The water heater springs a leak. The plumber disconnects and removes the old tank, then installs and connects a new one. Applied science in action. Liquids wick into paper towels. Ground water rises through the cells of plants. A combination of surface tension (due to cohesion within a liquid) and adhesive forces between the liquid and adjacent surfaces acts to propel the liquid through capillary action — provided the gap between those surfaces is sufficiently tight. Plumbers count on this ability of liquids to flow in narrow spaces without the assistance of external forces — even in opposition to gravity — as they follow these commonsense instructions.
In copper plumbing systems the gap between tube and fitting is about 0.005". A good solder joint begins with cleaning the outside of the tube and the fitting socket. Use sand cloth, abrasive pads or steel brushes to remove all oxides and surface soil, to enable molten solder to flow and form intermetallic bonds with the two copper surfaces. Insufficient cleaning invites joint failure, but if too much material is removed, the resulting loose fit will prevent the capillary action needed to make the joint. A thin, even coat of soldering flux applied to both tube and fitting socket will prevent the copper surfaces to be joined from re-oxidizing during heating, and promote their wetting by the solder.
Once cleaned and fluxed, insert the tube all the way into the fitting and remove any excess flux with a rag. With a torch-flame held perpendicular to the tube, evenly preheat and test-touch the solder to the joint. If it doesn’t melt, continue the heating — but don’t overheat, causing the flux to burn. At the melting temperature, apply solder around the edge of the fitting while continuing to heat the socket’s base to allow molten solder to flow into the joint by capillary action, whether the solder is being fed upward, downward or horizontally. It is best to allow the soldered joint to naturally cool before any remaining flux is wiped off with a wet rag.
The science and similarly commonsense instructions are equally clear regarding Covid-19. It spreads through droplets of moisture exhaled by infected people, which is why thoughtful people wear face masks in public. Most of the exhaled droplets are heavy enough to drop to the ground within 2 yards or so, which is why we keep a minimum social distance of 6 feet. Some nanodroplets remain airborne longer, so we avoid crowded indoor places. And because the virus can survive for a time on surfaces and objects we touch, we wash our hands with soap and water often, to help avoid transferring the virus to our faces (especially the eyes, nose and mouth).
Preventing the virus’ spread could help stop it altogether. Studies suggest that if we all just wore masks, we could stop the virus’ spread within weeks. Stay at home orders and temporary lockdowns could have a similar effect. We know this because some countries have been quite successful shutting down, testing, contact-tracing and isolating the infected. As of November 20, Taiwan had only 500 confirmed Covid-19 cases and 7 deaths since the beginning of the pandemic. Of New Zealand's 1883 total cases, only 65 active ones remain. China, where the virus originated, reported 308 infections on November 20. Of those only one case is serious. In contrast, over the same period the US has amassed more than 11 million Covid-19 cases and more than 265,000 deaths — both numbers growing beyond control.
A poor solder joint may leak and damage a house, but failing to slow Covid-19’s spread results in tens of thousands of daily deaths and damages a whole economy. I don’t know of any plumber’s marches against having to clean and flux a pipe joint before soldering it. But even as the Covid-19 death toll rose past a quarter-million Americans, many denied even the virus’ very existence. “They tell you there must be another reason they are sick. They call you names and ask why you wear all that ‘stuff’. Because they don’t have COVID. Because it’s not real” — posted South Dakota ER nurse Jodi Doering recently about many of her Covid-19 patients.
I won’t speculate as to why people rise up against scientific evidence, mask-wearing advice, even to deny the obvious existence of this deadly pandemic. But I wonder how many Americans would elect to hire a plumber who does not understand how to do a solder joint? What about leaders who deny or politicize clear scientific evidence and mislead millions to do likewise? How could they rescue a badly ailing economy wrecked by a powerful microscopic enemy that only science can defeat? Surely, we can do better.