Rosin filter bags offer many advantages to solventless extractors. They keep cannabis material tight and compacted for a consistent flow of rosin, facilitate even pressure from the heated plates onto the material throughout extraction, and help remove unwanted lipids and plant particles from rosin. Rosin filter bags are a staple of the solventless extraction toolkit. But can you press rosin without filter bags?

The answer depends on what type of cannabis material you’re pressing. While technically you can press any material without first placing it into a rosin filter bag, the results can vary from acceptable to downright lousy. Some material just doesn’t yield good results without the help of rosin bags. 

Pressing bubble hash requires the use of rosin filter bags, while pressing flowers without rosin bags can still give you a good product (if done correctly). Let’s look at the mechanics of pressing rosin in more detail, and see why rosin bags play such a key role in a successful extraction. 

Pressing Bubble Hash

Bubble hash is a type of solventless concentrate that’s composed almost entirely of full mature trichome heads - the sparkling, resin-packed globes containing high amounts of therapeutic compounds. After bubble hash is dried and prepared for rosin extraction, it has a consistency like sand, a granular material composed of thousands of trichomes held together by trace amounts of sticky cannabis oil which coats their surface. Unless it’s heated and intentionally pressed into blocks or balls (e.g. Temple Balls), bubble hash takes on nebulous, formless blobs. If pressed between heated plates by itself, bubble hash will spread out thinly like a pancake, and maintaining an even level of pressure on the material proves to be elusive. 

Additionally, bubble hash produces an exceptionally high-volume flow of rosin. Pressed by itself, the unwanted components of bubble hash (e.g. trichome membranes) will flow out of the hash along with the rosin. Bubble hash easily mixes with the rosin that’s extracted from it. 

So if you’re pressing hash rosin, rosin filter bags are a necessary part of the process. 

Pressing Flowers

Cannabis flowers are covered in trichomes, but the ratio of plant material to trichomes is much greater than bubble hash. While bubble hash is made almost entirely of trichome heads, cannabis flowers are mostly composed of plant substance with a coating of trichomes. Cannabis flowers hold their form much more readily than bubble hash, and even under the heat and pressure of rosin extraction, the buds stay relatively intact as the rosin flows out. The flower material can still remain relatively self-contained and separate from the rosin that is squished out during extraction. 

Although flowers will spread out between the plates when pressed without a filter bag, it won’t happen to the extent that it does with bubble hash. It’s still possible to maintain pressure, and keep an absurd amount of plant material out of the rosin, when pressing cannabis flowers without a rosin filter bag. 

Preparing Flowers To Press without a Rosin Filter Bag

Pre press molds make it easy to compress your flower in preparation for pressing without a bag. Pre pressing is beneficial when you’re using a rosin filter bag, and it’s crucial when pressing without a filter bag. Pre pressing compacts the cannabis into a dense rectangle (or round puck if you’re using a pollen press-type mold). If you’re not using a filter bag to keep all the material confined to a fixed area between the rosin plates, it’s important to at least get the material into a relatively consistent, solid mass. 

Learn more about pre pressing in How To Use a Pre Press Mold. 

Disadvantages of Pressing Rosin without a Rosin Filter Bag

It is possible to press flower rosin without a rosin filter bag, but there are disadvantages. Lack of filtration is the most significant downside. Filter bags hold back significant amounts of lipids from escaping the source material during extraction. Without filter bags, more unwanted plant lipids flow through with the rosin, bringing the potential to negatively impact flavor. 

Another disadvantage to pressing without a filter bag is having less control over Platen PSI. Platen PSI measures the amount of pressure being applied directly to the source material, not simply the output of your press. Platen PSI depends on the area that your material occupies between the plates. With a rosin bag, that area is more fixed and therefore predictable than the area of material without a bag, since the material will spread out considerably under pressure without a bag to confine it. Pressure is harder to dial-in when pressing without a rosin filter bag. 

Learn more about Platen PSI in our article How To Calculate Platen PSI.

Also, if you're looking to extract THC-A rosin, then rosin bags are a must. 

Recommended Approach

Rosin filter bags are a must for pressing hash rosin. Double-bagging is a common practice. We recommend a 37 micron on the inside with a 120 micron on the outside. 

While rosin bags are optional for flower rosin, we recommend using a 90-micron rosin bag for the filtration power and control of pressure during extraction. Rosin filter bags produce a cleaner rosin, filtering out even plant material and lipids that aren’t visible to the naked eye. 

Read more about the advantages of using a rosin bag in the article Rosin Bag or No Rosin Bag?

Also, learn more about How To Pack Rosin Filter Bags.

Conclusion

For many extractors, the downsides to pressing rosin without rosin filter bags are greater than any potential upside. Bags offer clear advantages when pressing rosin, filtering out plant contaminants and excess lipids and helping to maintain a consistent level of pressure on the material during extraction. 

However, if you want to press flower rosin without a bag, it’s definitely possible. Just be sure to pre press the material and expect some contamination in the rosin, even if it’s microscopic. Pre pressing is the best way to prepare flower for pressing without a rosin bag. But at the end of the day, we recommend using quality rosin bags to create the purest rosin possible. 

Do you prefer to press flower rosin with or without rosin filter bags? Let us know in the comments!

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FREQUENTLY ASKED QUESTIONS

Can you press bubble hash without a rosin filter bag?
It's not feasible to press hash without a filter bag. The heavy flow of rosin and consistency of the hash require a rosin bag to press successfully. 

Can you press flower rosin without a rosin filter bag?
It's best to press with a rosin filter bag, but you can press flower rosin without a rosin bag. 

How do you press flower without a rosin filter bag?
Pre pressing the material into a compacted form is necessary preparation for pressing flower rosin without a rosin filter bag. 

What is the problem with pressing rosin without a rosin filter bag?
There's higher chance for contamination in your rosin, and less control over pressure, when pressing flower rosin without a rosin filter bag. 

Why is it better to press rosin with a rosin filter bag?
It's best to press rosin with a rosin filter bag in order to keep contamination from getting into your rosin, and also for better control of pressure on your source material during extraction.