Practical laboratory classes are organized through the Biochemistry Department Teaching Lab. This is located in the basement of the Hopkins Building, Welcome Wing. Generally, there are two practicals running simultaneously Monday-Friday throughout term. The timings of these practicals can differ though they often last the full day (with some time for you to grab lunch). The practical organizer will generally ask for a full week's commitment so this can be a large time commitment for a postdoc. However, you will get paid extra for any demonstrating that you undertake, the pay rates change every year but are generally around 15-18 pounds an hour. Remember, you will get taxed on this. The amount paid will be taxed as normal an included in your salary a couple of months after you demonstrate. Often you will not get paid for demonstrating till the end of a term.