The Life Hack Stack Exchange has an answer talking about a prototype "toastie knife" from Warbutons Bakery.

It was claimed that the prototype knife would heat up to allow butter to be spread more easily.

The knife was also reported on by the UK Daily Mail, amongst other places.

The We Love Ad site talks about the success of this marketing campaign, describing this as

a one-off branded prototype butter knife with heated, battery-powered element operating at 48ºC, the optimum temperature to soften butter - and launched it via traditional and social media, with supporting infographic, YouTube video and ‘#toastieknife’ hashtag.

The advert brags about achieving an optimal butter spreading, at a temperature of 41.8°C in 30 seconds, using two AA batteries.

I'd be interested to know if a working prototype was ever produced.

  • I don't see a problem with heating a knife to 41.8°C with batteries. That's only about 20 degrees above room temperature, and the specific heat of stainless steel is very low (i.e. it takes very little energy to heat it.) – Moyli May 1 '16 at 12:30
  • @Moyli It's only using two AA batteries and it's supposed to be melting enough butter to help you spread it. Sounds perfectly reasonable to you? – candied_orange May 1 '16 at 13:13
  • It seems no-one ever said that the knife was in production - it seems clear it was never the intention to go it into production. So, I have focussed the question on the claim made; that a prototype was produced. The trouble is I can't even see where they claim it was a working prototype. Mocking up a plastic model of what it might look like if it worked still is a legitimate prototype. – Oddthinking May 1 '16 at 15:01
  • @Oddthinking I can understand why you want the question focused. I had intended the four points to be used in an exclusionary way, not as a buffet that you could pick from and only address one. If you think this is the only way to make the question viable I'll accept it. – candied_orange May 1 '16 at 15:45
  • Doubt that it would actually work. Put a cold piece of butter on toast and try to spread it with a warm knife. The knife just slips over the surface of the butter. So can one produce a "working prototype" of something that won't actually work? – jamesqf May 1 '16 at 17:32

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