Updated May 6, 2022
Quality is King, Followed By Freshness
This sounds like a no-brainer but time and time again we talk to customers who are pressing flower and are getting poor to average results. Almost always it’s because they are squishing poor to average flowers, which is perfectly fine, but if you want stellar results, you need stellar material. This doesn’t mean that you have to go purchase “Platinum Gold Seal” off the shelf buds at your local dispensary or fill your entire garden just with Gorilla Glue #4, but with rosin, your results are mostly predetermined in the garden if your plates are up to par.
Quality is also closely related to freshness and you will often see your very best results when pressing flowers as soon after they are dried and cured as possible. The longer you wait, the darker it will be (oxidization), so make sure to squish buds when they’re as fresh as possible.
Similarly, we have not noticed perceptible differences between the flower rosin pressed from hydro, soil, coco grown flowers - the grow media plays a factor as far as the skill of the grower is one of the biggest determination with each particular grow medium. That being said, some strains and types of cannabis flowers do tend to yield better than others, namely indicas and hybrids anecdotally do better than wispy sativas.
Your heavy hitter, ultra-potent plants are usually going to be big yielders as the resin production is elevated with genetics such as Gorilla Glue, Ghost Train Haze, and many more. When it comes down to it, the biggest determination for yield, flavor, and quality is all based on how well the material was grown and how strong its genetics were in the first place.
- Relative Humidity Makes or Breaks Yields
Another major factor that we determined after many flower rosin presses is that the humidity and moisture content of your buds will make a massive difference for your flower rosin yields. The reason for this is that if your cannabis is very dry, it will act like a sponge when the trichomes are liquefied, thus soaking up much of the rosin before it has a chance to escape. When you press your flowers, always make sure the relative humidity content of your material is at least 60% to 65% for optimal results.
You can quickly and easily check the moisture content of your flower by using either an analog hygrometer, such as the kind found in many cigar boxes.To increase the humidity levels of your buds, you can pick up pre-set humidity packs from Integra or Boveda; both companies sell packs that get your material to a perfect 55% (good for curing and joint smokers) 58% (good for joint smokers) or 62% (good for rosin pressers) moisture level. Moisture levels are a personal preference when it comes to joints..but when it comes to rosin pressing..there is ONLY one RH to use and that is 62%! Easy!
- Choose a Temperature Based On Your Desired Results
Temperature is perhaps the most debated variable in the rosin pressing equation today, with fierce proponents on both sides of the spectrum (hotter vs. colder pressing). When you apply heat and pressure to your flower, the speed and consistency in which the trichomes liquefy depends greatly on what temperature is being used, as well as the evenness of that heat distribution. Generally, there are two accepted ranges within which to press virtually any type of rosin.
- Cold Pressing: 60°C - 85°C (140°F - 185°F), pressed for between 1:00 and 5:00 minutes or longer, which often produces a budder or batter consistency. Rich terpene preservation, but sometimes with a sacrifice in yield.
- Hot Pressing:86°C - 100°C (187°F - 212°F), pressed for between 0:45 seconds and 3:00 minutes, which frequently produces a very oily or shatter-like consistency.
- High terpene preservation if pressed at 90°C (194°F) or below, often accompanying an increase in yield over cold pressing.
In our opinion, we have found the most success around the 70°C - 90°C (158°F - 203°F) range which offers a great compromise between quality and yield. If terpene preservation and quality is your #1 goal, you should probably start colder and evaluate your results, however we have observed very little terpene loss in that range. Above 100°C (212°F) however there can be noticeable losses in flavor and terpenes. Try and see what works best for you, but heads up once you hit the higher temperatures. Pay attention.
- Choose The Correct Micron Bag
First and foremost, you can absolutely press flower rosin without a bag if you want, but you are liable to get little bits and pieces of plant material in your rosin on the other end. If you are pressing a rosin filter bag however, getting the right micron screen size is essential in order to strike a great yield-to-quality ratio. The rule of thumb is that you should never press flower rosin in anything less than 90 micron width. Below that, you can compromise your yield without getting noticeable gains in quality. Similarly, anything above 150 micron width tends to not filter that well, so reductions in quality may be realized. The relationship between micron type and material type is very important, because the higher the micron count, the more porous the mesh filter is.
- 90 Micron: best filtration and highest quality output for flower rosin, some reduction in yield
- 115 Micron: best overall micron filter type for flower rosin, a great sweet spot for yield and quality
Also, always make sure if you’re pressing in a bag to use 100% polyester monofilament filter mesh (nylon), which is the most conducive for yields while also being one of the FDA’s top recommended food grade fabrics. Stainless steel screens are prone to scratching plates and cutting yields, whereas silk screens stretch a significant amount, making it difficult to accurately track your pressure data.
- Extra Pressure Doesn't Always Make a Difference
Finally, while flower rosin requires more pressure than kief and hash rosin to squeeze all the juice out, what many high tonnage presses apply is absolutely overkill. We’ve found that the ideal pressure range for flower rosin is between 1,000 - 2,000 PSI at the plate, with maximum quality being on the lower end of that range, around 1,200-1,600 PSI. Many DIY bottle jack presses can offer as many as 20 tons or more of pressure, but at very high applications of force, undesirable particles and plant lipids can also be extruded into your rosin. We’ve achieved yields above 25% with flower rosin at as low as 1,000 PSI, when pressing high quality buds with proper moisture levels.
To calculate pressure and figure out what you’re applying, take the total amount of force exerted by your press, and then divide that amount by the total square inch footprint of your rosin filter bag or the contact point of the material being pressed. This is another highly contested and controversial topic, and we do not want to assert that what we have found is the only way to do it. If you’ve experienced success with high pressures, by all means, keep it rolling. We just suggest perhaps trying lower and seeing what you get, as we’ve noticed great results without going way overboard on pressure applications.
Here’s an example with our own CannaPlates 5" X 3" Rosin Kits using a 10 ton press:
Total available pressure: using only 80% of the available 10 tons - 8 tons
Bag used: 2” x 4”, or 8 square inches
16,000 lbs ÷ 8 square inches = 2,000 PSI at the contact point of the bag and the plates.
Yes the entire surface area of the plates is 15 square inches, but you are not using that entire surface area of 15 square inches.
Flower rosin, when pressed from top quality material, is one of the best ways to make an extract. The terpene preservation often rivals or exceeds live resin, which is almost always faithfully represented from buds to oil in the rosin pressing process. If there is anything that you take away from this guide, it’s that quality matters most. Ultimately rosin pressing is a community of experimentation. Keep experimenting and sharing your information. This only makes us stronger.