Labels Can Lie.

[Paul B. 523]

Don't you just hate it when a solution tells you one thing, but the results are totally opposite.

The concrete cleaner we used on a job states on the label that it will not darken or discolor concrete.

Closer look at the MSDS reveals that the key ingredient is Sodium Hydroxide - which can and will darken concrete.

Nothing a bit of Oxalic acid won't reverse, but I hate seeing misleading information on a label. Knowing how chemicals react with substrates can save you a lot of headaches.

[Jon 533]

Hmm, so you did not do a test spot?

Should have done the whole job like the darker area!

Hey if the oxalic does lighten it post a picture so we can see, I have never had good luck with oxalic.

Jon

[Paul B. 523]

Didn't need the chemical, it would have been a waste of money. Surface cleaner and water (some pool shock to remove leaf stains). This was a test and if the oxalic would not have worked, we would have made it all dark. The oxalic was Envirospecs White-Ox concrete blend for rust removal.

Sorry, don't have any after photos - it all blended - just have to take my word for it. We applied White-Ox, dwell 5 minutes, then rinsed. 15 minutes later we were applying V-Seal 101. Within an hour everything was dry.

I know the customer was happy since we were paid and picked up deck work from him.

I only took the photo to harass the chemical supplier (that's why I don't have after shots).