Blue distillate - and how to correct it

First published on Distillique's website in 2015 by GM Bosman

If ever you distil your mash and find that you get a blue-ish colour (and perhaps even a copper/metallic taste) don't drink it!

It is not fit for human consumption. 

When distilling "faulty" mashes the distillate will start off with a bluish colour and slowly the blue-ishness will turn less blue as you continue to distil. These faulty mashes is the result of chemical reaction between the copper of your still and ammonia. 

To explain:

Nitrogen is used in many nutrients to allow the yeast to grow and ferment healthy. However, too much unconsumed nutrients can also create a problem during distilling.  

The nitrogen (from the nutrients) reacts in an alkaline environment to form ammonia. The more residual nitrogen and the more alkaline (or less acidic) the mash, the more ammonia results. This ammonia then corrodes the copper and results in a "blue-ish distillate which tastes not good at all. 

"Blue-ish" distillate should be discarded and is not fit for human consumption. 

To prevent this: Use less nitrogen containing nutrients and ensure the pash pH is acidic rather than alkaline  - easy as that!

If you do expect the mash to contain residual nitrogen just before distillation, make sure to keep the pH low (acidic) before distillation. An alkaline mash makes the nitrogen/ammonia/copper problem even worse. Ideally your mash's pH should be between 4 and 5.5 (use pH test strips to confirm this).

After a blue run, just flush all copper with clean water and it will be fine again