There is a whole thread on this I believe in the hash forum. IMO, I believe that the most important thing when making water hash, especially if looking for pure bubble is the quality of the trim. You probably already know that, well from my experience to get the purest bubble I would use trim that has been dried for only a couple of days. Still super fresh, just not right off the plant. I have tried everything lately, freshly off the plant, super dried, and a couple of days dried. While all of it is capable of making full melt, the biggest amount and the highest quality seems to come from the couple days, I have no scientific reasoning other than my own tests. I do let it all get super cold, the weather around where i live has been below zero lately, so I was able to just make all the bubble outside, that helped too. I also love to get the bubble as dry as possible when making it (squeeze all the water out of the bag, every drip) then I like to cut it up and let it form into a powder. This is like kief times ten. If it is good then it will still form into a ball or whatever at any time, but can also be more convenient and better when I let it dry like this, as opposed to pressing it wet as some do.