I'm using a so-called cantenna (antenna made of a used can) as an example.
Suppose there's no evidence that anyone has tried a cantenna but antennas of similar design, just made of other materials, are well known. That "similar design" is also not protected by patents at this moment. Then at some point I discover that prefabricated used cans and other similar used packaging materials can be used to easily craft an antenna (reproduce the well known design) and it's usable as an antenna (practical). So basically the invention formula is "an antenna produced from used packaging materials by transforming them in such and such ways".
This method is cool for crafting an improvised device for fun or when you need such device for some lab research ASAP. However this way of manufacturing is not appealing for commercial applications - if one decided to make money on producing antennas he would likely use stock materials, not used package.
Can an improvised device made of used packaging materials (such as cantenna)be patented?