SG rises before falling

[modernhistorian]

I've been making wines for about nine years, mostly kit wines but also country wines from Palisade peaches as well as mead. A couple of years ago, I bought a hydrometer that reports the specific gravity electronically, and noticed a strange (to me) phenomenon. After pitching the yeast, the SG would rise for up to 24 hours before beginning to fall. The temperature is held constant during this. For example, I started a Nebbiolo this week, and the SG rose from 1.091 to 1.099 over 22 hours before beginning to fall.

Is this a known process and, if so, what is the cause? Should I calculate my ABV from the first reading I take, or the highest? Thanks for any insight.

 

[BigDaveK]

I noticed that a couple times as well. I put it down to my fruit breaking down and affecting the density, not necessarily the sugar content. I haven't noticed it with my "tea" or juice musts.

 

[winemaker81]

With kits, there is a problem with getting them to mix well. I have been checking SG, reconstituting kits one day and inoculating the next. There is usually a difference in SG, regardless how well I stir.

With fruit, as Dave said, there is more breakdown, with sugar extraction.

 

[modernhistorian]

I see this with the grape wine kits as well as the fruit wines, even those with no added grape skins or oak chips, just juice.

 

[Jovimaple]

Welcome to WMT!

I have a couple of Tilt hydrometers and have found the same thing. I assume it's because the juice is homogenizing over time.

I decided for my purposes, it's the total change in SG that I want, to get an approximate ABV. This usually means I use the higher number. When I determine the ABV, I ignore the additional volume from the flavor pack or additional sugar if I backsweeten. As a home winemaker, I am looking for an approximate ABV and I don't really care if it is exact.

 

[winemaker81]

I see this with the grape wine kits as well as the fruit wines, even those with no added grape skins or oak chips, just juice.

Concentrates are typically around 68 brix, and resist mixing as they are thick, so we get pockets of varying density. The must is homogenizing overnight.

Since performing my check, I've improved my mixing process. I'm getting better results by adding concentrate to the bentonite water and stirring for 1 minute, changing direction half way through. Working with my son, we stir while adding water up to 23 liters.

For grapes, I'm crushing one day and inoculating the next. I check SG in 3 places in the fermenter, and if It get any differences, I stir the must, then check again.

 

[modernhistorian]

Thanks for the comments. I will use the highest SG to calculate my ABV. It is fermenting normally, and down to SG 1.009 today.

 

[QuiQuog]

I have no experience with these types of hydrometers, but as I understand it, the device tilts in relation to the density of the must. More tilt equals higher SG, less equals lower. At the start of fermentation, the bubbles are more numerous. Couldn't the rise in gravity be due to bubbles lifting the device and making more tilt? You get a similar effect with a standard hydrometer before you knock the bubbles off.

 

[modernhistorian]

I see the rise in SG before bubbles form. Also, bubbles lift the device around its center of gravity, so the tilt remains the same.

 

[KennethLamas]

Any solution?

 

[modernhistorian]

Consensus is that the must is homogenizing with the added water, so just wait for the SG to stabilize then use that as the baseline for ABV and pitch the yeast.