I think we’re only talking a couple of teaspoons full. Not enough to matter in my opinion. None of the kegs is exactly the same volume.
Okay. I’m waiting for your report on the color of the sample you pull. That will be the first concrete evidence on this question.
This whole thing finally motivated me. Just ordered test strips. 
EDIT Jeffy, if you’re interested, search “iodine test strips” on Amazon. Bunch of choices, all ~$8 for 100 strips.
I apologize for not providing a clear answer to the original post on this thread.
Your method will work just fine, and will achieve the desired outcomes of clean and sanitized kegs in an efficient manner. The fact that the kegs are pressurized, in the dark, and clean of organic material will ensure that the BTF Iodophor solution is viable for the job. As long as the kegs you sanitize and purge in this fashion remain pressure rated, they will stay in a sanitized state until use. Exposure to outside air through a. Leak would compromise this.
I would welcome your input regarding a test of the solution in storage with a test paper at the end of the process, but if kept pressurized and sealed, in the dark, I would imagine this solution would be viable for quite a while - it’s just difficult to give you an exact length of time.
In addition, small amounts of properly measured, 12.5 PPM BTF Iodophor, such as barely a tablespoon, will dilute out into such extremely small concentrations in your finished beer that it will be undetectable. I refer again to the PDF I linked in an earlier post for a good experiment:
I sincerely hope this helps and please contact me if there are unanswered questions.
There is a good reason for indicating air drying. Since the initial application of BTF Iodophor was a third sink sanitizer for sanitizing bar glassware, food code and sanitary guidelines need to apply for standard three compartment sink ware washing. Here is a document from the ServSafe safe food handling program:
https://www.servsafe.com/ServSafe/media/ServSafe/Documents/poster_12.pdf
Dishes, utensils, glasses, etc. that are sanitized in a third sink must be air dried (not towel dried), inverted on a rack before using again or before storage. The instructions on BTF Iodophor to air dry before use reinforce the application of the product as a bar and restaurant third sink sanitizer.
For the use of BTF Iodophor as a sanitizer for home brewing, I don’t feel it is required to completely air dry equipment for brewing, such as kegs or carboys, etc. Shaking off or draining out as much of the end use solution as possible will suffice. See the quote from Dr. Landman in the article I linked earlier:
“”NO RINSE” is a phrase that is frequently used in conjunction with iodophor. Manufacturers of Iodophor claim that, when used in a solution of 12.5 ppm, there is no need to rinse to solution from items. They say that the item should be merely air dried. Dr. Landman opined that air drying wasn’t really necessary.”
That makes sense. Star San, Sani Clean, Io Star - they all say the same thing regarding air drying. Always wondered why and it makes sense that we wouldn’t want them towel dried. Easy to forget that the solutions weren’t made specifically for my home brewing [emoji2]
I tapped a sample tonight from a corny keg marked “iodophor 1/12/19, transferred to this keg 2/17/19.”
The color is pale yellow if not lighter. Almost no color.
I will see if my local store has test strips this weekend, but the color tells me that it’s not a viable solution.
Interesting. Sounds like there’s a very small amount of Iodophor still present, but you will need to verify the concentration with a test strip to be sure. I’ll be interested to see how this tests out when you can measure.
I recently listened to a Master Brewers Association podcast episode titled “Efficacy of sanitizers in the brewery” in which a Brewer from Bell’s discussed an experiment they conducted on kill rates of sanitizers after switching from ethanol to iodophor for spot spraying valves, etc.
Long story short, after the experiment they switched back to ethanol. Lots of great info there. It’s worth a listen.
We had a lengthy discussion here about that when it came out.
https://www.homebrewersassociation.org/forum/index.php?topic=32077.0
Long story short, that study’s methodology was so fundamentally flawed that it couldn’t pass muster in a grade school science fair. That it got as far as a poster presentation at MBAA is a warning to regard with suspicion anything they promulgate. Iodophor is a stone killer, no question.
Damn you, Internet!
I just tested some with the strips I got (same brand hopfenundmalz posted about above.) 12.5 ppm is a WAY lighter, yellowish, color than what I expected. You might be ok, but you’ll have to test to find out. It will be good to recalibrate my eyeballing of the color. I’ve probably been wasting concentrate because I thought it looked too weak.
I picked up some test strips today and checked the solution in the above keg. It was pretty much no color change on the strip. I then tested a solution I had made up this morning to sanitize bottles and equipment and it looks like it reads about 12.5 ppm. Interestingly, if I look at the latter in the tub (about 7 inches deep) it is mid amber in color, but in a typical judging cup, the liquid is almost colorless. So if you are going to use color of the liquid as an indication, you need a deep enough sample.
I think I will experiment a bit with kegs and age to see how that progresses.