I belive the definition is, to my understanding, is when a concentrate is ~90% melt when it comes to hash and dry sift. They have like a 6 star rating (now even 7 some places) and in most cases 5 star and above is considered full melt. But every place is different so hard to say really. Way I see it, if the bitch melts and nothing is left, then the bitch is full melt
To make dry sift full melt is pretty damn hard in most cases. There are new techs and tricks now a days to make full melt dry sift. There is the DrySiftWizard (DSW) tek which uses 2 screens that he sells, do a quick 10 second sift, and tada full melt dab on the bottom. Then theres the parchment paper tek, where you take a dvd insert and put parchment paper around it and "card" it. The best advice I can give, is go on YouTube and check out Bubblemans World, he has a lottt of How To vids and such. Or even try "parchment paper dry sift" and I'm sure you will get good results. Hope this helps and if it didn't well then damn you for wasting my time