Wilkinson was born in Washington, then in County Durham. He was the fifth child of John Wilkinson and his wife, Margaret Thompson. His mother died soon after his birth and his father in 1704, leaving him to be brought up by his elder brother John, a woolmerchant. He seems to have received some basic education before being apprenticed a foundryman, probably at the nearby Swalwell works. There, he established himself as a highly skilled iron-worker, able to demand high wages.
Cumberland and Lancashire
Some time between 1721 and 1723, Wilkinson moved to Workington where he worked at the Little Cliftonfurnace which probably produced cast iron by smelting with coke. Here Wilkinson operated as a specialist subcontractor to the furnace. In 1735 he moved to Backbarrow furnace, which smelted with charcoal, buying iron from the firm and selling his own produce. He was an influence on John Wilkinson his son. In 1738 he patented a cast box smoothing-iron though it is suspected that he already knew that it was invalid owing to prior art. He went into production in partnership with his brother John but indulged in "creative accounting" to cheat his brother of the profits and the partnership folded. By now, Isaac was living in Cartmel, enjoying several business interests, including the Lowwood iron company. However, the Lowwood project ended in litigation when the weakness of his patent emerged and he accused the enterprise of poaching workers from his other enterprises.
In 1753, Wilkinson moved south to Bersham, near Wrexham in Wales. There he operated a furnace, the Bersham Ironworks, with his son John, Edward Blakeway and others. Wilkinson developed the business while maintaining his own subcontracted casting business. Another patent in 1757 was for a blowing-engine for blast furnaces, using columns of water similar to the trempe system, though it is uncertain how effective it was. Blakeway was declared bankrupt in 1759, his shares passing to Mary Lee who married John Wilkinson in 1763. This gave the Wilkinsons control of Bersham and the business flourished. Isaac patented a novel moulding process in 1758. Isaac's personal subcontract business was a source of continued tensions. Litigation against his partners, including his son, had started as early as 1762, being exacerbated by the slump in Bersham's business following the end of the Seven Years' War in 1763 when demand for armaments dried up. Isaac moved to Bristol and John ended up as the owner of the Bersham works.
