Stuck Fermentation vs. Unfermentables

[pablitocopado]

Hi, I´m new to this forum and its been a pleasure to read all o you. Last sunday i did 5 gallons all grain APA, it turned out OG 1060. I did a 1 liter starter with dma and a stirplate with S04, and pour it to the oxiganated wort. Fermentation started quicky and vigorously but after the third day y just stopped at 1030 (measured with refractometer). I know its been only a few days and that airlock activity means nothing but gravity doesnt seem que get any lower than this. If its done then atenuattion really sucks, i should get a FG of around 1016. Here is my question, I think i mashed in a bit high (160F), is there any way to know how much of these residual sugars are due to stuck fermentation or unfermentable sugars that yeast simply can´t handle. 15 gravity points seem a lot for unfermentable sugars. Thanks a lot and sory for my english, Im from south America.

 

[Foosier]

Refractometer is not accurate without adjustments when alcohol is present. There are calculators available on-line which will provide adjusted readings. Otherwise, you should use a hydrometer to measure FG.

Also, if it was a strong ferment, it may be at FG.

 

[redllama]

Use this calculator from Brewers Friend for adjusting for post fermentation refractometer readings. Based on my estimations you should be down to around 1.012 which would make sense.

 

[pablitocopado]

Refractometer is not accurate without adjustments when alcohol is present. There are calculators available on-line which will provide adjusted readings. Otherwise, you should use a hydrometer to measure FG.

Also, if it was a strong ferment, it may be at FG.

You where right, cant believe I did not correct for alcohol. i have the atc OG/brix scale and always work with gravity instead of brix. I did a hydrometer reading and its around 1019 with only a few days in primary it should be fine. thanks a lot !!!

 

[kh54s10]

A stalled fermentation is one where the yeast stop fermenting for a variety of reasons, but there are still fermentable sugars present. Fermentation could be restarted by raising the temperature, swirling up the yeast cake or pitching more yeast or a combination.

A high FG caused by unfermentable sugars which the yeast will not be able to ferment any more. This can be recipe, bad choice of yeast or high mash temperatures.

Already discussed. Refractometer inaccuracy with alcohol present.

Depending on the recipe, 160 degrees might not be a bit high, but a lot high. A pale brew meant to be dry might be in the 148 -150 degree F range. A dark beer I usually limit to about 154 degrees F. 1.019 might be as low as it will go, and it might be a little sweeter than desired.