Dry Ice Hash or Bubble Hash? What's the difference?

Dry Ice Hash

Generally, dry ice hash is less pure than bubble hash. This is because in addition to trichomes, you are likely to also have broken pistils (hairs) in your extract. Dry ice kief can also have pulverised plant matter in the mix. The best dry ice kief is usually made with the small 'popcorn' buds and sugar leaf trim. When more of the fan leaves are added the quality will degrade. Your plant matter should also still have some moisture content to it before you kief. Bone-dry plant matter will pulverise quickly and end up in your kief.

You can make dry ice hash from fresh frozen trim. This is good because the dry ice tends to break the trichomes free from the plant matter before it gets pulverized. The kief extracted with this method will still have moisture in it, but it can be pressed and smoked. This means that if you want to keep it from growing mold you will have to store it in the freezer, or you can let the kief dry for a few days or a week or so before pressing it.

Many hash smokers tend to like a pressed kief type of end-product because you don't need any specialized smoking aparatus. You can smoke it in a regular pipe. Dry ice kief can also be rosin pressed to squeeze the oils out of the waxy membrane that encapsulates them, for those that prefer to dab.

The dry ice method is a fast way to extract kief.

Green Candy dry ice hash from fresh frozen trim shown below.

Bubble Hash

The bubble hash method requires a little bit more work, but can yield a much cleaner product. When extracted in cold water, the trichomes tend to drop to the bottom of your bucket or washing machine while the plant matter tends to float. When the extract is classified through a series of decreasingly sized mesh filters, you can isolate the best parts of your extract. The bulbous part of the trichome, which contains the good stuff, will usually be somewhere between the 160 micron and 60 micron range. The best quality bubble hash, as far as the strains I am familiar with, usually end up in the 90 micron bowl (90um to 120um) and the 68 micron bowl (68um to 90um). Since you are isolating the best parts, you will also end up with extract on the other 2 sides of the spectrum. These can be evaluated and then used to smoke individually or mixed together and rosin pressed or added to edibles.

Bubble hash needs to be properly dried and cured or you run the risk of introducing mold. High quality bubble hash can be dabbed, but will leave some residue behind since the waxy membrane is still present.