A young Irish industrial designer may have solved the perennial problem of how to produce the perfect soft-boiled egg.

Ben Harris, from Killiney, Co Dublin, said the trick is to boil the egg at a constant temperature so as to allow the white to coagulate while the yoke remains runny. He said that for the perfect soft-boiled egg, the water temperature had to be maintained within a three or four degree range.

Mr Harris said his new "PerfEGG" device maintains the water at a temperature of around 70 degrees for eight and a half minutes.

The device, which contains a number of computer chips, can also be adjusted to produce a hard-boiled egg.

Mr Harris (22) has just graduated in industrial design from Brunel University in London. "I love soft-boiled egg with toasted soldiers but I get so frustrated if I get the timing wrong and the egg is too hard to dip my soldiers in. My design solves this problem," he said yesterday.

There has been some interest in marketing the new device but no deals have been agreed, he added.

Ironically details of the device were revealed as it emerged yesterday that as a result of separate invention, consumers may soon just have to look at the shell to see when the egg is done to their liking.

Lion Quality Eggs in the UK is developing an invisible ink logo which appears on the shell in black when the egg is done.

Logos, which respond to heat, will be adapted so they they appear at the correct time for soft, medium or hard-boiled eggs. A Lion spokeswoman said the project had been launched in response to a large volume of queries from people asking how to properly boil an egg.

"We had a lot of inquiries from people which sparked an interest in the industry. We said, OK, this is a big issue - people can't even boil an egg," she said.