Rosin Education Blog
In the world of rosin presses, perhaps the most important elements in the extraction process are your heat plates (also referred to as heat platens or simply platens). Heat plates for a rosin press come in a wide variety of sizes and shapes, but they are typically only made with a few different common grades of stainless steel or aluminum. Depending on who you talk to, you will get a different story and many theories currently circulate as to which is better. In this article, we’re going to weigh the pros and cons of the most popular stainless steel and aluminum alloys that are used in rosin press heat plates, as well as discuss other implications with using those metals concerning consumable, concentrated cannabis products.
Virtually all metals come in many different grades, which are determined based on their purity as well as what other compounds (often other metals) they are mixed with. These other metals are called alloys. The metallurgy of each different alloyed metal will offer unique qualities intended for particular applications, so choosing the correct heat plate metal for your rosin press is critical to get the most out of your production. Perhaps the most common grade of aluminum used for rosin press heat plates is 6061 which is treated with magnesium and silicon, otherwise known as aircraft grade aluminum. For stainless steel, some of the most popular alloys are 304 or 316 which contain nickel and chromium, both which have unique properties suited for a wide variety of tasks. Given the amount of metal used in a standard set of rosin press heat plates, cost is typically not much of a consideration.
There are two primary factors you should consider when it comes to selecting which metal you want to use with your heat plates on a rosin press, and in priority they are:
Image Credit: PureTemp.com
The thermal conductivity of your heat plates is arguably the most important factor to consider when selecting which heat plate material you intend to use to press rosin. Even heat distribution + pressure + cannabis material = rosin. Thermal conductivity is typically measured in watts per meter-kelvin, or expressed as ((W/(m. K)). It is also expressed via Fahrenheit in a similar formula, but without getting overly technical, we’ll leave you with the following eloquent explanation. Via Engineering Tool Box, “Thermal Conductivity - k - is the quantity of heat transmitted due to a unit temperature gradient, in unit time under steady conditions in a direction normal to a surface of the unit area.” Each metal has its own k value, with a higher number equating to better, more efficient heat distribution.
Surprisingly, pure aluminum comes in at a k value between 200 to 249, and stainless steel offers a k value of 12 to 45. This means that most grades of stainless steel only offers 6% to 18% of the thermal conductivity that aluminum does. While heating elements deserve their entire own article which we’ll tackle down the road, what you need to know is that stainless steel of virtually all grades, as well as plain carbon steel, are poor conductors of heat across the board, whereas aluminum is considered one of the best. Other notable metals that conduct heat well are gold (k = 318), pure copper (k = 389), or even better, pure silver (k = 407). If someone wants to make a set of pure silver heat plates for us to play with at the PurePressure lab, we wouldn’t mind testing them!
Secondly, durability is the other key factor to consider when selecting a heat plate metal. Metal durability in science is often expressed on the Brinell scale, or, less commonly, the Mohs scale. For our purposes, we believe the Brinell scale is more useful, which is represented as BN. The higher the number, the harder the metal. In this instance, stainless steel is clearly the harder metal, where 316 stainless steel has a BN rating of 217 and 6061 aluminum has a BN rating of 95. Aluminum is often about 57% softer and is more prone to scratching depending on the application and the thickness of the aluminum itself. Unless your heat plates are very thin, there is virtually no risk of warping with either metal. Another factor in durability considerations is corrosion resistance; both aluminum and stainless steel tend to be quite corrosion resistant thankfully. When it comes to rosin press heat plates, extra hardness does not necessarily equate to a longer lifespan however, due to the softness of the materials being pressed. If you were stamping metal instead, stainless steel would likely be your metal of choice.
Given that rosin is made most often with cannabis flowers, kief (trichome heads), or bubble hash, all of which are very soft, you are unlikely to wear out stainless steel or aluminum heat plates even with continuous use. If your heat plates are uneven, contoured, or aren’t precision machined from thick stock material they could wear out quickly regardless of what metal was used to produce them. Furthermore, most rosin is pressed in a polyester, nylon, or silk filter bag between sheets of parchment, which virtually eliminates potential scratching. In some instances woven stainless steel filter bags are used, although far less commonly. These bags could potentially scratch aluminum if pressed without parchment or with thin, low quality parchment paper.
Why Thermal Conductivity Matters Most
When you compare the different qualities that stainless steel and aluminum have, it’s worth understanding why thermal conductivity should be your keystone measure here. Rosin press heat plate thermal conductivity is important because high thermal conductivity aides in the transfer of heat from the heat plates to the material being pressed. Combined with pressure, that heat is used to liquefy your oils and lower their viscosity so they may freely flow from the rosin filtration bag. When the heat is able to transfer efficiently you will liquefy the oils in less time and the oil will raise in temperature uniformly instead of having hot and cold spots. This means that with aluminum, you have greater process control and ultimately a better shot at higher, more consistent yields with your rosin press. The more quickly your oil escapes the heat, the higher the terpene preservation tends to be, which can often increases the quality of rosin tremendously.
Food Grade Designation: Does it Matter?
A commonly touted advantage of stainless steel is that it qualifies as “food grade”, which is determined by the FDA in the United States as a set of guidelines that metals must have in order to safely make contact with food. In fact, many varieties of both aluminum and stainless steel qualify as food grade, along with many other materials that are deemed by the FDA as “Effective Food Contact Substances”. The catch here is that when rosin is pressed between parchment paper, it automatically becomes qualified as a food grade production. This is in reference to the gelatin in parchment paper, hence the food grade qualification. Unfortunately, the FDA has scant information available on the subject and nearly all parchment paper is sold as food grade, whether it is bleached or unbleached. Another issue that is occasionally brought up is the safety of aluminum itself as a food contact metal, which has been demonstrated by the Agency for Toxic Substances & Disease Registry as a safe metal. Both stainless steel and aluminum are ubiquitous in the food industry and aluminum especially is prized for its even heating properties for a wide range of cooking applications.
Conclusion: Stainless Steel vs. Aluminum for Rosin Press Heat Plates
Suffice to say, this is a topic where it’s a little too easy to go down the rabbit hole on material sciences, tensile strengths, and some very complex topics. For the utility of our readers, we feel that the important takeaway is that, above all else, aluminum offers vastly superior thermal conductivity for pressing rosin despite being a softer metal. Poor or uneven heating conductivity can result in low yields and inconsistent rosin, which isn’t what you want when you’re trying to produce the best solvent-less rosin around. The type of metal used in your heat plate is certainly not the only factor involved in heat distribution, but it is a major one, and heating element design deserves its own discussion. It’s worth mentioning that while there are plenty of people who successfully use stainless steel heat plates, they very well could be getting better results with aluminum. As mentioned before, thermal conductivity can have a significant impact on the consistency, quality, and terpene preservation of your rosin.
In conclusion, the engineering staff here at PurePressure strongly believes based on comparing and contrasting the physical properties of stainless steel vs. aluminum that for rosin, you should demand aluminum heat plates in your equipment. Whether you’re using your own at home press or our industry leading Pikes Peak rosin press, we absolutely recommend high quality aluminum heat plates for the best results.
- Very durable, high tensile strength, but offers very poor thermal conductivity
- Very high thermal conductivity, softer, prone to scratching
With so many people making rosin or wanting to make rosin, one of the most popular questions we get asked is, “How do I make amazing golden, clear, or even purple colored rosin?”.
Clarity is seen by consumers as one of the most easily distinguishable factors that separates premium quality cannabis extracts from mediocre concentrates, or worse. This perception was first conceived with BHO (butane hash oil) and other solvent-based extraction methods which pre-date rosin pressing. In fact, most of the same factors that determine clarity are constant between both solventless and solvent-based extraction methods.
In order of priority, the factors that predict clarity when pressing rosin are:
Quality Starting Material
The most important factor that affects clarity when producing rosin is the quality of the material that is being pressed, whether it's squishing bubble hash, kief, or flower. For better or worse, what is considered “great” cannabis versus “average” is highly subjective and depends on what someone is looking for - the factors that determine “quality” can be vastly different from person to person, but a few stand out.
Terpene profile, trichome density, material density, and active cannabinoid content are all measures which can be employed to ascertain the quality of the starting material used. With that said, to simplify things, it is a quality in = quality out scenario. The better the genetics are, the more trichomes that are present, and the way the material was dried and cured all play huge factors in the clarity of rosin when it’s being extracted. The better the starting material, the better the resulting rosin will be in all measures (clarity, yield, and effects).
Age of Material
Second to quality, the age of the material used in rosin extraction is critically important in resulting clarity. The fresher and more recently the material was harvested, the better the resulting color of the rosin will be. As cannabis flowers, kief, and hash age, they oxidize, which over time changes the active cannabinoids present. The aging and storage process, which is also affected by light, greatly determines how clear or dark the resulting rosin extracted from it will be.
Based on our experience and anecdotally the experiences from extractors that we’ve spoken with, the best time to press rosin is immediately after the material is dried and cured. This will be when the material has had the least time to oxidize and, when cured well, will have high manifestations of terpenes. Similarly, rosin that is pressed from very high quality material but which is older and has been through an extensive cure (when done correctly) will often come out darker, but will still taste incredible and provide an excellent experience for the consumer.
Finally, the third key factor that contributes to clarity is the temperature at which the starting material is pressed at. Simply put, rosin that is exposed to high temperatures for too long tends to darken considerably and is subject to a loss of terpenes. Poor heat plate design and hot spots on rosin heat plates from cheap heating elements make for frustrating extracting experiences. There is legitimate scientific evidence which supports the notion of terpene loss at high temperatures, although different terpenes are damaged at different temperature levels. Additional tests have been performed on terpene degradation to oregano and basil leaves with similar results.
Many rosin extractors seem find results in the 180°F - 250°F range, however it is our belief that above 250°F the terpene profile of the material tends to degrade significantly, and we have noticed our best results for both yield and clarity in the 200°F - 220°F range. Temperature will also heavily affect yield, and that the tradeoff is typically the lower your temperature, the better the clarity, but a reduction in yield is frequently realized, and vice versa.
What About Purple Rosin or Ghost Rosin?
There has been a lot of discussion and pictures floating around the internet of purple tinted rosin. While multiple articles have been dedicated to discussing how purple cannabis is grown (see here for a quick explanation), purple rosin is less understood. Typically extremely purple, fresh cannabis flower is the only way to achieve purple rosin, and it appears to be largely based on the plant material itself. If you’re looking to produce purple rosin yourself, your best chance is to start with deeply tinted cannabis flowers to begin with. Based on our testing, some purple flower comes out tinted, and some doesn’t, so more investigation there is warranted to come to firmer conclusions.
Some advanced hash makers are pressing rosin with bubble hash that is nearly white, and are occasionally getting transparent or extremely light colored rosin as a result. This kind of rosin is occasionally referred to as “ghost rosin” but there is considerable controversy behind its quality, and whether or not nearly opaque white shades of rosin are any better than golden shades. With so much experimentation going on with rosin, we fully expect to see a full spectrum of rosin making techniques that contribute to different colors emerge over time.
How Do I Get The Best Looking Rosin Possible?
If you’re aiming to produce the highest quality rosin possible that possesses a golden or even lighter colored hue, make sure that you’re using the best quality input material available to you. In sum, a poor flush, dry, cure, or wash reduces the quality of resulting rosin significantly, and especially material that is old will tend to come out much darker. Temperature is also a major factor, so ensuring that your rosin is never burnt or pressed too hot will help your rosin reach the desired color profile.
The material and the equipment you use play a huge role in the temperature applied when pressing your rosin; even heat distribution and accurate heating are critical to reproducibility and making terrific, high-clarity rosin. Ultimately, all of the factors described here interplay in a variety of ways. If your material is fresh and high quality but it’s too hot, it may tint the color darker regardless, whereas if your material is somewhat old and of acceptable quality, lower heat may still yield the desired result. Finally, we recommend that while keeping quality, age, and heat in mind, go ahead and experiment to see where you find your best results.