Otty Bamboo Charcoal Mattress Topper Review
A foam topper with bamboo charcoal in it, and the charcoal is doing considerably less than the marketing implies.
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Verdict
A foam topper with bamboo charcoal in it, and the charcoal is doing considerably less than the marketing implies. The topper is fine. The claim attached to it is the kind of thing this site exists to unpick.
Buy it if
Your mattress is sound but too firm, and you are buying the topper rather than the charcoal.
Avoid it if
You are buying it for odour control or moisture, or you sleep hot. Foam toppers make warm sleepers warmer.
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| Specification | Detail |
|---|---|
| Type | Foam topper infused with bamboo charcoal |
| The charcoal claim | Odour absorption and moisture control |
| The mechanism problem | Activated charcoal works by surface area contact with air |
| What it does not change | Support, or a sagging mattress |
| Heat | Foam adds insulation. It will make a warm sleeper warmer. |
The scores
A competent foam topper with a claim that does not survive examination.
Fair for a foam topper. You are not getting value from the charcoal.
Foam toppers soften a firm mattress effectively, which is the job.
Adding foam to a bed makes it warmer, not cooler.
A topper does not provide support. Scoring it otherwise would mislead.
Reasonable life. Toppers take concentrated wear and none last forever.
Otty's standard terms.
Why infused charcoal does very little
Activated charcoal genuinely absorbs odours and moisture. It is used in water filters, extraction hoods and air purifiers, and it works.
The mechanism is surface area. Activated charcoal is riddled with microscopic pores, giving an enormous internal surface, and molecules adhere to that surface as air or water passes through it.
That is where the bedding version falls down. Charcoal infused into foam is encapsulated in the foam. Air is not passing through a bed of charcoal; it is moving slowly around foam cells with charcoal particles trapped inside them. Most of the surface area that makes charcoal work is not in contact with anything.
The quantities are also small. A few percent by weight of charcoal in a foam layer is not the same order of magnitude as a filter cartridge.
So the honest position: it is not nothing, and it is far less than a filter, and if odour is your problem a washable protector and washing your bedding weekly will do vastly more.
The bigger issue is that foam toppers warm you up
| Type | Softens | Effect on heat |
|---|---|---|
| Memory foam | Strongly | Makes you warmer |
| Micro-spring or foam cylinder | Moderately | Neutral to cooling |
| Latex | Moderately, with bounce | Neutral |
| Wool | Mildly | Regulates moisture |
Softening is the easy part and every topper does it. The heat consequence is what people get wrong.
A foam topper on an Otty hybrid is a particularly awkward combination, because Otty's whole argument is a 16 centimetre spring layer moving air. Putting foam on top of it cuts you off from exactly the thing you paid for.
Measure before you buy any topper
The 25 millimetre rule
A topper changes firmness. It does not change support.
If your mattress has a dip of more than about 25 millimetres, a topper will follow that dip within a few weeks and the money is gone. Lay a straight edge across the mattress and measure the gap at its deepest point.
And plan how you will stop it sliding. Elastic corner straps, or a deep fitted sheet sized for the mattress plus the topper together. A 28 centimetre mattress with a 5 centimetre topper needs a 33 centimetre sheet.
A correction worth making
Commonly repeated, and wrong
Bamboo charcoal in mattresses, toppers and pillows is sold on activated charcoal's genuine ability to absorb odour and moisture, and that ability depends entirely on air passing through an exposed bed of it. Charcoal infused into foam is encapsulated inside the foam cells, so most of the surface area that makes it work is never in contact with anything, and the quantities involved are a fraction of what a filter cartridge contains.
Should you buy it?
Reasonable as a foam topper if your mattress is sound and too firm, and buy it for the foam rather than the charcoal.
If you sleep warm, buy wool or a micro-spring topper instead, particularly on an Otty hybrid where foam on top blocks the airflow that was the point of the mattress.
Questions people ask
Does bamboo charcoal in a mattress work?
Far less than in a filter. Activated charcoal absorbs odour and moisture by air passing through an exposed bed of it. Infused into foam it is encapsulated inside the foam cells, so most of the surface area that makes it work is never in contact with anything.
Should I put a foam topper on a hybrid mattress?
Not if you bought the hybrid for its temperature. A foam topper sits above the springs and cuts you off from the airflow that was the point of the mattress. Wool or a micro-spring topper softens without that penalty.