Irish physicist John Tyndall developed tyndallization, a method of fractional sterilization that uses repeated heating to destroy microbial spores. The process is named after him and became an important response to problems that simple boiling could not solve.
Tyndallization typically heats a material near the boiling point, lets it cool and incubate, and repeats the heating over several days. The first heating kills ordinary bacterial cells, while some heat-resistant spores survive. During the interval, spores germinate into heat-sensitive cells, which later heating can destroy.
Tyndall’s work also clarified why some supposedly boiled broths still spoiled. He investigated airborne particles and showed that dust could carry microorganisms. His findings strengthened Pasteur’s challenge to spontaneous generation and helped explain the survival of bacterial endospores.
The method is now largely obsolete because autoclaves provide faster and more reliable steam sterilization. It remains historically important and can still be useful for some heat-sensitive materials when pressurized equipment is unavailable.