🇺🇸 Retired veteran, father, rock-climbing expert & rosin connoisseur
If you’re like me, knowing how things work is almost essential. While I’m not a perfectionist, it comes without saying that if your going to do something, then you need to do it right. Without the correct pressure applied to your buds, yields will drop and you risk running under heat for too long, which will change the flavor and threaten the integrity of your final product. Now by all means I’m not telling you to use the entire potential of your press unless it is absolutely necessary. There are two ways to figure out the PSI applied to your product. You will either need to do math or invest in PSI gauge for your press. I cannot stress enough that the measurements of PSI we are looking for are at the bag. Not the plates.
If you have a 7 ton press then you know how hard your press can squeeze the buds. Which would be 14,000 PSI. This number is broken down over the surface area of 1 square inch. As most of us are using Rosin bags when we press, the surface area will be directly related to the size of the bag. If using a 2”x4” bag you would take two inches off the length (for the fold and trimming) and would be left with a surface area of 2”x2”. So you will need to use your math skills to figure out the applied PSI to the bag.
The math: Pressure(PSI)= Force(LBs) / Area(IN^2). For the area we are going to use the number of 1.8” to account for the seem stitched in and a bit of bag flex.
So we plug in our numbers...
Just for reference... a bag that is even just slightly filled more will change the pressure quite a bit. Even if it’s just an inch.
This is a massive difference in PSI and is not even close to suitable for flower. At a minimum you would need around 600PSI to press flowers and approach a 30% return. As always, quality in equals quality out. 1000PSI tends to be the maximum amount of pressure you would want to exert on flowers. To me this is a personal preference as I do not want to press any of the plants’ material into my rosin. (Im talking about plant lipids and even chlorophyll) Higher pressures than 1000PSI may yield fractions of a difference more in return, but potentially ruining the quality of your rosin.
Pressing bubble hash and kief require you to press lightly. In the 300 to 800 PSI range. Bubble hash being closer towards 300 and kief closer to 500. Do not press these excessively, as blowouts are much more common and nearly impossible to get your rosin clean of the plants material. Using Press Club bags can minimize this from happening due to their well made nature.
Things get really interesting when you have the math to back up your pressing. Because, now things are easily repeatable and recipes will tend to take shape. Remember to right your findings down and if you are lucky enough to be using a pressure gauge make sure you are using it properly and reapplying pressure as needed. Sometimes in that 90 seconds of pressing, things will begin settle in and you may have to add some more pressure back to the bag every 30 seconds or so. So keep pressing and take the opportunity to learn from each batch of Rosin that you press.