Best Micron for Kief and Rosin? 36, 72, 90 or 115?

Choosing a rosin press bag is simple… or is it?

Rosin press screen size beguiles newcomers, but it doesn’t have to. In this guide, we explain why screen size is important and how to select the rosin bag micron size that will work best for you. And, (bonus!) Budsmith, an award-winning rosin producer from Humboldt County, stops by to drop some knowledge too.

What screen size should you use for kief? What micron for flower?

The first thing to consider when choosing a rosin screen size is the material you’ll be pressing. Kief and bubble hash press differently than flower, and their qualities change how rosin flows through the mesh of the bag. When you press flower testing at 20% THC, most of the material isn’t going to flow, whereas with a bubble hash measuring 70% THC, it’s all going to melt pretty easily. Since the material flows easier, we recommend a finer, 36-micron screen for bubble hash/kief if you’re looking for super-quality product. A finer screen helps keep dusty particulate in the bag too. A 72-micron bag is an acceptable choice for kief and bubble hash too.

Since flower rosin has to extrude through all the nooks and crannies of the bud—and because there can be other, larger particulate in there too—it has a little more work to do to get through the screen. So if you’re pressing flower, you’ll probably want to use a larger micron screen like a 90, or 115. For ultra-quality flower rosin, try a 72-micron bag.

“If I’m going for quality, I go with a 36-micron,” says Bud Smith, owner of Budsmith and winner of the Mecca Cup for best rosin. “Nothing over a 72. I’ve used a 25, and I felt like it was holding back a little too much of what I was trying to get out.”

So does the rosin screen size affect yield?

Yes, but not as much as you might think. Mr. Bud Smith (totally his God-given, family name) explains that tightening your screen size will indeed cut your yield a little bit, but the quality tradeoff makes it worth it.

“It’s not a considerable drop-off. If you’re averaging 20% yields from a given strain using a 90, and you drop down to using a 36, you might drop down to a 17% yield,” says Bud. “I exclusively press on a 36 whether it’s flower or bubble hash.” Fortunately, the Triminator’s rosin bags are food grade and boil-resistant, so feel free to be creative and get that last 3% out of there! Tincture? Christmas cookies?

Not everyone is as quality-focused as Bud, so some prefer a 90-micron, 115-micron, or 120-micron bag for mass production. These sizes are all great for flower, depending on the product you’re creating. But in the rosin industry, screens looser than 120-micron are seldom seen. This is because trichrome heads themselves—the most cannabinoid-rich part of the plant—are 120 microns in diameter or a little smaller. Even though the trichromes melt, this is still an obvious choice for the upper size limit on rosin bags.

But what about pressing rosin with no bag at all?

“Sometimes, I don’t use a screen when I’m just pressing off some flower for myself to smoke. You’re gonna get a lot of the essential oils from the plant and the little bits, the orange hairs,” says Bud. Flower rosin pressed without a screen is one step in the direction of traditional smoking and one step away from the candy-sweet experience of dabbing. There’s truly no wrong way to consume this plant! If you’re pressing a small amount, or if you just want to save a couple of bucks on a bag, processing flower in the buff may be the way to go. Consumers, however, typically want clarity and don’t want to see chunky stuff in their retail products.

What rosin bag material should I use?

Nylon is the best material for rosin bags. Silk is prone to blowouts because it doesn’t flex like nylon (AKA polyester). Metal screens mar the surface of the platens when under high pressure.

Can you reuse your rosin bag?

Professional pressers like Budsmith frown on the reuse of bags. Some folks may clean their bags with ethanol and give them another go, but remember that they’ve been stressed under 20,000 pounds of pressure. The pores of the bag have stretched and widened, particularly along the edges where the screen size most counts, and they’ll be partly plugged with plant residue—even if you clean them well. Can you reuse them? Yes, but they’ll be a little less accurate and a little more prone to blowouts.

Avoiding blowouts and broken rosin bags

Most blowouts occur when the technician overfills the bag. For our 9-by-2.5-inch bags, an ounce of flower is a good guideline. Attempting to process any quicker than one ounce per bag risks breakage. Bud makes an additional caution to those pressing hash or kief: go slow. 

“With the bubble hash and the kief, if you apply too much pressure too fast, it blows out no matter how much is in there,” says Bud. “With that fine of a powder, the pressure doesn’t have anywhere to go. Flower is more spongy.” Using rosin pre-press molds also helps reduce bag blowouts. 

What’s a micron anyway? How is mesh size different?

A micron is 1/1000 of a millimeter. There are a thousand millimeters in a meter, so, long story short, a micron is really small. Human hairs are about 100 microns across.

“Mesh size” confuses things when we talk about rosin bag size. Mesh size is more like the thread count density of the sheets on your bed. Micron sizing refers to the size of the holes between the threads. Mesh size is how many gaps there are per linear inch. But measuring in microns cuts right to the chase and indicates how big those holes are— without having to think about them in terms of per inch. Make sure what you’re buying is expressed in microns rather than mesh size.

How to buy a good rosin bag

“There are definitely low-quality screens out there,” says Bud. “I wouldn’t buy a whole package of something that’s cheap without knowing. I’d buy something you know or something somebody else has used.” Don’t bite off on a 1,000-screen package from eBay. Stick with word of mouth.

So which micron size should I use?

115-micron – Flower and trim rosin at excellent yield with good quality

90-micron – Flower and trim rosin at great yield with great quality

72-micron – Flower and trim rosin at good yield with excellent quality

72-micron – Kief and bubble hash at excellent yield with good quality

36 micron – Flower at decent yield with the best possible quality

36-micron – Kief and bubble hash at good yield with excellent quality

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