Wednesday is my friend

Hello.
There is a ghost in my studio. For the past few months, the door to my studio has been slamming shut for no reason at all. There is no wind and the hinges on the door are not as freely moving as you would expect. In another words, it takes quite a bit of force to close the door. Yet it still slams shut with quite a force.
Having said all this, I have to be the most cynical and unbelieving person on this earth. I have tried putting up pieces of sail cloth to see if there was a gust of wind (which would be extremely unusual in itself as my studio has no windows). The other weird thing is that it usually slams shut at around 2pm everyday, not all the time but most days. Seeing this is a photographic studio that I work in, I should set up the camera with a motion sensor and photograph the door slamming, though I would probably need to do this with infra red or ultraviolet to pick up any unexplained things.
If I capture anything I will post it on this site. Till then I will be as skeptical as ever and blame it on....something.