Paper, defined.

Two different measurements, two different standards, routinely conflated on datasheets. Here is what each number actually means.

The hydraulic pressure that punctures a sheet. Why corrugated liner grades are specified by burst index, and what the numbers actually mean.

Micrometers, microns, and points. Why two papers at the same GSM can have completely different thickness — and why it matters.

The compressive strength test for corrugating medium. How the concora fluter works, what CMT values mean, and why flat crush resistance is the right metric for fluting grades.

ISO 3037 / TAPPI T811. The compression test for assembled corrugated board — not the individual liners or medium. Why ECT predicts box compression strength and what typical values look like.

The canonical reference for corrugated flute dimensions. A through N: what each profile is, how thick it is, how many flutes per metre, and what it's actually used for.

The wavy inner layer of corrugated board. What fluting paper is, how it's made on a corrugator, and why the wave geometry — not the fibre density — provides structural strength.

The single most important number on any paper spec sheet. What it measures, what it isn't, how to read it.

How much light passes through the sheet. Why show-through ruins thin paper. How it is measured and what ranges to expect.

ISO 12192 / TAPPI T822. A paperboard strip bent into a ring, then edge-compressed. Why RCT matters for both liner and medium, and how it relates to SCT as the industry convergence point.