The smell lives in the cardboard and foam, not in the metal. So separate the car from its packaging first. The car usually needs nothing more than a gentle wash and a thorough dry; the box needs time in dry air alongside something that absorbs odour. Neither needs sunlight, bleach or perfume, all of which damage what they touch.
Musty means damp
That smell is the by-product of mould and mildew growing in material that stayed damp - which means the storage was the cause. Fix where the collection lives, or the smell comes back. The reasoning is in protecting collectibles from humidity, and where not to keep boxes in storing diecast long-term.
Check for mould before anything else
- Look for fuzzy white or green patches, black speckling, or brown staining that spreads from the corners.
- Handle it outside or in a ventilated room, ideally with gloves, and keep it away from the rest of the collection.
- Be honest about the box. Card with visible mould growing through it rarely recovers, and it can spread to other packaging. Photograph it for your records and decide whether it is worth keeping.
The car
- Take it out of the packaging and keep the two apart from now on.
- Wash gently in lukewarm water with a drop of mild dish soap, using a soft brush for panel lines. Method in how to clean dust off model cars.
- Dry thoroughly, especially around the wheels and axle slots, where trapped water starts rust - do diecast cars rust.
- Let it air for a day or two. Plastic interiors and rubber tyres can hold an odour after the metal is clean.
The box: what works and what does not
| Method | Verdict | Why |
|---|---|---|
| Airing in a dry, shaded, ventilated room | Works, slowly | Dries the card out without harming the print |
| Sealed tub with baking soda or activated charcoal, not touching the box | Works best | Absorbs odour over days to weeks; keep it in an open dish so no powder reaches the card |
| Silica gel alongside it | Helps | Pulls moisture out, which is what feeds the smell |
| Sunlight | Avoid | It kills the smell and fades the printed card - the most light-sensitive part of a collection |
| Fabric spray or perfume | Avoid | Masks rather than removes, and can stain or warp card |
| Vinegar wipes | Avoid | Adds moisture and acid to the material you are trying to dry |
| Ozone generators | Avoid | Ozone attacks rubber and some plastics - including tyres and clear parts |
| Freezing | Does not help | Does not remove odour, and condensation forms as it warms up |
How long: expect days for a mild smell and a few weeks for a strong one. Replace the baking soda or charcoal when the smell stops improving.
Foam inserts and blister trays
Foam holds odour far more stubbornly than card. If a foam insert still smells after a few weeks with an absorbent, replacing it with fresh, clean foam cut to the same shape is often the realistic answer. Clear plastic trays can be washed and dried like the car.
Stop it coming back
- Store inside the heated part of the house, off the floor and away from outside walls.
- Not in a loft, garage or damp basement. A basement can work if it is dehumidified - see displaying diecast in a basement.
- Seal dry, or do not seal. A box closed in a damp room is how this started.
- Store the car and the box separately if the box has ever smelled.
If you are buying
A musty smell on a second-hand lot is a record of where it was kept. Look at the axles for rust and the card for warping and staining before you agree a price - damp reaches those first.
FAQ
How do you get a musty smell out of old diecast?
Separate the car from its packaging. Wash the car gently in lukewarm soapy water and dry it thoroughly, especially the axles. Put the box in a sealed tub alongside an open dish of baking soda or activated charcoal for days to weeks, away from sunlight.
Does baking soda work on smelly cardboard boxes?
Yes, in a sealed container with the baking soda in an open dish rather than sprinkled on the card. Activated charcoal works the same way. Replace it when the smell stops improving.
Should I put a musty box in the sun?
No. Sunlight will reduce the smell, but it fades printed card, which is the most light-sensitive part of a collection. Air it in a dry, shaded, ventilated room instead.
Is the musty smell mould?
Usually, or mildew - it is a sign the material stayed damp. Check for fuzzy patches, speckling or spreading stains, handle anything visibly mouldy away from the rest of the collection, and fix the storage conditions.
Can I use an ozone generator on collectibles?
It is best avoided. Ozone attacks rubber and some plastics, which includes tyres and clear parts, so the treatment can do more lasting damage than the smell.