Stainless steel Can be an amazing material. Stainless was invented less than 100 years ago around 1924. Columbus, an italian bicycle tubing manufacturer makes the best Stainless steel bicycle tubing in the biz. Stronger than anything else out there it can be drawn very thin while remaining super strong making for a light weight responsive ride. Here are a few process shots of the bike in progress. When welding stainless steel you must "back purge" the welding area. This creates a shield that protects the weld from Oxidation, (the presence of oxygen that creates a build up of contamination). Here you can see how the frame is plumbed as gas is fed into the frame creating the shield. At the welding area the torch creates the shield on the outside at the welding area. Once the steel has cooled (about a second or two), the steel is not susceptible to the same oxidation. The shielding gas used is argon. A non flammable gas that is just a bit heavier than air.