Iodine Test?

[mahrsbrau]

I've been looking into to my homebrew books and I keep seeing suggestions about using an iodine test for mashing. It's supposed to let you know if the mash is ready for sparging from my understanding. Does anyone actually use this? Or is the hydrometer my best bet?

[BDawg]

Iodine is really useful because it changes color in the presence of starch. You might have done this experiment back in Jr. High where you put a drop of iodine on a slice of bread, a potato slice, etc, and watched it turn very dark purple/black as soon as it hits the surface.

Likewise, if you take a small sample of your mash wort (use a screen or filter to keep grain chunks out - I have a tea strainer I use to do that) and put it on a plain white ceramic dish. Then, a few drops of iodine will tell you if you have converted or not. If the drop of iodine stays amber, its done. If it turns black/purple, then you still have starch so let it keep mashing.

(Either way, iodine is poisonous so throw the sample away after testing).

This has saved my ass more than once, especially when I first got into all grain.
I had a mash that didn't convert for 2 hrs and finally figured out that it was a mash pH issue, but I wouldn't have known if I wasn't using the iodine test to check.

Good luck & HTH-

[mahrsbrau]

Awesome thanks bdawg ill definitely be using that then.

[Ozwald]

The drop or 2 of iodine would be too small an amount to be toxic if you did put it back in, but as a general rule any sample you pull off for testing never goes back in. Doesn't matter if it's iodine, hydrometer, anything. Pull it, test it, record it, toss it. (I'm selling that one to Daft Punk)

[brewinhard]

Wise words from my brewing guru.

[Dirk McLargeHuge]

Pull it, test it, record it, toss it.

Is that a euphemism for something?

[Bad Goat Brewing]

So when the iodine test shows all the starches are converted, do you mash-out? What if it shows conversion 20 minutes in?

[Dirk McLargeHuge]

So when the iodine test shows all the starches are converted, do mash out then? What if it shows conversion 20 minutes in?

Sometimes conversion can happen in 20 minutes. If it does, then proceed.