One of the victims was a 78-year-old man who was in the process of distilling a batch of the strong eau de vie with a colleague when the still exploded.
Ticino cantonal police said the boiler of the pot still rocketed through the roof of the shed where the alcoholic drink was being produced and landed 200 metres away.
"I thank God that I’m still alive,” the pensioner, identified as Achille, told the online website of the Blick newspaper.
He suffered second-degree burns to the feet and was treated in hospital.
“It could have been worse,” Achille said.
But the explosion has set back their plans for grappa production for a while.
Achille is a member of a cooperative that produces 4,000 litres of grappa a year, Blick reported.
Last Thursday morning, Achille and companion Domenico, 77, fueled the 50-year-old copper pot.
They decided to let off some steam and turned a tap.
“There was a bang,” Achille told Blick.
“I flew five or six feet away, slumped on the floor,” he said.
“We saw nothing — everything was full of steam.”
Domenico, who suffered a cracked rib, described the explosion as feeling “like a punch in the side.”
The estimated cost of rebuilding the shed and the still is at least 100,000 francs, which is money “we do not have,” Achille said.
But all the same, the pair are happy to have survived, even if the next round of grappa will have to wait.
Grappa is a grape-based pomace brandy that can contain up to 60 percent alcohol.
It is made by distilling the skins, pulp, seeds and stems left over from wine-making after the grapes are pressed.