What does a Wort Correction Factor mean? Why is it set to a default of 1.040? Why/when do I need to change it? http://seanterrill.com/2012/01/06/refractometer-calculator/ Thanks.
It's an adjustment needed because wort is contains several types of sugars, not just the one simple sugar that refractometers are designed to measure. There's a little bit of discussion here... http://seanterrill.com/2010/06/11/refractometer-estimates-of-final-gravity/ I think Sean found that 1.04 resulted in the closest agrement with actual hydometer results for most typical worts. When you have a more fermentable than average wort, e.g. less maltotriose and more simple sugars. I believe Sean suggests using 1.02 for very fermentable worts.
Thanks for the reply, Vikeman. Can you quantify or put an OG threshold on "very fermentable" (e.g., 1.070 and above or something) or is it more so about the sources I am pulling my sugars from? And, just to be sure I am understanding you correctly, I will basically only be using 1.04 or 1.02 depending on my wort's fermentability, yes?
I believe by "very fermentable" he is talking about mash temps and adjuncts. If you mash at 147 and add 1.5# of table sugar to a Belgian beer or double IPA that is a very fermentable wort (much lower FG). If you mash at 156 and use dextrin malt along with lots of crystal in a Barley Wine or RIS that is a much less fermentable wort (higher FG).
I can't quantify it, but I can qualify it. Fermentability isn't related to the OG. It's just a result of the relative proportions of simple sugars to higher sugars. Jbakajust1 explained it well. Well, I think that's the way Sean thinks about it. But the phenomenon is not binary. I think if you really paid close attention over time to your refractometer results vs. hydrometer results, you'd find that there would be a continuous range of corrections to use, to go along with infinite possible wort fermentabilities. Personally, I use 1.04 for most worts, and 1.02 for worts that get a significant portion of sugars from something other than the mash, like table sugar, corn sugar, honey, candi syrup, etc.
