Solargraphy Exposure Times

Hello All,

Tried to figure this out before posting but couldn't seem to find anything. I recently came across some solargraphy image and really want to give it a shot. I was simply wondering, what is the shortest exposure time to get an image on the photo paper without developing? While doing my looking around, I've seen the famous 6 month shots but I've also seen one's that have only taken a day. That's quite a large range. I realize that the exposure time will have a lot to do with pinhole diameter, but I'm sure there has to be some kind of baseline exposure time? Any help would be great, thanks.