this generation of collectors disfigured the very items they collect