Gravity of the suar-water mixture increased just after pitched the yeast.

[epikuryan]

Hello Brewers,
Yesterday night, I started an experiment of tracking gravity and temperature with an iSpindel implementation.
The thing is, as you can see from the below chart, the gravity has been increased to 1.070 from 1.055 in 4 hours, and it dropped back to OG value again in 10 hours.

Now the gravity inclined to drop as expected.

I am not able to justify why there had been an increase in gravity at the early stages of fermentation. I do not expect it to be because of wrong interpretation of the sensor signals.

More details:

• The fermenting liquid is mixture of sugar and water. The yeast is regular baking yeast
• The fermantation container is an open bucket
• There is some Krausen formed but it is not in contact with the iSpindel
• As can be seen the temperature is quite constant
• There is no mechanical impact/strike to fermentation bucket and it is sitting on a flat place.
• Bucket is wide enough and water level is high enough so that the iSpindle is not affected by the walls or bottom of the bucket

My initial theory is that, since the yeast is top-fermenting yeast, it first changes the density of the surface ( but even in this case, the high gravity liquid should go to bottom since it is heavier).

Any ideas about the case? May it be a chemical reaction that is causing the reading to be high?

For the ones who did not hear iSpindel, it is a cyllinder tube submerged in the fermenting beer and depending on the tube's angle, it measures the gravity of the beer. And I can say that in my previous experiments where I compare the iSpindel results with hydrometer readings, the reading sensitivity is good.

View media item 69005

 

[fizzix]

I'm guessing that the top-lying bakers yeast action is temporarily buoying the iSpindel --tilting it just enough for an increased reading. The yeast eventually migrates down and returns the iSpindel to its initial tilt. If it consistently does this throughout future recipes, it just may be the nature of the beast and you can ignore the temporary off-readings.

(Quite a neat device, that iSpindel!)

 

[ajdelange]

I think fizzix is probably right with the action he mentions being the accumulation of CO2 bubbles on the bottom part of the cylinder. The same thing happens with a hydrometer if a sample isn't degassed. It would seem this would be a problem with the intended use of the product which, as I understand it, is intended to float in the beer and relay tilt angle via Blue Tooth.

 

[epikuryan]

I think fizzix is probably right with the action he mentions being the accumulation of CO2 bubbles on the bottom part of the cylinder. The same thing happens with a hydrometer if a sample isn't degassed. It would seem this would be a problem with the intended use of the product which, as I understand it, is intended to float in the beer and relay tilt angle via Blue Tooth.

Actually I do not suspect of bubbles. There was not much bubbles even when the gravitiy reading reached the top. And if bubbles cause a lifting effect, the effect should be applying nearly same to whole tube and the angle (which is mapped to gravity in the working principle) will not change too much.

 

[Smellyglove]

But it's 100% an error from the ispindel. Gravity does not rise after dumping yeast into a solution. Maybe yeast clinged to the ispindel due to positive/negative charge, or other means, and made it shift the tilt.

 

[ajdelange]

The lifting is not applied to the whole length of the cylinder but only to the part that is submerged. Thus the effect of adhering gas bubbles is the same as increased density of the fluid: increased buoyancy. The thing will tilt more.

That is not to say that adhering bubbles is the cause of what you are seeing. It's just a reasonable guess. Easy enough to check though. Repeat the experiment and when the apparent gravity is approaching its peak remove the device and degass the fermenting mixture. Then replace the unit and watch what happens. At first the reading may be low but eventually, if the thesis is correct, gas bubbles will again accumulate and the reading rise.