Look a little closer
See the mechanism
Pressure brings two coatings together
Read the diagram steps
Before pressure. The back of the upper sheet carries capsules containing a color former. The receiving face below carries a developer. Intact capsule walls keep the color former apart from the developer.
At the written line. Writing pressure breaks local capsules. Released color former contacts the developer and produces a colored mark on the receiving sheet. The paper is not transferring a layer of carbon.
Original enlarged two-sheet CB/CF section. Capsule dimensions, spacing and layer separation are exaggerated; the schematic shows the selected color-former/developer construction.
Diagram basis: Koehler: CB, CFB and CF coatings.
Sources: Koehler Paper
The reaction happens between facing coatings
The upper sheet carries capsules on its back: CB means coated back. Writing pressure bursts capsules along the pen stroke. Their contents reach the developer on the lower sheet's front, called CF for coated front. Color forms where those materials meet.
Sources: Koehler Paper
Middle sheets receive and pass on the mark
For several copies, the middle sheets are CFB: coated front and back. Their fronts receive a mark from above; capsules on their backs supply the next sheet. The order keeps the reacting faces together.
Self-contained carbonless paper is an exception. It carries capsules and developer together in a front coating, so an ordinary top sheet can transmit the writing pressure.
Sources: Koehler Paper
The thing to remember
The pen supplies patterned pressure; the coatings supply the copy.
What this example leaves out
The diagram enlarges one conventional CB/CF interface. A CFB middle sheet adds another receiving and transferring interface. Formulations and usable copy counts vary.
Sources & further reading
Source access dates are listed below. Manufacturer descriptions and patents support the specific constructions described, not every product.
- How carbonless paper work ↗
Koehler Paper · Retrieved 2026-10-17 · Capsule rupture, reacting CB/CF layers, CFB middle sheets and self-contained exception.
Conventional stack and separately labeled exception; formulation/copy limits not inferred.
