I see, to be honest I have not checked how clean it actually is. It is visually transparent, as opposed to the used one, but you are probably correct.

What I do is just expose the dirty isopropanol to sun or UV in general - the resin will precipitate. Then just filter it out and you have clean isopropanol.

They look like air bubbles to me, but it is weird they only come out after the bath. Could be they were already inside, but only covered by a thin wall of resin.

I usually use Isopropanol for bath not Ethanol, so I am not sure how your resin reacts with that. The bath should also be rather short, like 1min or something.

A few things to try:

• If you are shaking your resin before print, then give it like 10 minutes after you pour it into the vat, so all bubbles come out and pop
• lower the print speed
• add wait times between the end of lowering the plate and light on
• try to hollow out the model if possible, so there is less printing volume