I have open fermented 3 different beers so far. Belgian Patersbier with Wyeast 3787 Trappist, a Belgian Quadrupel with Wyeast 3787 and a West Coast Amber IPA with Wyeast 1099 Whitbread.
For the Quadrupel I chilled down the 1.080 wort, left it overnight from midnight to 10am then pitched the Trappist yeast in a 2 liter starter at 68 degrees before I left for work. I came back 10 hours later to find a thick 3 inch krausen. By day 2 my gravity had dropped to 1.043 and I had a 6 inch foamy krausen head that was slowly growing and overflowing out of the bucket. I forgot where I read this at (possibly the Wyeast website?) but if your krausen level gets too thick on the 3787 yeast it is recommended that you swirl your fermentation vessel around to break it up a little and relieve some of the pressure that the thick cap of yeast is holding.
All in all I had the fermentation open for 5 days mainly because I knew the Trappist yeast was going to make a huge mess in a standard glass carboy. Also Adam Avery mentioned having a strong pitch of 3787 for this so I figured a consistent supply of oxygen would help build up extra yeast. There was a point where the krausen level dropped back down to 2 inches and I thought it was safe to put the lid back on... turns out I was wrong. In the middle of the night the lid burst off and flung trappist yeast all over the walls and onto my bed where I happened to be sleeping. Talk about a rude awakening.
Once the krausen level was getting low, 2 inches give or take, I decided it was time to cover it up so I didn't get any further oxygen into my beer. After about 5 days I was down to 1.018 and still actively fermenting. A few days later I decided to move it to a sanitized carboy. I sampled some and it tasted very "Belgian-y" and raisiny but it was hard to detect to true flavor because there was a ton of yeast still in suspension.
Hope this info helps. Let me know if you have questions. If you decide to do this, whatever room you do it in will be overcome by the aromas of fermentation. Oh and I will say I didn't skimp on the cleaning or the sanitizing of anything before I used it. I treated the fermentation the same as I would for a normal closed fermentation.
Here are a few from the Belgian Quadrupel that I hope comes close to Avery's "The Reverend".IMG_3242
, on FlickrIMG_3255
, on FlickrIMG_3247
, on Flickr