False Positives from Iodine Test?

[Saccharomycetaceae]

I've recently started brewing a lot of beers, implementing a decoction mash. I've been having trouble though getting the decoction to totally saccharify. I feel confident that the temperature is right for conversion (I've just been doing a single rest at around 150 F before boiling, figuring that bothering with a two-step saccharification would be negated during the 145F rest of the main mash, but if that's not true, please enlighten me) and I've also been careful to raise the temperature of the decoction from dough-in to starch conversion slowly, around 2-3 degrees/min.
What sorts of things could be giving me a false positive for starch? I feel like it must be a false positive, but it would make me feel a lot better if I get it to test negative.
The only thing I'm thinking it might be would be small bits of mash. Usually, the liquor I pull to test settles into a clear layer and murkier layer indicating particulate matter...does any and all grain particle yield a false positive?
Any advice is greatly appreciated.
Thanks!

 

[GilaMinumBeer]

How are you performing your test?

 

[Denny]

I advise people not to even bother with the iodine test because of situations like yours. If you mash for the right time at the right temp, you WILL have conversion.

 

[Saccharomycetaceae]

To answer your question Gila, a couple drops of mash liquor in a white mug with a couple drops of iodine.
Denny, thanks! I very well may eliminate the test in the future, it's caused lots of head scratching lately that probably wasn't necessary.

 

[samc]

I think new brewers should do the test and take care to get it right. One or two drops without any solid material and one/two drops of iodine, stir them together on a white plate. Couldn't be much simpler. After you've brewed for some time you realize it isn't needed as Denny says, but it imparts knowledge by doing instead of by other peoples experience. Priceless.

 

[Denny]

I always show a new brewer how to do the test, then tell them they'll never need to do it again.