AK-BİLWe do not sell beds. We sell what is inside them.
AK-BİL has made the core in Kayseri since 1998 — the foam, and the adhesive that holds it. The trade calls the core the Kern: Federkern, Kaltschaumkern. We call it çekirdek. Everything a buyer touches is upholstery. Everything a buyer feels is this.
The core
I
The core
A foam is a solid that has learned to be mostly air.
Geometry
- Cell
- 300–800 µm
- Faces per cell
- 13.7
- Pentagonal faces
- 50–57 %
- Three walls to an edge
- 120°
- Four edges to a vertex
- 109.47°
At 45 kg/m³ a polyurethane foam is ninety-six per cent gas. What remains is a lattice of struts, and every property the sleeper will ever notice — the firmness, the recovery, the way the surface returns when the shoulder lifts — belongs to that lattice and not to the polymer.
Raise the density and the struts thicken. That is all density has ever meant.
Surface energy sets those two angles. No one designs them.
A pentagon is the one shape that cannot fill space by repeating. A foam is what a material does when it must fill space with a form that refuses to repeat.
II
The law
Stiffness follows the square of density.
E* / Eₛ ≈ C (ρ* / ρₛ)²
Gibson and Ashby, 1982. Cell walls bend long before they compress, and bending stiffness scales with the square of the strut’s section. Twenty per cent denser is forty-four per cent firmer.
On logarithmic axes the square law is a straight line and its slope is exactly two. Nothing done to the polymer moves it.
- Density
- + 43 %
- Modulus
- + 104 %
50 kg/m³ against 35 kg/m³.
This is the only number on a foam worth arguing about, and it is the number the trade keeps to itself.
III
The section
Eight strata. Two hundred and forty millimetres.
| Stratum | Material | mm | kg/m³ |
|---|---|---|---|
| Ticking | Knitted polyester jacquard, quilted | 12 | — |
| Bond line | Hot-melt adhesive | 1 | — |
| Viscoelastic | Memory foam, open-cell | 40 | 50 |
| Bond line | Hot-melt adhesive | 1 | — |
| Support foam | High-resilience polyurethane | 30 | 35 |
| Spring unit | Pocketed steel · seven zones · 2.0 mm | 140 | — |
| Bond line | Hot-melt adhesive | 1 | — |
| Base felt | Needle-punched non-woven | 15 | — |
| Overall | 240 | — | |
Seven zones
One thousand and eighty-eight pocketed coils in a 160 × 200 core. Every one identical, every one sewn into its own pocket, so that each answers to the load directly above it and to no other.
Endurance
EN 1957. A 140 kg roller crosses the surface thirty thousand times, and then the height and the firmness are measured again. Adjectives are not admitted to this test.
- Cycles
- 30 000
- Height loss
- 3.4 mm
- Firmness loss
- 4.1 %
IV
The bond line
One millimetre decides the other two hundred and thirty-nine.
A mattress is sold on its foam and bought on its springs. It lives or dies on the millimetre between them.
Hot-melt adhesive, laid down as a controlled web at 150 °C. Upward it wicks into the open cells and interlocks. Downward, against the pocket textile, it can only wet. A bond line run too thin starves and lets go at the shoulder, where the load is worst. Run too thick it becomes a plate, and stiffens the very layer the buyer paid to have soft. One millimetre, held.
This house began in 1998 making adhesive. The foam and the steel came afterwards. We have been at the bond line longer than we have been at the bed.
V
The memory
It is not memory. It is delay.
Memory foam does not remember your shape. It forgets it slowly.
An elastic foam answers a load at the speed of the load. A viscoelastic one answers late, and how late it answers is the whole of what is being sold.
Two specimens stand on one plinth. Press them both.
Two specimens · one gesture
High-resilience
Press and hold
Viscoelastic
Press and hold
It answers you, and it answers back. Let go and it is already where it started.
It answers late, keeps the hollow, and takes six seconds to forget you.
Same gesture. Two materials. The difference between them is a time constant.
The loop
Load it, unload it. The two curves do not meet.
Compress a foam and you do work on it. Release it and the foam does work on you. In a high-resilience foam those are the same number: the unloading branch lies on the loading branch, and the drawing closes on itself.
In a viscoelastic foam the two part. It comes down a lower line than it went up, and the area caught between them is work that never came back. It left as heat.
This is why memory foam does not push back at your hip, and why an ordinary foam does. It is not being gentle. It is being lossy.
High-resilience
Viscoelastic
The temperature
The glass transition of this polymer is put where your body is. Below it the chains are locked, and the foam is glassy and firm. Above it they slide, and the foam is rubbery and soft.
So the foam is hard where you are not and soft where you are. Nothing switched it. You are what is heating it. Your body is the input.
- Glass transition
- 25–35 °C
- Hysteresis loss
- 62 %
- Recovery
- 6 s
Warming it is the same as loading it slower.
Time and temperature are one axis, wearing two names.
The material is accounted for. These are the beds it is in.The collectionThe collection
- 01TITAN MEMORY POCKET
- 02PERLA
- 03BLACK PEARL PILLOW TOP
- 04MEDICATED
- 05ROYAL RESSORTS
- 06SUPREME
- 07ACTIV MATRATZE
- 08OXYTECH
- 09COPPER
- 10DRY & SOFT PILLOW TOP
- 11ELEGANCE H2O
- 12GO GREEN
- 13BAMBOO
- 14MIDI 15 CM
The bed is what you see. The core is what you sleep on.