Lab notebooks and reproducibility

Why this matters

A result that cannot be repeated is not useful to anyone. In research, a colleague or a future version of you will need to know exactly what was done. In industry, especially in regulated labs such as pharmaceutical quality control, the notebook or electronic record is a legal document that inspectors can review. Good record-keeping is one of the first things a research supervisor or lab manager will judge you on.

Reproducibility, briefly

• RepeatabilityGetting the same result again with the same person, method and equipment.: the same person, method and equipment get the same result again.
• ReproducibilityA different person or lab, following your description, getting a consistent result.: a different person or lab, following your description, gets a consistent result.

Surveys of scientists over the past decade have found that many have tried and failed to reproduce someone else's experiment. Causes include unclear methods, unrecorded details (a different batch of a reagent, a different room temperature), selective reporting and simple errors. Clear notebooks address many of these.

What goes in a lab notebook entry

Institutions and employers have their own rules, which you must follow. Common elements:

For paper notebooks, common rules are: use a bound notebook with numbered pages, write in ink, never tear out pages, cross out errors with a single line so they stay readable, and date and sign each page. Many labs now use electronic lab notebooksDigital notebooks (ELNs) that add timestamps, audit trails and links to data files. (ELNs), which add timestamps, audit trails and links to data files. The principles are the same.

Worked example: improving a procedure

Weak entry:

Made the solution and measured it. Absorbance was 0.42.

Improved entry:

2026-10-23. Objective: check absorbance of a standard solution at 520 nm. Solution prepared by the lab manager from stock lot 4471 (see SOP-12, step 3), diluted 1:10 with deionised water in a 10 mL volumetric flask. Spectrometer ID SP-02, warmed up 20 min, blank: deionised water in the same cuvette. Three readings: 0.421, 0.418, 0.423. Mean 0.421, range 0.005. Room temperature 21 °C. Deviation: used cuvette B because cuvette A was scratched.

The second version lets someone else repeat the measurement and explains a result that might otherwise look odd later.

Note that this is a description of an entry only. Preparing solutions and using instruments in a real lab requires your institution's or employer's safety training, the safety data sheets for each chemical, and supervision.

Data and code count too

Modern physical science produces data files and analysis scripts. For reproducibility:

• Keep raw data unchanged; save processed data as new files.
• Name files consistently, for example 2026-10-23_SP02_absorbance_run1.csv.
• Record which script and version produced each result, and keep scripts under version control (such as Git).
• Write a short README describing where things are.

Common mistakes

• Writing it up later. Memory fails within hours; record as you go.
• Recording only the final number. Keep raw readings and every repeat.
• Leaving out the boring details. Lot numbers, instrument IDs and room conditions are often what explains a strange result.
• Hiding mistakes. Crossed-out errors and failed runs are part of an honest record.
• Ignoring local rules. Your lab's notebook policy and safety procedures come first.

Quick recap

• Reproducibility means someone else can follow your record and get a consistent result.
• A good entry has date, objective, materials with IDs, procedure, raw data, observations, deviations, analysis and conclusion.
• Keep raw data unchanged and link results to the scripts that made them.

Try it

Open the Do tab, write a procedure for a safe home measurement, and test it by having someone else follow it.