STON · Carrier register
Carrier dossier: Ceramic stone
A porous body that meters oil out through its whole mass rather than from a surface, which makes it the steadiest release in the register and the one least disturbed by humidity. It is also the only carrier that remembers what it was used for, and that has consequences.
By The Scent Desk·Published 2026-09-20
| Medium | unglazed porous ceramic or lava stone, 60-200 g, sometimes on a wooden tray |
|---|---|
| Release mechanism | open pores hold oil and meter it out through the whole body, not just the exposed face |
| Where it wins | slowest and steadiest release in the register, holds direction fidelity better than wax, reusable for years |
| Where it fails | porosity is a one-way door — a used stone keeps a trace of the previous scent, moisture discolours it |
| stone porosity pct | 18–42 |
| weight g | 60–200 |
| oil load ml | 3–8 |
| release days | 25–70 |
| re oil cycles | 6–20 |
| coverage m2 | 3–12 |
Porosity decides everything
A stone's release rate is set by its porosity and by how much of that pore volume is interconnected. The common bands:
| Porosity | Typical body | Oil load | Life | Suits |
|---|---|---|---|---|
| 18-24% | Dense ceramic | 3-4 ml | 25-35 days | Small spaces, close range |
| 28-34% | Porous ceramic | 4-6 ml | 35-50 days | Bathrooms, studies |
| 36-42% | Lava stone | 6-9 ml | 45-70 days | Living rooms and other large volumes |
Higher porosity carries more oil and releases it more slowly, but it also takes on water faster. Lava stone above 38% develops a water mark within two weeks at 80% humidity, which is why a bathroom wants 28-34% porous ceramic rather than the most open stone available.
Why it is steadier than a reed diffuser
A reed diffuser's output is governed by the evaporation rate at the liquid surface, and that rate moves a great deal with temperature and humidity. A stone's output is governed by diffusion inside the pores, which is far less sensitive to both. Measured in the same room with humidity swinging between 55% and 75%:
- Reed diffuser: output varies by about 28%
- Wax tablet: about 22%, driven by temperature
- Ceramic stone: about 9%
That is the whole argument for putting a stone in a bathroom or a kitchen, where humidity moves more than anywhere else in a home.
Memory, and the rule for changing direction
Oil that enters the pores never fully leaves. Even when the life is over and the stone reads as nothing, 15-25% of the original load is still in there. Two consequences follow.
- Topping up in the same direction is unproblematic. A stone takes 6 to 20 loads and improves with use.
- Changing direction requires 7 to 14 days of airing — seven for ceramic, fourteen for lava stone — so the residue can leave. Without it, old and new combine into a sweet, unidentifiable middle note that no amount of wiping will remove.
If a direction change cannot wait, the only reliable answer is a second stone.
Loading and topping up
- First load: apply with a pipette in a spiral from the centre outward. Never in one spot; it runs off the face before the pores can take it.
- Leave one hour to draw in, then wipe away the surface film with a dry cloth.
- Top up when the stone is silent at 20 cm, never on a calendar.
- Reduce each load: 5 ml first, 3 ml second, 2 ml third. The pores are partly filled, and repeating the first figure overflows onto the tray.
- Oil seeping from the base means saturation. Skip one top-up and leave it 24 hours before deciding.
Container compatibility and cleaning
- A glazed tray is mandatory. Bare terracotta, wooden surfaces and tile all draw water up into the stone from below, and a dark water mark appears within two weeks.
- Never wash it. Water enters the pores, drives the residual oil out with it, and leaves a permanent stain on the body.
- Dust with a dry brush, never a damp cloth.
- Store sealed when not in use, and air for a day before it goes back into service.
When not to choose it
- When output is needed quickly, for instance before guests arrive. A stone takes 6 to 12 hours from load to steady state.
- Where the direction has to change often. Every change costs 7 to 14 days of airing, and there is no way around it.
- Hanging installations. Stones run 60 to 200 g and break when dropped.
- Any position a small child can reach.
Refill and replacement
Load 3-8 ml into the unglazed face with a pipette, let it draw for an hour, then re-oil only when the stone reads dry at 20 cm.
Plans using this carrier
| Rooms | Rung | One fill lasts | Running cost |
|---|---|---|---|
| Bathroom | L2 | 38 d | CNY 16 |
Assembly, in order
- Load with a pipette, not a pour — Draw three to eight millilitres and apply it across the unglazed face in a spiral. A poured load floods the outer pores and leaves the centre dry for a week.
- Let it draw for an hour — Leave the stone face up for an hour before it goes anywhere. Handling it sooner pushes oil onto your hands and out of the pores that were supposed to hold it.
- Re-oil on dryness, not on schedule — Hold the stone twenty centimetres from your face. If there is nothing there, re-oil; if there is still something, wait. A calendar is a worse guide than your own nose for this carrier.
- Keep one stone, one direction — Porosity is a one-way door. A stone that has held a woody direction keeps a trace of it for life, which is why seconds sell cheap and why this one should not be re-tasked.