Mixing oxalic acid with 1:1 syrup 

TheWhaletail13 it can last a couple of months if kept refrigerated. Make sure you label the jar clearly if storing it in your fridge.

One week if kept fresh at room temperature.

Susie Q, oxalic acid is not approved for use with honey supers on. It is also most effective when there is no brood present. We like formic acid (Mite Away Quick Strips, or Formic Pro) for cooler temperatures with honey supers present.

That could be. I don't know for sure. I've actually changed the method I mix it slightly and don't stir at all anymore.

Ryan, you can see the video where we apply the treatment here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-uMBKOS3pSvg.html

Varroa mite control.