Here's a bit of engineering information about the development of The Cast Aluminum Stuffed Waffle Iron. Read on if you're interested: These three photos show its evolution. On the bottom left is one of my original prototypes. It was machined and then a nonstick coating was applied on its cooking surfaces. You can see quite a bit of discoloration on its outside surface that took place over time from its exposure to heat and flame. The photo above it shows a later prototype I built after having designed a scissor-like action for opening the center pan. It too was machined and given a nonstick coating. However, it was also anodized. Anodization is a process of thickening the natural oxide layer on the surface of metals to form a smooth, durable, non-reactive and corrosion-resistant coating. It is a common process used in aluminum cookware, mostly in pots and pans. You can see how little discoloration happened comparatively on this piece because of its anodized surface. The photo on the right is an off-tool model of the final design that went into mass production a few months ago. This model was machined like the other two (hence the term off-tool), but die casting would be used in mass production. Anodizing die-cast aluminum involves many challenges. The metal cast is not usually 100% aluminum. Pure aluminum is soft and not easily removed from the die cast tool due to sticking. Therefore, aluminum is alloyed with other materials such as zinc or silicone to make a metal having physical properties more favorable for fabrication and use. Generally in these alloys, only the aluminum oxidizes, leaving a finish that looks like it has a bunch of surface defects. Therefore, the entire surface of the waffle pans were given a nonstick coating rather than being anodized. As the last photo shows, the surface finish holds up well to cooking and will continue to due so with proper care. Pots and pans are formed using an entirely different method from casting. They are usually shaped from a single sheet of pure aluminum, which can be anodized as mentioned above. A lot of research goes into cookware design to ensure it is safe, durable, and manufacturable.