Catering staff are among 100,000 workers at universities and higher education colleges taking part in a nationwide protest over pay and conditions.
The industrial action, which started last week with a protest day of demonstrations and leaflet-dropping, is being co-ordinated by six trade unions, including Unison, the TGWU and the GMB, which represent most of the catering workers involved in the protest.
The unions are calling for a raft of improvements, including the introduction of a minimum wage of £11,000 by 2002 and a new pay structure as recommended by the Bett Report into pay and conditions, which was published last year.
They also want national negotiations for minimum terms and conditions governing areas such as holiday pay and sick pay, which they claim will provide a fairer deal for members on a nationwide basis.
Unison national officer Bruni de la Motte said that two-thirds of the union's 60,000 members had voted in favour of taking industrial action.
"It's goodbye to goodwill - that is the idea of the action," she said. "By working to rule, members are refusing to do extra."