Full melt is an informal quality description for hash that melts readily with very little solid residue under suitable conditions. It's commonly associated with carefully separated resin glands and the top of hash star-rating systems. It isn't a regulated laboratory grade.
The word is useful because hash doesn't all behave the same way when heated. It becomes misleading when a seller treats it as proof of a THC percentage, a farm's practices or freedom from contaminants.
A behavior, not a production method
Both bubble hash and refined dry sift can be described by how they melt. Bubble hash tells you how the material was separated; full melt is a claim about how the result behaves. One doesn't imply the other.
Lowtemp sets a stricter bar than the definition above. Its hash-format overview describes full melt bubble hash as hash that “melts completely and without leaving residue when dabbed,” and its bubble hash and rosin comparison places full melt at six stars, meaning “it melts completely when dabbed.”
This guide says “very little” instead because no shared test sits behind “completely.” The device, the temperature and the observer's idea of a trace all vary from one report to the next. A speck left behind isn't a standardized fail, and a clean-looking result isn't a standardized pass.
Why micron and color can't settle it
Lowtemp's overview associates full melt with trichome heads typically in the 90 to 120 µm range. A screen fraction can help describe a product, but it can't guarantee how a particular cultivar or batch will melt. The smallest screen isn't automatically the best, and a bigger resin head isn't automatically cleaner.
Pale color can be attractive without proving a grade. A photo of wet hash in a bag can't show how the dried product will perform. Ask the producer how the grade was assigned and whether it applies to this exact batch.
Full melt and six star
Six star is widely used for the top of the informal star scale and often paired with “full melt.” No independent body applies identical conditions to every commercial jar. The six-star guide covers that label, and the grading overview explains the rest of the scale.
So the context around a melt claim carries most of the information. A menu that says who graded the hash and on what basis has told you something that a row of stars hasn't. A review that names the batch and the setup is more useful than a single result treated as a verdict on an entire brand.
Melt doesn't replace testing
A melt claim isn't a contaminant result. California's testing program requires batch testing for things appearance can't establish, including residual pesticides, heavy metals, microbial impurities and foreign material. Check product and device instructions too, rather than assuming every grade of hash suits every chamber.
The comparison with rosin is a choice between related formats, not between a good and a bad version of the same thing.