Paper and board in the same jar
On this page10
The requirement
NARA wants materials that are "lignin free, acid free, and either buffered with an alkaline reserve or of neutral pH". That is about the paper and board a collection sits in rather than about the container.
Which matters because jars contain enclosures
If the jar is the outer layer, the inner layers are paper envelopes, card inserts, 2x2 holders and labels. Those are in direct contact and they are in a sealed atmosphere with the object.
Ordinary paper and kraft are named to avoid
Along with glassine. Office paper and kraft are acidic and lignin-bearing, and glassine was a traditional philatelic material that has not aged well.
Buffered or neutral, and the choice is not always obvious
The guidance offers both. Buffering adds an alkaline reserve that neutralises acid over time, which suits most paper, and there are object types where an alkaline environment is not wanted. A conservator is the right person to ask about a specific collection.
Labels count
A label inside the jar is paper and adhesive in a sealed microclimate. Putting the label on the outside of the container removes the question entirely and is easier to read anyway.
So does the liner
The liner inside the closure is a material in the sealed space. Of the closures on this shelf, 63 carry an induction-seal liner, 42 F217, 31 PS and 19 PE foam, and 27 carry none.
Which argues for simplicity
A plain PP or PET jar, an inert enclosure, a desiccant, and the label on the outside. Every additional material inside is another thing that has to be inert for as long as the collection lasts.
Old albums are the common inherited problem
A collection arriving in a mid-century album is arriving in materials that predate all of this guidance. Rehousing is the single most valuable thing that can be done for it, and it is slow work.
Keep the old housing if it has information on it
Annotations, provenance notes and arrangement are part of what a collection is. Photograph or store them separately rather than discarding them with the acidic board they are written on.