How you store a coin after you acquire it determines whether it stays in FDC condition for decades or gradually degrades. The enemies are predictable: PVC plasticiser from cheap storage materials, humidity above 50%, skin oils from bare-handed handling, and temperature fluctuations that cause condensation inside containers. Understanding each risk and its solution takes ten minutes to learn and protects years of collection value.

Why PVC is the single biggest storage threat

Until the 1990s, soft plastic coin flips were the standard storage method sold at most numismatic shops. Most were made from PVC (polyvinyl chloride). PVC releases a plasticiser over time that migrates to coin surfaces, leaving a characteristic green, greasy film that is chemically bonded to the metal. Once PVC damage appears, it cannot be reversed without further damaging the coin. Any soft, slightly sticky plastic flip should be assumed to contain PVC and avoided entirely.

The safe alternatives are Mylar (biaxially oriented polyethylene terephthalate) and non-PVC polypropylene. Both are rigid, chemically inert, and available from reputable numismatic suppliers. Packaging should state "archival quality" or "acid-free, PVC-free" explicitly.

Hard capsules: the best protection for individual coins

For valuable and high-grade coins, hard plastic capsules offer the best individual protection available outside a professional grading slab. A capsule is sized to a specific coin diameter: 17.5mm for a 1 Lira, 23.3mm for a 10 Lire, 27.8mm for a 100 Lire Minerva, 29.3mm for a 500 Lire Caravelle. The coin sits suspended inside, with no surface touching the holder. Reputable brands include Leuchtturm and Air-Tite.

For the most important pieces, double-box the capsule inside a rigid outer case and store in a stable drawer away from external walls. Professional NGC and PCGS slabs provide equivalent protection alongside a certified grade.

Albums for series collecting

For organising complete series by year, coin albums with individual pockets are convenient and show gaps at a glance. Verify the album is PVC-free and acid-free before purchase. Polypropylene albums from Leuchtturm or Numis are appropriate; vinyl albums are not. Each coin should fit snugly without rattling or touching adjacent pieces.

What the storage environment must provide

Relative humidity between 30% and 45% is the target range. Above 50%, silver coins develop toning spots and copper pieces begin to corrode. A climate-controlled interior room is ideal. A garage, cellar, or attic is not, regardless of packaging quality, because temperature fluctuations cause condensation inside any container.

Silica gel packets placed inside storage boxes absorb ambient moisture and extend microclimate stability. Replace or regenerate them every 6 to 12 months by drying in an oven at 120°C for one hour. A small packet costs under one euro and is the simplest active humidity control available.

What never to use or do

  • Rubber bands — rubber contains sulphur, which tarnishes silver within months
  • Kitchen bags or standard ziplock bags — not inert, trap moisture
  • Tissue paper or newspaper — acidic and abrasive over time
  • Bare fingers on coin surfaces — skin oils cause permanent toning marks on FDC and SPL coins within weeks
  • Cleaning before storage — cleaned coins are always worth less than original-surface coins regardless of appearance

Handle every coin by the edge only. For FDC and SPL pieces, cotton gloves are the appropriate standard. This one habit, consistently applied, prevents the most common source of grade reduction in privately held collections.