Author Topic: Will clear / decolorized iodine work for the starch / full conversion test?  (Read 1847 times)

Offline imperialstout

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Wondering if the clear, decolorized iodine will work for the starch / full conversion test. My guess is it will if it is the iodine that changes colour and not the colour added to the iodine that changes. My guess is if there is no starch left the clear iodine will stay clear, otherwise it will turn purple. Any thoughts?

Online mtnrockhopper

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Not sure, but there is no dye added to either. CVS lists the ingredients for both and Iodine tincture contains pure iodine and sodium iodine while decolorized iodine contains potassium iodine only. My guess is the answer is no since potassium iodine probably has different properties.
Jimmy K

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Offline denny

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Will clear / decolorized iodine work for the starch / full conversion test?
« Reply #2 on: February 04, 2013, 09:16:28 AM »
Truthfully, I suggest you just skip doing the test.  I know of too may people who get false readings from it and it really doesn't tell you if you have full conversion.
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Online mtnrockhopper

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Truthfully, I suggest you just skip doing the test.  I know of too may people who get false readings from it and it really doesn't tell you if you have full conversion.
I've heard that too.  I don't know anybody that still does iodine tests.
Jimmy K

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Offline tschmidlin

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I don't do iodine tests either and don't recommend them, but you could put a drop on a slice of bread and see if it changes color.  You'll have your answer.
Tom Schmidlin

Offline imperialstout

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Not sure, but there is no dye added to either. CVS lists the ingredients for both and Iodine tincture contains pure iodine and sodium iodine while decolorized iodine contains potassium iodine only. My guess is the answer is no since potassium iodine probably has different properties.

My brother always said searching for information is like panning for gold, most of the time you just get a few bits but once in awhile you get you get a nugget that make all the effort worthwhile. This was definitely a nugget. Decolorized iodine is a misnomer, it is not iodine that has had the color removed, it is in fact potassium iodine, a different compound. What brewers want is iodine tincture containing 2% pure iodine and 2.4% sodium iodine in a 47% alcohol solution, the remainder being water. Don't know if doing an iodine test is worth it but as someone else said, it is another tool to use to help you make the best beer you can.

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I was writing that wondering how different they could be. Then I remembered - chlorine can kill you, sodium will basically explode if thrown in water, but together ... quite tasty.
Jimmy K

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Offline CASK1

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Braukaiser has some really nice scientific info on the iodine starch test here:

http://braukaiser.com/wiki/index.php?title=Iodine_Test

Offline imperialstout

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Thank you CASK1. That article is everything anyone needs to do an iodine test correctly, and why. Had been using clear iodine, a different compound than the red stuff, at mash temps. Now know to use 1 part regular iodine, mixed with 9 parts rubbing alcohol and do the test at room temp.

Offline euge

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And by now should be eschewing the use of this test: it is a waste of time. Malt wants to convert. If you have a conversion problem then we need to investigate that instead.
The first principle is that you must not fool yourself, and you are the easiest person to fool. -Richard P. Feynman