Damn iodine tests

[flight69er]

Can anyone tell me why i'm not getting a negative test for starch even after a 2hr mash? I use a cleans tablespoon and clean white plate, I'm mashing 4.5kg of grain at 67c with a protein rest at 55c.

[Jim]

Make sure there are no grains in the test sample. If you just test the liquid, you should get a negative test after less than an hour.

Plus it's not always easy to tell the difference, as the wort darkens as soon as you add the iodine even for a negative test. To get an idea of the true colour of a positive test, cut a potato in half and stick some iodine on the white flesh.

[farleyman]

Regardless of how your iodine tests are turning out
how is your beer turning out?

I used to see parts of grains still full of white starch in them after mashing.
I then set my mill for a finer crush, mindful that this could lead to a stuck mash.
Well, it has`nt happened yet. Sparging has not been a problem and my brew house
efficiency has shot up.
I know mills are expensive but this is still a reasonably priced hobby.
I no longer bother with Iodine testing. Try overnight mashing for good conversion.

Cheers farleyman

[Aleman]

There is a good article on the Iodine test in the march 2009 issue of Brewers Contact . . . It basically sounds as though you have some solids in the testing liquor . . . ideally you need just the liquid

[flight69er]

I find it quite difficult to get a sample without any pieces of grain in it. I must be getting a good conversion as my brews are about 80 to 85% efficient. Anyway thanks for the help lads.