Just an observation here. When I went to Sam's yesterday to buy bleach there was an open case of 3 bottles of Clorox "ultra" bleach - labels on the bottles said 6%. It was the only case labeled "ultra". I then looked at the labels on the bottles of Clorox regular bleach - same thing - 6%. If you go to their current website there is no mention of "ultra" - just new, improved with more whitening power. Because there was a big Internet "lye" going around when the ultra was introduced, I'm thinking they've removed the word "ultra" and all their regular bleach is now 6% - I couldn't find anything at their current website that specifically mentioned this to be a fact but there was no mention of ultra - you can "google" clorox ultra and get some hits but they mostly reference the "lies about the lye" and some older (2001) information about "ultra" from other websites. The following is their statement on what makes the new "regular" be an improved "whitening" formula -
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How has Clorox® Bleach improved its whitening formula?
We have a new patented formula across the entire line of Clorox® Bleach products. The new formula incorporates an ingredient, sodium polyacrylate, that binds to certian minerals that are in the water supply preventing them from depositing on your clothes. You get all the power and performance of Clorox Liquid Bleach you are used to, but now clothes will retain their whiteness that might have been lost over time due to deposition of these minerals.