It isn't only welders that have heard the "wife's tale" and bought it hook, line, and sinker. I've had "inspectors" as well as engineers repeat it when I asked the question in each of my courses. The light usually goes on after I remind them of Freshman Chemistry 101 and mention "the by-products of combustion". Still, it can be unnerving to think that these  individuals haven't taken a second or two to think about what is being said and what is reality. Sometimes there is a disconnect between what we learn in school and what we see with our own eyes.

"If steel, nickel, aluminum, and other metals were porous, submarines would only submerge once and beer cans would leak!" is my usual response when people say the moisture that forms on cold steel when the preheat flame first plays against it is moisture driven from the pores. "Hogwarts!"

When I was taking a Physics course in college not that long ago, we had to calculate the heat content (in BTUs) of natural gas. We had a boiler fired by a Bunsen burner as the heat source. We measure the volume and temperature of the water going in and out once a steady state was reached. We also measure the volume of gas being burned. The professor had us place a small bowl under the burner. No one knew exactly why, but we did it. Once the flame was ignited, the bowl started to collect water. Several of the physics majors (this was a senior level course) informed the professor that the boilers were leaking and they needed different boilers.

The professor laughed and said to me, "Al, explain to these geniuses where the water is coming from!" He usually referred to me as his "little ignorant welder" in jest (I hope).

I responded that it was the by-product of combustion. He said, "Absolutely right. How can my little welder, who doesn't know enough to come in from the winter cold, come into this class and explain what you people have been studying for the last four years?"

Maybe as a welder I was able to see the relationships between what we studied in class and what I saw happening on the job site. I've always said that to be a successful welder you had to be observant and learn something new from every job you do. You can learn by attending the "school of hard knocks" or learn to read books and learn from other people's experience. Both ways will teach you what you need to know, but learning by reading is by far a much faster way to learn. I was a slow learner. It took me many years to get the education most engineers obtained in four years of college.

So trust me, I'm hold welders in high regard. However, to excel, you have to have an open mind that searches for the real reason things happen as they do. I'm delighted to see so many people come to the forum and participate, but I can't resist the urge once in a while to have a little good natured fun with the person asking the question. Again my apologies, no harm intended.

Best regards - Al