E-6 cleaning JOBO bottles

So I am firing up the JOBO CPA2 in preparation to get the students doing some E6 pretty soon. I have a slew of bottles and am thinking of keeping the chemistry the same as they were the last time they were used (about a year ago).

I want to clean them out though of all the gunk that may or may not still be in there. Other than rinsing with HOT water, does anyone have any suggestions on how to clean these things?

Thanks!

not without the right PPE

I use warm/hot water, and about 10mL of concentrated sulfuric acid.

Wear a lab coat, aprion, etc and nitrile gloves, splash shield for face.

Hold cap on loosely to clean the threads and cap edges as well. Do over a sink, then rinse throughly.

Gets rid of all the brown cruddies stuck to the bottom of containers.

Thanks man! I do have some crusties.