Watt was tasked with repairing a model Newcomen engine belonging to the University of Glasgow. This experience sparked his interest in steam engine technology and led him to identify the engine's inefficiencies.

Watt's key invention was the separate condenser, which kept the cylinder hot at all times, dramatically improving the engine's efficiency. This innovation avoided the repeated heating and cooling of the cylinder, which wasted vast amounts of energy in Newcomen engines.

Watt secured his first patent for the separate condenser, marking a crucial step in protecting his invention and enabling him to commercialize it.

The first commercial Watt steam engines are installed and begin operation. The initial engine was installed at the Carron Iron Works, near Falkirk, and others quickly followed.

Watt patented a method for converting the reciprocating motion of the steam engine into rotary motion, using a sun and planet gear system. This innovation greatly expanded the applications of the steam engine, enabling its use in powering machinery in factories.

Watt invented the double-acting engine, which applied steam to both sides of the piston, further increasing the engine's power and efficiency. This design became the standard for steam engines for many years.

To keep the piston rod moving in a straight line, Watt developed the parallel motion linkage. This solved a crucial engineering challenge and improved the reliability and efficiency of his engines.

Watt invented the centrifugal governor, which automatically regulated the speed of the steam engine. This innovation ensured consistent performance and was a crucial step toward automating industrial processes.

Watt's fundamental patents expire, opening the door for other engineers to further develop and refine steam engine technology. While he retired, his inventions revolutionized industry.