How to Keep a Log Book

What makes an experiment a genuine work of science? An experimental procedure? Experimental observations? Maybe. But procedures and observations become useful (and interesting) to scientists only when both can be described with enough detail and precision to allow another scientist to repeat the full experiment.

Your lab notebook contains the descriptions of your experimental procedures and observations. It is the formal record of your lab work. As such, it should contain three types of information for each experiment:

  • A complete description of the procedure that you actually performed
  • A full account of the observations that you actually made
You should organize your information into several categories:
  • Methods and Materials (or Equipment) can usually be a simple list, but make sure it is accurate and complete. In some cases, you can simply direct the reader to a lab manual or standard procedure: "Equipment was set up as in the manual."
  • Experimental Procedure describes the process in chronological order. Using clear paragraph structure, explain all steps in the order they actually happened, not as they were supposed to happen. If your professor says you can simply state that you followed the procedure in the manual, be sure you still document occasions when you did not follow that exactly (e.g. "At step 4 we performed four repetitions instead of three, and ignored the data from the second repetition"). If you've done it right, another researcher should be able to duplicate your experiment.
  • Results are usually dominated by calculations, tables and figures; however, you still need to state all significant results explicitly in verbal form, for example: Using the calculated I gives R = 0.1244 ohms.

Graphics need to be clear, easily read, and well labeled (e.g. Figure 1: Input Frequency and Capacitor Value). An important strategy for making your results effective is to draw the reader's attention to them with a sentence or two, so the reader has a focus when reading the graph.