I just sent this note to the Tilt folks. If anyone here has any insight I would welcome the comments:
“I have a circumstance that is confusing me (which is not all that difficult):
As I have been doing lately, I made a fermentation addition three days after the beginning of fermentation. To do that I unlatched the four latches on my BrewBucket, remove the lid and replace it once complete.
After making the addition, on the Tilt I began to notice the SG lower than I’ve seen it in the past — in the .9xx range.
As I was pouring a beer last night, I decided to take a peek into the fermenter fridge to see some air lock bubbles. There weren’t any which I thought was odd at this stage of fermentation. It seems this time after making my addition, I inadvertently did not relatch the lid so CO2 was escaping around the lid seal.
Within a few minutes after relatching the lid I noticed the Tilt had begun reading what I have been accustomed to seeing at this stage — in the 1.01x range.
I say all that to ask this: what was I seeing? Does pressure inside the FV affect the Tilt SG?”
I think that in principle a high pressure could change a Tilt reading, but I doubt that the tiny pressure difference in your case would matter. I haven’t used a Tilt, but I have built a home-made item that does the same thing and noticed that sometimes it would float to the edge of the fermenter and the top of the hydrometer would get stuck in gooey krausen residue there, which caused bogus readings. A bit of jiggling would break the top free from the sticky fermenter wall and it would read properly again. Perhaps that is what happened to you. When re-fastening the lid you might have unstuck the Tilt.
I think Richard is probably right, although on one fermentation a few weeks back, I had a similar low Tilt reading throughout fermentation. I had put the Tilt in and racked chilled wort on top of it and a good slurry of harvested yeast; long story short - the Tilt somehow got stuck under the Brewbucket’s dip tube, which was in the downward curved position, so it held the Tilt for the full time of the fermentation. I just assumed that it was a battery going dead or something, so I didn’t figure it out until I racked it (closed transfer) and then opened the lid to find it lodged under the dip tube in an unusual way and figuring out that it just wasn’t free floating. Strange things can certainly happen, but usually, they are nothing to worry about! Even so, they can be temporarily confounding.