Police said former pub DJ Ian Davison, 41, was plotting to use the killer chemical which was found in a jam jar in his kitchen when officers raided.
He ran a group of internet extremists known as the Aryan Strike Force with his 19-year-old son Nicky, who was convicted last month of preparing for acts of terrorism by downloading the guidebooks the Anarchist’s Cookbook and The Poor Man’s James Bond.
The teenager, of Grampian Way, Annfield Plain, County Durham, claimed he became involved in white supremacy to please his racist father. A jury took 50 minutes to convict him at Newcastle Crown Court.
Davison Snr, of Myrtle Grove, Burnopfield, County Durham, had already admitted producing a chemical weapon, preparing for acts of terrorism and three counts relating to possessing the terror handbooks.
Ricin is extracted from the castor bean and exposure to small quantities can be fatal.
The US Centre for Disease Control suggested that as little as 500mg – about half a grain of rice – could be lethal if injected or inhaled, and has no known antidote.
The father and son were both remanded in custody ahead of their sentencing at Newcastle Crown Court.
After Davison Jnr’s conviction, Detective Superintendent Neil Malkin said: “I have no understanding of their intended target.
“What I do know is the nature of the organisation and what it had pulled together in terms of the ricin, pipe bombs and the manuals can only give me concerns that the next step was to take it to the streets.”
The Aryan Strike Force was in the early stages of preparation when it was raided last summer, and planned paramilitary operations which aimed to topple the “Zionist” government.
Members believed themselves to be the most racist group in Britain.