The ritual of covering each other in foam is to honour the ‘academic family’ – the pairing up of first year students with academic parents.
Every year the ‘raisin weekend’ is held in the university’s Lower College Lawn.
'Raisin weekend' was once celebrated with a gift of raisins, now it's marked with a foam - A LOT of foam.
First year students give their raisins (or foam) to their elder academic parents as a thank you for their guidance.
In exchange, the students receive a receipt for their gift, traditionally written on parchment in Latin.
Ego civis (name of parent), tertianus/a (if you're a third year) or magistrandus/a (fourth year) huius celeberrimae universitatis Sancti Andreae, qui (father's degree subject) studeo, a te (child's name), meo/a bejanto/ina carissimo/a qui (child's degree subject) student, unam libram uvarum siccarum accepisse affirmo pro qua multas gratias tibi ago.