How bad is distilling before fermentation is done

What Happens If you proceed with distilling before fermentation is done?

The sugar and yeast remaining in suspension after flocculation in the wash can get burned during the boil-up phase and create off flavours. In a reflux still even though after refluxing you still get a strange taste that is not removed after using a filter. The amount of variables that are there due to an incomplete fermentation is crazy.

There will be free yeast and CO2 in the wash due to incomplete fermentation and degassing which will affect the distilling in a number of ways.

Temperature is unstable when distilling land leading to surging and fluctuation of the purity on the distillate during the distillation phase.

During the boil-up phase you can get foaming and puking of the wash caused by the C02 not being removed at the final step.

To de-gas your wash before and after fermentation is completed are very important steps  as they are linked. Removing the C02 from the wash is a simple step.

Your conversion will be affected, where you have planned for X amount of bottles of alcohol from the hearts section you will get a lot less due to the larger than normal foreshots and tails section. 

You can’t judge the final step of fermentation by tasting the wash. The wash at this stage will be taste slightly bitter. The only way how you can determine the final step is by using a hydrometer that will show you that all the sugar has been converted to alcohol (FG) and you have a stable FG.

The one mistake that newbies will make is by looking at the sugar wash batch surface and seeing C02 bubbles rising, thinking that the fermentation is still happening yet with no C02 escaping from the airlock. Full conversion is when the yeast has reacted with all sugar to make alcohol. C02 is a by-product 

This FG test should be done over two / three days. The first day you get an FG of say .092 and the second day you get the same result that you record as your FG.

If the result is not stable close up the fermenter and allow it to ferment for a few more days. This step is repeated till you get a stable result. 

One thing you must understand in fermentation is that it is the yeast through conversion that determines the quality and quantity of alcohol made. What does this tell you is that is you bypass this step you will also have unconverted yeast, and sugar that goes to the boil-up phase. Bad news.