MR sent this fascinating explanation of one reason the Allied bombing campaign was a bust with regards to inhibiting German aircraft manufacturing:
When I was in grad school I heard of the origins of CO2/Sodium Silicate core making in Germany during WWII. The fellow said we were bombing factories and foundries. My dad and later myself were metallurgists, both doing time in the foundry industry before branching out.
Coremaking….. cores make the hollow spaces inside castings, is heat intensive as it was done with oil bonded sands that had to be baked like cookies. Gas, coal, coke…..and big core ovens. A cupola to melt iron can be made from oil drums and bricks and the molding sands can be mixed with a shovel and rake, but you need ovens for cores. We couldn’t figure out how the Germans were making castings so soon after we bombed their foundries into the stone age.
After the war we found out that they had invented a core making process that did not need ovens or oil. Simple sodium silicate and clean sand. What the foundry men would do was take the coreboxes, the molds for the core..out in the cities and countryside. They taught the people to mix the silicate and sand and ram up the cores, then set them out in the air. In a few hours to a day the core would be hard as a rock…literally. The two halves, or more pieces, would be glued together and be ready to go. They had regular drop off and pick up routes and kept the German foundry industry humming.
Necessity, as is so often the case, proved the mother of invention. Given the dearth of invention in Silicon Valley of late, perhaps we should encourage the North Koreans to bomb the Bay Area.