DID YOU KNOW
There were several types of envelopes created for different uses. As they needed to be light enough to fly around the room, ten thousand single sheets of paper were printed with the envelopes graphics, including the Hogwarts seal on the back. There were also several letters that had a real wax stamp on the back so they could be seen in close-ups. These contained the actual letter sent by Professor Minerva McGonagall, handwritten by graphic artist Miraphora Mina, who wrote many other documents for the film series. The owls that brought the acceptance letter to number four, Privet Drive, did carry real envelopes, in a way. A plastic harness with a release mechanism and a long, undetectable cord that was held by a trainer was placed over the birds body. At the proper time, the trainer would open the release mechanism and the owl would drop the envelope.