How to Sift Kief - The Science of Cannabis Sifting

First Published: June 3, 2021
Updated: February 29, 2024

It may all start with the grind, but it certainly does not end there. If you’re not sifting your flower too, you are missing a vitally important step.

Commercial sifters are changing the game for commercial pre-roll production.

In the past, we have written a lot about the end-to-end pre-roll production process to make sure you have a comprehensive view of how to produce the very best pre-rolls. But today, we are going to zoom in on the sifting portion of the process to examine why exactly sifting is helpful. Plus we’ll run our own sifting experiment to see if those benefits play out in an actual production environment.

As Pre-Roll Experts, we never sell any pre-roll production equipment that we have not brought into our facility and tested ourselves to deeply understand how they work. So, we can say without hesitation that our sifting machines are a secret weapon behind the highest-quality pre-rolls on the market.

Though often neglected, sifting is a crucial step that removes any stems that get through the grinder, along with any other foreign material or large particles that might tear or break your cones when you go to fill them. It's a simple step but if overlooked it can lead to uneven, broken and overall poor-quality pre-rolls.

And nobody likes that.

But even more important than removing stems from the material, the sifter helps ensure an even particle size distribution across the ground material. That means that each individual particle is a similar size to the particle next to it.

And in commercial pre-roll production, consistent particle size is more important than you might think.

Particles and Flowability

So, beyond filtering out stems and foreign materials, how does sifting help in pre-roll production?

Scientists who studied the effect of particle properties on the flowability of ibuprofen powders found that, for powders with a narrow size distribution, the flowability increases significantly with the increase in particle size.

When we provide a grind which is not a fine powder and we ensure that the ground material has a narrow particle size distribution, we will see improvements in flowability. Therefore, it is extremely important to be focused on your particle sizes and the distribution of particle sizes.

Or as they put it in the KONA Powder and Particle Journal: "Any manufacturing operation that uses powders as one of its raw materials will always find one of its bottlenecks is cohesive powder flow."

By controlling the size of our particles through our grind and narrowing our particle size distribution through our sifter, you can create a free-flowing powder, which will allow you to make pre-rolls that are well packed throughout from crutch to tip. Not only will you make better pre-rolls, but you will make pre-rolls faster.

The Numbers Don't Lie

As an example, if you were to fill two pre-rolls: one with sifted material and the other with un-sifted material, you can really tell the difference. And when this is done across 169 pre-rolls (using a King Kone filling machine, for example), the numbers don't lie.

We did a run with un-sifted material and the weight variance was 65% higher than the sifted material. The number of pre-rolls that had a hole due to stems was 488% higher than the sifted material. The number of pre-rolls with an unsatisfactory pack was 194% higher than the un-sifted material.

Out of a run of 169 pre-rolls, you will get 27 more pre-rolls when you use sifted material versus un-sifted material. When you start to think about scaling up your production, the value of a sifter becomes clear.

For the purposes of our experiment, we used our QuickSift Mini, but you can also purchase two larger-size sifters: the Quicksift Commercial and the QuickSift Industrial, which easily accommodate larger volumes. Each of them can be purchased with a variety of different mesh screen sizes to get exactly the grind consistency you want for each of your flower strains.

This is even more important if you are using an automated pre-roll filling machine, because consistent particle size is a necessity to keep things moving, with some machines even requiring exact sizes to work properly.

For example, machines like the AuraX and AuraOne, need a particle size of between 1-5mm in order to keep things moving. The Aphehex machine needs are even more specific, recommending a particle size of 2.5mm sifted through a 1/8-inch screen for optimal performance.

Sifting for better pre-rolls

Beyond the speed, consistent particle sizes lead to better-packed pre-rolls. And better packed pre-rolls are better smoking pre-rolls.

This is because different sized bud particles burn at different rates, with smaller particles burning hotter and faster than larger ones. Different particles sizes also prevent smooth airflow through the pre-roll and can lead to uneven packing or gaps inside the pre roll. All of these can lead the pre-roll to canoe or run, burning unevenly down one side of the cone.

There’s nothing worse than losing half your pre-roll because a bad pack has caused it to canoe, and in the modern, competitive pre-roll market, that can be enough of a reason for someone to reach past your product and try someone else’s.

When selecting a screen, it is important to remember that the larger the number, the finer the mesh on the screen. That means small numbers lead to larger particle sizes and higher numbers get you smaller ones. When sifting for pre-rolls, we recommend starting with one of our most common screen sizes, either a 10 or a 12 mesh, and the adjusting up or down in size depending on your flower and results.

Sifting for Better Metering

Sifting your already-ground cannabis prior to filling your pre rolled cones can not only better packed, but more consistent pre-rolls as well, particularly if you are using a metering tray, like those that come with many tabletop pre-roll filling machines, such as the King Kone pre-roll filling machine.

Metering trays, which help ensure that each pre-roll is a consistent weight and fill, work by volumetric filling, which means that instead of a measure of weight, the trays use volume –or the space filled by the cannabis – to try to ensure a similar amount of flower makes its way to each pre-rolled cone. Because of that, the trays are only accurate if the volumes are uniform across the tray.

Sifting your cannabis prior to loading it into your trays helps ensure that the particle sizes are all the same, leading to more accurate volumetric measurements and more consistent pre-rolls in general. This can save valuable time and employee hours, and we all know that every dollar matters in the modern cannabis industry.

It’s even more important for companies that use shredder-style or whip-style grinders, as those machines often create a wide range of particle sizes, from dust to larger chunks of flower, which can create inconsistent weights, even at the same volume measurements. That, in turn, can lead to unevenly filled pre-rolls, which can lead to canoeing, a potential revenue-killer in such a highly competitive sector of the market.

Sifting for Kief

If kief collection and application is part of your production of infused pre-rolls, then sifters can help you out there as well.

Kief is the white or golden dust made of the trichomes that comes off of bud as it is handled, including grinding or sifting. The trichomes, which look like tiny crystals, are where the terpenes and cannabinoids are made. When they break off, they are called kief.

Kief can be used in a variety of ways. It can be made into a dry-sift live resin and used to make hash. It can also be used to make infused pre-rolls, either by mixing it with your flower or applying it to the outside of your pre-rolls, using hash oil as an adhesive.

Whereas the focus when sifting should primarily be to reach a consistent particle size to smooth the production process, you can get much finer mesh screens that are specifically designed for kief extraction, a process that separates the cannabis trichomes from the plant itself.

Selecting a screen for kief is different from selecting one for packing a specific particle size into pre-rolled cones. Kief is a much smaller particle than what you need for packing a pre-roll, so be sure you search for a higher screen size number since when it comes to screens, the higher number means a smaller particle size. We recommend a starting screen size of 80 or 100 mesh when screening for kief and then adjusting up or down as needed.

Final Thoughts

Sifting the cannabis that goes into your pre-rolls is an often-overlooked but critical step that not many pre-roll manufacturers opt to skip, and we guarantee it shows in their end product. That’s no coincidence.

Particle size and particle distribution have a scientifically proven impact on the flowability of air through the pre-roll, which in part determines how the pre-roll burns. And as our experiment found, it also factors into the speed with which you can produce pre-rolls.

So while sifting may be just a small step in the process, it can add tremendous value for both you and your customers. Talk to a Pre-Roll Expert today to find the sifter that is right to help take your business to the next level!