The inside has been that way for at least 4 years
I bought this to clean our school's coffee air pots and it did a great job of getting the old coffee stain out, but I forgot to take a before and after picture.  I looked around the school and found a few other coffee pots that haven't been properly cleaned in years.<br /><br />The before picture has a least 4 years of coffee stain. The first pass left the remnants of a previous burn ring, so I refilled it and left it for 48 hours. The key to getting the best results is very hot water and let it sit for 2+ hours.<br />Afterwards, everything breaks down but you can help it along with a light scrubbing.<br /><br />After the first coffee pot miracle we bought a case!
Rating: 5 stars