Short answers, pulled from the story.
Puddling was a step in the manufacture of iron that replaced older methods like potting, stamping, finery forges, and bloomeries. The process involved heating molten pig iron in an oxidizing atmosphere to decarburize it until workers gathered it into balls called puddles. These balls were then shingled and rolled using grooved rollers on existing rolling mills.
Abraham Darby II converted pig iron to bar iron in 1749 though no details survive about his method. The Cranage brothers achieved experimental success using a coal-fired reverberatory furnace and received patent number 851 in 1766. Peter Onions at Dowlais constructed a larger reverberatory furnace in 1783 and began successful commercial puddling with patent number 1370.
A two-man crew consisting of a puddler and helper could produce about 1500 kg of iron during a 12-hour shift. Workers stirred molten metal using long bars called rabbles equipped with hooks on one end while exposed to intense heat and fumes. The physical demands caused most puddlers to die in their 30s because automation proved impossible due to the need for human judgment.
Joseph Hall invented wet puddling at Tipton also known as boiling or pig boiling by adding scrap iron and iron scale containing oxides like FeO. He partnered to establish Bloomfield Iron Works at Tipton in 1830 and the firm became Bradley Barrows and Hall from 1834 onward. This method reached nearly 100% yield compared to dry puddling which yielded one ton of iron from 1.3 tons of pig iron achieving 77% efficiency.
German chemists developed a modification around 1848 at Haspe Iron Works in Hagen to produce steel instead of iron. Commercialization spread across Germany France and the UK during the 1850s with mild steel production via puddling occurring circa 1850 in Westphalia Germany. Low Moor Ironworks adopted the method in Bradford Yorkshire England in 1851 while Loire valley operations began using it in 1855.