Now, his trusty lemon — 110 years old and shriveled black — will be on display starting ... “Lemon juice had been used for centuries as a form of ‘invisible ink,’ since it cannot be seen on paper ...

Now, his trusty lemon - 110 years old and shriveled black - will be on display ... for centuries as a form of ‘invisible ink,’ since it cannot be seen on paper until it carbonizes when heated ...