Tip ... Iodine test

Brewing processes and methods. How to brew using extract, partial or all-grain. Tips and tricks.

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Tip ... Iodine test

Postby Azorean Brewer » Sat Feb 02, 2002 2:01 pm

For anyone out there into all grain or anyone thinking about taking the leap, here is a cool little test you can do to check if your mash has been completely converted. After the mash has gone through your normal schedule and you what to check to make sure that the grain has been fully converted, place a drop or two of tinture of iodine (available cheap at any drug store) onto a white plate and place a tablespoon of mash liquid next to the iodine, then just run the mash water into the iodine, if it turns black or purple you have a ways to go, if it stays orange you are fully converted and ready to sparge. Be careful with that iodine though you don't want to get any of it in your mash.

Paul.
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Iodine test results

Postby andytv » Sat Feb 02, 2002 4:12 pm

My club has about 200gal of all-grain batches under our belt, but has had some trouble interrpeting the results of this test.
For the most part, we rest single temp infusion batches for 90min @150F, which should be enough for an efficient conversion, yet sometimes the iodine still turns "dark brown". Regardless, all of our beers have been outstanding. Can anyone present this test in a more technical, quantifiable context?? What degree of color change is acceptable, etc??
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Iodine Test

Postby BillyBock » Sun Feb 03, 2002 3:28 am

Although not scientific, this test has usually given me good results. If I'm having trouble judging the color of the change, then I'll take another sample of wort and taste it. If it's malty sweet, it's been converting 60-90 minutes, and I've had a fairly stable mash temp., then I'll assume it's been converted and continue with my day. As far as color change, I only concern myself if it changes to black. If the color of the wort or iodine stays the same when added then assume conversion; however, supplement it with the taste test. If you have a dark wort, don't make your sample puddle too deep, that way the color won't be as dark and you'll be able to see the color change easier. Hope it helps.
--Cheers!
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Test Results ? ? ?

Postby Azorean Brewer » Sun Feb 03, 2002 6:46 am

Andy, Billy is right when you sit down and try to help you inevitably forget something. I mashed the last batch I made at 90 mins, and it still rendered black on the test, I sipped a little liquid off of the top and it still tasted starchy, kind of like raw bread dough. I let it sit for another 30 minutes, I went about my chores of cleaning and getting ready, at 2 hours the liquid tasted sweet and the test had little to no color change. Although homebrewing is more intuition than scientific I rely on what works more than anything. If you get black color after 90 min. wait and check it again in 15 minutes, chances are that you are right on the cusp and only a hair away from being fully converted. Also Billy was right in the amount of liquid, testing a pils is going to be a heck of a lot easier to check versus a porter or stout. Good luck.
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