I’ve seen people use knives on glass cutting boards and granite countertops (directly). They quickly became… not knives? Pieces of pointed sheet metal?
I don’t know, what do you call a previously perfectly fine knife which now is unable to perform any knife like action?
For some reason my daughters love to use my decent knives to cut food on top of ceramic plates and they frequently get tomato crushing dull. I bought an overpriced sharpener that had excellent reviews (from actual knife sharpeners not just Amazon customer reviews) that I think may be a counterfeit from Amazon. I think I just need to learn to sharpen well with stones and hide my knives better.
A dull knife can still cut. I’ve run across ones so dull they couldn’t cut clear tape on packages. Literally just grabs the tape and it rips off . Like I used my finger.
