I've got to go for one next Monday. Fortunately, they're only giving me an enema as preparation. Far better than the Gastrografin they gave me last time, when I had a CT Colonoscopy 3 or 4 years ago, and they found a small polyp. They want to take a (ahem) closer look, and probably remove it this time.
I'm really looking forward to the visit!
(For those of you who watch Mock the Week, this conundrum should be in the "if this is the answer, what is the question?" section.
Answer: 3 hours.
Question: After taking Gastrografin, how long does it take for toilet paper to turn into glass paper?)