Iodine Test – Avoiding a False Positive
Posted: Wed Nov 16, 2011 1:24 am
Here is an interesting thing I learned about the iodine test for starch conversion in your mash...
So you don't have to read the rest of my story, I learned that it is best for the test wort sample to be clear, ie, post-vorlof with little or no bits of grain in it in order for the test to work properly.
If the wort you are testing has grain material in it, particularly if you are brewing with a wheat malt, then the prevalence of those grains in your sample could lead to a false positive reading.
Of course this is common knowledge to some (or most) since I read it in a 1999 article of BYO and then heard in on the BN.
I learned my lesson after mashing my Weizenbock. Each time I drew a sample after the first hour and it came back negative, I kept telling myself "Just a half-hour more." This continued on until I mashed for approximately 2.5 hours. During this time I was furiously searching the interwebs looking for answers, thinking that somehow I effed up my mash and didn't get proper conversion. In the end, I said fuck it and made a brief offering to the brewing gods (they live in a shrub out back where I sometimes pee after drinking during a brew session) and just went on with my sparge, lauter and boil.
The beer turned out fine, but since then I have started taking my sample using clear wort after vorlof.
You can read all about my brewing shenanigans on my new blog: buscherbrauhaus@blogspot.com
So you don't have to read the rest of my story, I learned that it is best for the test wort sample to be clear, ie, post-vorlof with little or no bits of grain in it in order for the test to work properly.
If the wort you are testing has grain material in it, particularly if you are brewing with a wheat malt, then the prevalence of those grains in your sample could lead to a false positive reading.
Of course this is common knowledge to some (or most) since I read it in a 1999 article of BYO and then heard in on the BN.
I learned my lesson after mashing my Weizenbock. Each time I drew a sample after the first hour and it came back negative, I kept telling myself "Just a half-hour more." This continued on until I mashed for approximately 2.5 hours. During this time I was furiously searching the interwebs looking for answers, thinking that somehow I effed up my mash and didn't get proper conversion. In the end, I said fuck it and made a brief offering to the brewing gods (they live in a shrub out back where I sometimes pee after drinking during a brew session) and just went on with my sparge, lauter and boil.
The beer turned out fine, but since then I have started taking my sample using clear wort after vorlof.
You can read all about my brewing shenanigans on my new blog: buscherbrauhaus@blogspot.com