Machine Direction (MD)
Definition
The direction parallel to paper travel through the papermaking machine; cellulose fibres preferentially align in this direction, making machine-made paper stronger and less extensible in MD than in the cross direction; useful for linking or separating sheets from the same production batch.
- Definition
- Direction of paper travel through the papermaking machine
- Fiber alignment
- Preferential along MD
- Mechanical effect
- Stronger, less extensible than cross direction
- Forensic use
- Linking or separating sheets from the same batch
Common questions
How can machine direction help link or exclude documents?+
Comparing the MD orientation and associated fibre or tear characteristics of two sheets can help determine whether they came from the same roll or production batch, or from different paper stocks entirely.
Why does MD affect how paper tears or folds?+
Because cellulose fibres align preferentially along the machine direction during manufacture, paper tears more cleanly and resists stretching along MD but tears more raggedly and stretches more easily across it, a property examiners can use when assessing torn or folded document evidence.
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