A coin's grade only goes one way after minting, down. Good storage can slow that process to near-zero; bad storage can wipe 30% off the value of a £500 coin in a year. Here's the UK collector's approach.
What to store coins in
Cardboard flips with mylar windows, the default
A folded card with a clear mylar (not PVC) window on each side. £0.10–£0.15 each. Fill in grade, date and source on the card in pencil. Good for coins up to ~30mm diameter, which covers most UK coins up to crown size.
Hard plastic capsules, for anything special
Air-tight acrylic shells sized to specific denominations. £0.30–£0.80 each. Essential for silver/gold coins (to prevent toning), high-value pieces, and anything above £50 market value. UK-standard sizes: 20mm (5p), 23.43mm (£1), 27.3mm (50p), 28.4mm (£2), 38.6mm (crown).
PCGS/NGC slabs, for £200+ coins
Professionally graded coins come in tamper-evident holders. Don't crack them out, the grade certification is part of the value.
What NOT to use
- PVC-lined sleeves. Cheap "coin books" with clear plastic pages often use PVC which slowly releases acids. Green sticky residue on a coin = PVC damage, and it\'s permanent.
- Direct skin contact. Skin oils and salt etch silver and copper within weeks. Handle coins by the edge only, ideally with cotton gloves.
- Damp environments. Bathrooms and garages are no-go. Silver tones blue-black in high humidity; copper turns red-brown.
Humidity and temperature
Target: 40–50% relative humidity, 15–22°C, stable. A cheap digital hygrometer (£10) tells you if your storage area is safe. Silica gel sachets in your coin box keep humidity down. Avoid attic (temperature swings) and basement (damp).
Where in your house?
A wardrobe or under-bed drawer in the warmest, driest room is ideal. Bank safety deposit boxes are overkill unless you're storing £5,000+ pieces. Home safes work fine but avoid ones with silica-drying agents that expire, replace sachets annually.
Insurance
Most UK home contents policies cover coins up to £1,500–£2,500 total. Above that, specify individual items with the insurer, you'll need professional valuations. The MyCoinage insurance PDF report (Pro feature) produces a valuation document in the exact format insurers accept.