The best sleeves: polyester (Mylar)
Polyester film is the standard for archival storage of paper. It is clear, stiff enough to support the note and chemically stable, so it won't react with the paper or the ink. Mylar is a brand name for polyester film. Currency sleeves sold as "Mylar D" or "archival polyester" are what you want.
Buy sleeves sized for the note. Small-size notes need a modern currency sleeve, while large-size notes need a larger one. A tight sleeve can bend corners as you slide the note in. One that is far too big lets the note shift around.
Polyester does build up static, which can catch dust. Handle sleeves with clean, dry hands and slide notes in gently along the long edge.
What to avoid
- Soft PVC holders: the floppy, slightly sticky vinyl sleeves and some older album pages. PVC releases plasticizers that leave a greasy film on notes. If a holder smells like a shower curtain, don't use it.
- Tape of any kind, including on tears. Tape stains paper and leaves residue that ruins a note's grade.
- Paper clips, staples and rubber bands. Clips rust and dent, staples leave holes, rubber bands rot and stain.
- Folding. Every new fold is permanent and lowers the grade. Keep notes flat from the moment you find them.
- Cleaning, washing, ironing or pressing. All of these damage paper and grading services will spot them.
- Writing on notes or on sleeves pressed against the note. Write on a separate card.
- Lamination. It can't be undone.
Humidity, heat and light
Paper absorbs moisture, swells and shrinks with every change in humidity. High humidity encourages mold and foxing, the small brown spots seen on old paper. Very dry air makes paper brittle. Preservation guidance for paper aims for a cool room at or below normal room temperature and fairly dry air, around 35 percent relative humidity. At home, a steady level somewhere below 50 percent is a practical target. Steadiness matters more than hitting an exact number.
That rules out attics, basements, garages and spots near exterior walls, radiators or bathrooms. An interior closet in the living space of a house is usually the best place. Keep notes out of direct sunlight and bright display lights, which fade inks and yellow paper over time.
Albums, boxes and safe deposit boxes
For a few notes, sleeves stored flat in an archival box work well. For a growing collection, a currency album with polyester pages lets you view notes without handling them. Check that album pages are labeled PVC free.
Safe deposit boxes are secure, but some vaults run damp. If you keep notes there, put sleeved notes in a sealed plastic box with a packet of silica gel. Check them once in a while and replace the gel when it stops working.
Handling notes
Hold notes by the edges with clean, dry hands, or with cotton or nitrile gloves. Don't bend a note to check crispness and don't flick or snap it. Lay it on a clean, soft surface when you take it out of a sleeve. Slide it back in rather than forcing it.
If a note is already folded, stuck to another or torn, leave it as it is. Unfolding a tightly folded old note can crack the paper along the fold. A dealer or conservator can advise on notes that need careful handling.
What about graded notes and framed notes?
Notes graded by PMG or PCGS Banknote come sealed in rigid holders. Leave them sealed, because cracking a holder voids the grade. Store the holders upright in a box made for them, away from heat and damp like any other note.
Framing a note for the wall is fine for a common keepsake if you use a UV-filtering glazing and a frame that holds the note without glue or tape. Hang it on an inside wall out of direct sun. For anything in the collector premium band or higher, display a good photo instead and keep the note itself in the dark.
Labels and records
Keep a simple inventory: type, series, denomination, serial number, condition notes and where each note came from. Photograph both sides. A record like this helps with insurance, makes selling easier and keeps family history attached to the notes long after the person who saved them is gone.
Frequently asked questions
What is the safest sleeve for paper money?
Polyester film sleeves, often sold as Mylar or Mylar D. They are clear, stable and don't release chemicals that damage notes.
Why is PVC bad for storing currency?
Soft PVC releases plasticizers that leave a greasy film on paper and can damage notes over time. Use polyester, polypropylene or polyethylene holders labeled PVC free.
What humidity should I store paper money at?
Cool and fairly dry, ideally somewhere around 35 to 50 percent relative humidity. Keep it steady. Avoid basements, attics and other spots with big swings.
Should I clean or flatten an old bill?
No. Washing and pressing damage the paper, flatten the original embossing and are easy for collectors and graders to detect.
Sources: Library of Congress: Care, Handling and Storage of Works on Paper · PMG Paper Money Grading Scale