November 11, 2020 6 min read

By George Mouratidis

If you’ve just purchased your first rosin press or plan to make bubble hash, you’re probably wondering which micron bags to use or if you even need to use filter bags at all.

Let’s examine some of the ins and outs of micron bags and find out more about some of the best micron bags available in 2020.

What are Micron Bags Used for?

Micron bags are used to filter plant matter out of solventless extractions like rosin and bubble hash.

Plant particles not only make your extractions less tasty, but they also can clog devices like vaporizers designed for concentrates. 

The word “micron” refers to the size of the holes where the extraction filters through.

A micron measures 1/1000 of a millimeter, so you can imagine how small the filter holes are on some micron bags. Some of the finest-gauged micron bags have holes less than half the size of the average human hair.

3 Types of Micron Bags

1. Rosin Press Bags

Rosin press filter bags are usually made of food-grade nylon mesh, similar to a reusable coffee filter.

Micron rosin pressing bags come in different sizes and gauges you can use for different materials. A few companies make silk micron bags, but they’re more delicate and prone to blowouts. 

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Most of the top-brand rosin press manufacturers, such as PurePressure and Rosin Tech, produce their own line of micron bags. Off-brand micron bags may be cheaper, but they’re more prone to blowouts and can be made of inferior or unsafe materials.

Rosin makers place their filled micron bags between a folded piece of parchment paper before pressing to help collect the rosin.

2. Bubble Hash Bags

Bubble hash bags, or bubblebags, are used for making solventless hash with ice and water. Bubblebags are usually sold in kits containing a bucket and several sizes of differently gauged micron bags. The extracted material filters through micron bags with increasingly finer-gauged holes to make hash. Bubble hash makers place the bubble bags in the bucket one inside of the other starting with the smallest micron gauge. 

3. Stainless Steel Screens

Stainless steel filter material comes in flat sheets or rolls and different micron gauges. You can use stainless steel micron material to customize the bag size for your rosin press. However, some rosin makers feel that stainless steel filters affect the taste of their concentrates.

Most of the best micron bags are made by the same manufacturers that produce high-quality rosin presses, such as:

Companies like PurePressure sell complete rosin-pressing accessory kits, which include micron filter bags.

Micron Bag Sizes and Gauges

Your project, your rosin press, and your personal preferences will decide which size and gauge of micron bags to choose.

Micron Bag Sizes

Manufacturers usually measure micron bags by the dimensions or in terms of grams. Some of the most common micron bag dimensions range from 2” x 3” to 2.5” x 9”.

Rosin press manufacturers may offer less-common micron bag dimensions that have been customized for their equipment. Gram sizes typically range from 3.5 to 14-gram bags.

Micron Bag Gauges

The gauge of micron bags you choose for pressing rosin depends mostly on personal preference.

There’s a delicate balance between optimum quality and yield. It’s up to you to find your sweet spot and choose the best micron bags to suit your purposes. Standard gauges for micron bags are 15μ, 25μ, 37μ, 72μ, 90μ, 115μ, 120μ, 160μ, and 180μ.

Some brands like NugSmasher and PurePressure offer variety packs. You can try out different options before investing in larger packages of your favorite micron gauges.

In general, a smaller gauge will give you a purer extraction, and larger gauges allow more plant material to enter your finished product.

Your choice of micron gauge depends heavily on the starting material you’re using. Flower, trim, and shake have a high quantity of plant matter and don’t allow the rosin to flow through the filter as easily.

You’ll need to start with a micron bag with larger holes before switching to a smaller micron gauge.

Kief and hash, on the other hand, have fewer plant particles to clog the holes, so you can start pressing these materials with a smaller gauge of micron bag.

Each material will have its own characteristics, but here are a few guidelines and starting points for you to begin your experimentation:

  • Flower: The ideal gauge of micron bags to press rosin from flower sits between 90μ to 120μ. That said, some makers of ultra-premium rosin use micron gauges as fine as 36μ. You may want to start with a 115μ micron bag for the first press and check the quality-to-yield ratio before experimenting with finer gauges. The individual strain and the flower’s freshness will also determine which gauge micron bag you use for pressing rosin. You can use the same procedure to test the optimum micron bag gauge for trim or shake.
  • Kief: You’ll need to use a finer gauge of micron bag for pressing rosin from kief. Kief contains much less plant matter than flower, and some of the highest quality dry sift is comprised of almost pure trichomes. Most rosin-makers find the ideal range to press kief at between 25μ to 90μ. We recommend that you start with a 45μ micron bag and gauge up or down from there.
  • Hash: You can press hash with around the same gauges as kief, depending on the quality. Higher-end hash may make the best rosin using 25μ micron bags.

Mesh Size

Consumers often confuse mesh size with micron gauge, but they’re two different things. Mesh size measures how many gaps per linear inch, similar to thread counts with fabric.

Rosin makers should pay more attention to the micron gauge instead of the mesh size when choosing micron filter bags.

How to Use Micron Bags to Press Rosin

Some rosin-makers choose to fill their bags flat, while others prefer a barrel orientation. We suggest that you begin by following the manufacturer’s instructions for your first pressings and experiment after you get the hang of using micron bags.

Whichever approach you select, you’ll need to make sure that the seam is turned toward the inside of the bag. This precaution will keep your rosin from getting stuck in the seam. Some companies, like Rosin Tech, make seamless micron bags, so you won’t need to worry about this step if you use them.

It’s also important to remove as many stems as possible and break up your flower or other material into smaller chunks. Additionally, you should be careful not to overfill the bags as they may break open at the seams. Another way to avoid blowouts is to preheat the material first and press your rosin slowly.

Flat-Pressing Method

Most rosin makers load micron bags using the flat-pressing method. First, you invert the bag so that the seam is inside. Then, you lie the bag flat and fill it until you have a layer of material no more than ¼ inch thick. It’s crucial that you don’t leave gaps or overfill the bag. After you fill the micron bag, cut off any extra material, and fold the bag closed.

You can make flat pressing easier by investing in a rosin press mold. Molds give your rosin a nice shape and help to prevent micron bag breakage.

Bottle Tech Style Rosin Pressing

The bottle tech style of filling micron bags involves standing the bags up vertically to create a cylinder shape. Here’s how:

  1. Invert the micron bag so that the seam is on the inside.
  2. Push the two bottom corners inward to create a slightly conical bottom.
  3. Fill the bag so that there are no empty spaces where rosin can collect.
  4. Cut any excess material from the top of the bag.
  5. Fold the top of the bag inward to close.

Additional Tips for Pressing Rosin with Micron Bags

Rosin pressers employ a host of other tips and tricks. For instance, some people choose to do their first pressing with a larger gauge before doing a second pressing with a finer micron bag. Others double-bag their material to create even higher-quality rosin. 

Some people who press rosin forego the bags altogether to save money. If you choose to go the no-bag route, be aware that your rosin will likely contain plant particles.

The plant matter will detract somewhat from the flavor of the rosin. The difference in quality may not matter so much for people who are only pressing a few grams for personal use. However, people who plan to press larger amounts of rosin or who want to create the highest quality concentrate shouldn’t skip the filter bags.

While it’s possible to clean and reuse rosin bags, it’s not the best practice. Used micron bags are more susceptible to breakage. If you have no choice but to reuse your rosin bags, you can clean them by soaking them in alcohol or boiling them in oil.

If you have any more questions about rosin pressing or would like help choosing micron bags, rosin presses, or accessories, please contact us at

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