In case the Colkegan in your cabinet is on the older side, and you recently looked at it to find that it was a bit hazy, have no fear, your whiskey is perfectly good. This condition occurred to one of our customers recently, and he dropped us a line to find out what was up. We turned to Stephen, our distiller extraordinaire, for an explanation. If you want to nerd out and learn about flocculation read all about it here.
The story was, they opened a bottle, drank half, left it for a few years (who does that?) and came back to find haze or sediment in it. This is a perfect time to learn a bit about why this might happen and if it is safe.
First: Yes, it is fine. We have a filtration process that removes large particles from the spirit, like char, bugs and whatever might have snuck into the barrel, tank etc. We filter the whiskey to 5 microns; we do not chill filter (more on that in a sec). 1 micron is one millionth of a meter. A human hair width is 90 microns. This is very small, but don't forget we are a craft distillery. We make a better, higher quality spirit than the big boys. We have more flavor, better cuts, better whiskey. At 5 microns, oils will pass through our filters. This oil for the most part is our flavor, texture and palate weight, our smoky tones, it is what makes our whiskey great. What can happen, especially over a long period and in the cold season, is called flocculation. This is basically the oils beginning to bind together in long chains or groups. This usually will fall to the bottle of the bottle and cause haze or small chunks to float around. There is no worry here, a quick shake of the whiskey or warming it will make these break up. But it might happen, and a consumer might be worried. They need not be; a quick education about it should 'clear' up the problem. Our spirit is clean, it is high proof, so nothing should grow or live in it. However, this consumer's bottle was opened, so we can never be sure if it was adulterated.
The big boys do something called chill filtering. Cooling the spirit down causes these oils to bind and solidify (flocculation). When filtered, they will be more easily caught by the filters creating a clearer, sparkly clean spirit. This looks great on a shelf, but actually can make for less flavorful, less complex whiskey. I personally find a bit of pride if we have some 'floc' (as we call it in the industry), as it means we have good oils and good flavor.