Sean McNulty, 26, will be sentenced today by Mr Justice Stephen Mitchell.
He showed no emotion and sat down in the dock as the jury of five women and six men announced their verdict after nearly eight hours of deliberation. But he smiled as he was led to the cells flanked by prison officers.
McNulty, a construction worker from North Shields, Tyne and Wear, had denied conspiring with a person or persons unknown to cause explosions with intent to endanger life between January and June last year.
McNulty took part in bombings at the Esso oil terminal in North Shields and the British Gas depot at Redheugh on Tyneside on the same night in June last year.
Fibres from his clothing and footprints linked him to the blasts, the court was told. The prosecution had also alleged McNulty had been involved in causing an explosion at the Esso plant the previous April, but the jurors could not agree any decision about this allegation.
In the June attacks, one bomb blew a hole in a gas holder containing 1.4 million cubic feet of methane gas, setting it on fire. British Gas staff and firefighters managed to prevent an explosion and the fire burnt itself out, although about 400 people were evacuated from nearby houses.
The same night, two more devices went off within minutes of each other at the Esso terminal. The bombs both contained more than a kilo of Semtex. They ruptured pipelines and an oil tank, but fortunately all were empty, Nigel Sweeney, for the prosecution, had told the court.
He said a bomb component recovered from each site showed the devices were the work of the IRA.
McNulty had a fanatical hatred of the British and gloated when he heard that British soldiers had been shot, the court was told. He had been under surveillance by MI5 and Special Branch before and after the bombings. He had been captured on film by a petrol station video camera which showed him in his car less than half a mile from the gas works less than 15 minutes before the device was timed to explode.
When police examined McNulty's car while he was in Ireland, after the bombings, they found traces of Semtex. Traces were also found at a house he was known to visit on Tyneside.
When he was arrested on his return from Ireland the print from the right boot he was wearing matched imprints found next to a hole cut in the perimeter fence of the Esso terminal and used by the bombers to gain access. Fibres on the cut wire also matched trousers he owned.
McNulty's former girlfriend, Amanda Johnson, 24, the mother of his nine- year-old daughter, told of his IRA allegiance when she appeared for the prosecution. She said that when British soldiers were shot or killed 'he said it served them right'.
Although born in Britain, McNulty kept insisting he was Irish, said Miss Johnson. He had increased his interest in Irish affairs after they were stopped by an RUC patrol after attending a wedding in Co Tyrone, she said.
In a bag he took with him when he worked away from home she found a pile of newspaper cuttings about bombings and shootings in Ireland.
'I put them in the bin, I told him what I had done, I said 'the shit is in the bin'.'
He had been under surveillance by the security services after he was seen with IRA suspects.
Mr Justice Mitchell excused the jurors from jury service for life, thanked them for their care and patience in a case 'saturated by detail'.
Detective Chief Superintendent Barry Stewart, of Northumbria CID, said later: 'I am delighted that the combined resources of the security services, the Metropolitan police and the Northumbria police after a long inquiry and investigation in difficult circumstances have happily achieved this result.'