Second heat purge (for iso quickwash)

So before anyone starts filling this up with posts about bho. This is about isopropyl quickwash method. So after I scrape out the concentrate, after giving it a long steam bath with the 2 lasagna dish method, I place it in parchment paper and use my roztek equinox(hair straightener looking personal rosin press) to make it flat and thin to the circumference on the heat plate on the roztek so I can then purge out the rest of the alcohol. It bubbles great at 195°f. First it'll muffin really good and after letting it purge for an hour or 2 I flatten another paper on it, flatten it and transfer the reflaattened concentrate to the other paper and do it again. In a video it said that you keep doing this until the bubbles stop. Well after hours of purging it on the roztek it still has little bubbles in it and I can never get them to completely go away. Even If I have it sitting on 250°f for hours it doesn't make them stop and after too long on that high of heat it makes the end concentrate very runny and hard to handle unless you put it in the fridge/freezer. Also I believe it's actually killing my potency. So my question finally is how do i know all the alcohol is out? and if there's something I'm missing please tell me. I want the most I can get out of my product and I want it clean as possible.