Card damaged by heat in a parked car

Left a card in my car during a hot summer day and came back to find it had warped. The deformation was worse than I expected from what I thought would be a brief exposure. Here's what happened and what I learned about card heat limits.

What heat does to polycarbonate cards

Polycarbonate begins to soften at elevated temperatures. Interior car temperatures can exceed 70°C (160°F) on a hot day — well above the point where polycarbonate starts to deform under its own weight. The card was sitting in a phone holder on the dash, exposed to direct sun, and it had warped into a slight curve within what I estimated was two to three hours.

PVC cards are even more heat-sensitive and will deform at lower temperatures than polycarbonate. If you're not sure which material your card is, assume it's vulnerable to heat and treat it accordingly.

The damage assessment

The warp was a gentle curve across the diagonal — not a crease or a crack, just a plastic that had settled into a new shape under heat and weight. The holographic overlay was undamaged visually. The barcode area appeared clean. Under UV the features looked intact.

Attempted recovery

Used the heat press method I'd read about — iron on lowest setting through parchment paper, immediately under weight while cooling. Three cycles reduced the curve significantly. After 24 hours under weight, the card was nearly flat with only a faint residual curve visible when viewed edge-on.

The recovered card scanned normally on multiple apps. The visual appearance was acceptable for practical use. However, I noticed under magnification that one edge of the holographic overlay showed slight bubbling where the adhesive had partially separated during the heat event. The bubble wasn't visible to the naked eye but it was there.

Don't store cards in vehicles during warm weather. A card case in a bag or pocket is sufficient for daily carry — the card stays at body temperature, which is well within safe limits.