If you choose to alter your air popper you are assume the risk that it will no longer work as it was designed to, that it might not work at all, that you might injure yourself in performing these tasks or in using the altered device. This information is here for you to peruse, but Sweet Maria's accepts NO responsibility in what the results may be. Cutting tin cans with snips is especially hazardous ...expect injury! Be Careful!
Creating an experimental top for your roaster from household trash can be fun and rewarding. Any changes you make in the hood on your air popper will change the roast because you are modifying the thermodynamics of the air flow. Here are some photographs and notes of a chimney I built that traps chaff very effectively. The roasts take slightly longer with this device installed. I tested it with a West Bend Poppery II, but it would work with any popper with minor changes.
The irony about this chimney design is that I don't think its a significant improvement over the standard popper hood. Chaff is no big deal, I think its smoke that concerns more poeple. Well ...this whole design was intended as a smoke reducer but I never got around to it. How would that happen? A lightweight automotive air filter would be added, encircling the lower part of the outer can, over the openings/mesh. I think that if you could find a cheap paper auto air filter that didn't restrict air flow too much, this design could really work. I'm just too busy right now to investigate the options ...
Please let me know if you have any ideas, innovations, or chimney building success stories. I'll be glad to post them here, or feature your invention in an article of its own.