INVISIBLE ink used to be a party piece for mischievous school boys. Now it has become the weapon of choice for schools looking to outwit summer holiday burglars.
Canisters concealed in alarm-activated sprinkler systems stain the skin of intruders with ink that only shows up under ultra-violet light. The ink solution, called SmartWater, also carries a chemical code identifying the school, and can be used to mark property.
Heads in Bolton, Oldham, Sussex, Brighton and Nottingham have adopted the security system after it was successful in east Manchester. Some of the 20 schools in Beswick were experiencing 10 burglaries a year, but since installing the system three years ago only one break-in has been reported.
Steve Openshaw, crime reduction adviser for Bolton, said: "Schools become an adventure playground for some children during the holidays so we are finding innovative ways of preventing crime. We are installing the SmartWater devices covertly but advertising it to protect as many schools as we can."
There are already 2,000 schools in England using the system, which costs pound;750. Phil Cleary, the system's inventor, said: "Schools are particularly vulnerable because they are closed for the holidays and local criminals know where and when to attack.
"Often the police know who they are but have no evidence. Now we can provide a forensic link which proves their involvement."
However, David Leech, senior loss control surveyor for Zurich insurance, believes that basic security measures like wooden fences, bolts, chains and safes are the most effective deterrent for thieves.
He said: "Property markers are good once the items are retrieved but the police still have to catch the suspect before the ink wears out. The best security system is a basic fence. It may cost pound;110,000 but it pays for itself in the long run."