Most of the calculators that I've seen assume 80% of the sugars extracted. Your own process will get more or less. Some people get much closer to the 100% than you'd expect.

 

It varies depending on equipment, process, etc. Usually at a home brew level the variance can be from a low of 65% and a high of 95%, with most people getting 70-80%.

 

My question is regarding conversion efficiency, so I thought I would post it here rather than start a new thread.

I put 3 dabs of iodine on this plate last night, you can see two brownish areas on the left and one on the right. Is this what complete conversion looks like?

 

Here is the grain bill, mashed at 149, pH was 5.1

 

You might look around on the web for more how to's but from my understanding to get a proper test you need to get a thin clean small amount of wart on that white plate. All those grain chunks will always have starch of some sort in it. Then drop a few drops of iodine and you will immediately see a brown tint or not. Brown means starch still present. If you want to do this test with every batch, do yourself a favor and go to the local drugstore and get a small bottle of iodine tincture. It is clear so if any amount of starch is present it will turn black for lots of starch, Brown for some starch and dark yellowish for only a bit of starch. Different colored wort will affect visual check. I don't test every batch but if i am doing something different its just another way to double check. I'm sure there must be some examples on how to out there, I was given a lesson in how to several years ago by a very experienced brewer friend. That's where the tincture came from. This was discussed before on BF but I don't remember where or when. You can see the results immediately, no need to wait overnight.

 

I haven't done an iodine test in quite some time. My method consisted of pulling out a little spoonful of some 'clear' wort and dropped a couple of drops of iodine. Purple/blackish indicated conversion not complete. Amber or brown was complete. Results are pretty much instant. Not sure the way I did it was best or not, and there's also a lot of nay sayers out there who say the test is inaccurate. There are just as many who believe it works just fine...go figure.

 

This was discussed in may. Search forums for key word iodine.
I knew my memory was faltering but 2 weeks ago?crap

 

You can say there's no starch where your iodine is. It doesn't tell you that there's no starch left in the rest of the mash, but what you've got is a good enough result to not get bogged down by that question and move onto whether you've given the beta amylase enough time to do the job you want and whether it's time to finish up the mash.

I was doing iodine tests for a few batches recently and the purple was pretty obvious for me when I did it at the start of the mash to check what I was doing.

 

Thanks guys

 

I've only ever done one. it's good to get some info on what to do if needs be. I'm guessing this is something that would be important when using a lot of cereals in the mash.

 

Conversion test is pretty useful if you're mashing without recirculation. You have to sample the clear wort, and BTW, if it's really good and clear, you won't find any starch in it. Probably the best way to test is by running a little off the bottom of the mash rather than scooping out off the top. I use it mostly to ensure that I'm getting more conversion after a good stir. Since I'm recirculating, I just let it clear up after a stir and get a spoonful coming out of the sparge arm. The iodine you get from the drug store starts out light brown so if it just stays that way, there's no starch. If it turns darker, purple, black you know there's still starch in solution.

I find that since I always do a long mash and do a couple of steps in the temp, conversion is always done, with the exception of a lot of unmalted wheat or a ton of corn or rice. More useful to me is checking the gravity with my refractometer. I can tell how much conversion there is based on the amount of water in the mash and the gravity. It levels out at some point with the main conversion rest at 148 but I always see an increase in gravity after I raise temp to 158. Meaning that the dextrin-producing enzymes becoming more active at the higher temps found some starches that the other enzymes gave up on.

 

Great advice, thank you

 

And keep in mind: Modern malts can convert themselves in 15 minutes. If you're going the full 60, you're extremely unlikely to have unconverted starches.

 

I used to test conversion with iodine but after 60 minutes it was always done so I stopped wasting my time.