My wife was making cheese sandwiches for the children’s lunches when I commented that they would like it better if she toasted the bread. She took the American cheese slices off the bread and put it in the toaster (the pop down kind) to toast. When I commented to her that I had been keeping the toaster parve she said that there was no trace of the cheese on the bread. Would I still be able to use this toaster to toast bread for a fleishig sandwich?
You can rely on your wife that there was no cheese left on the bread and therefore the toaster remains parve. Never the less if possible before using it for a fleishic sandwhich use it for a parve or milchic sandwhich so it can kasher itself.
Y:D 91:1 Shach 1, ibid Chidushey R. A. Eiger, ibid Pischey Teshuvah 1.