How Contaminants Affect Solventless Processing

Contaminants are an issue that continues to linger over the cannabis industry. In recent years, contaminants have been an issue in California as well as in PurePressure's backyard in Colorado, along with just about any other state that actually requires testing for them. The issue extends into Canada as well, where an estimated more than 5 million Canadians aged 15 and over are sourcing cannabis through illegal means. 

Additionally, a Bloomberg report found that 98% of products from over 300 CBD merchants were non-compliant with one or more regulations. In one case, a CBD product contained more than 18.5 times the amount of allowable lead. 

A wide-ranging array of elements has the potential to contaminate cannabis products, be it cannabis flower or its extracted concentrates. Concentrates production, specifically solventless extraction such as rosin pressing and ice water hash washing, do not remove contaminants during the extraction process. This is mostly a good thing, as it means that when your rosin passes testing it was made with great material, but it also means that pre-contaminated product typically cannot be used for solventless. Any contaminants found in the plant before extraction will carry over to the extracted oils and products. 

Concentrate producers and cannabis cultivators alike must understand the common contaminants that may potentially cause their products to fail tests, waste products and harm your bottom line. 

Whether cultivating the crops yourself or sourcing from partners, keep in mind these common contaminants before they cause your products to fail its testing. 

Common Contaminants in Cannabis 


A fungus is a common culprit when it comes to rosin and hash contaminants -- or any concentrate for that matter. Developing in moist and warm locations, various types of mold have been known to ruin crops and the concentrates they could produce. 

When pressing flower rosin, you would need a screen in the 1 to 5 micron range to filter out mold, which simply isn't feasible. For this reason, it's crucial to press only flower that you know is mold free. Here are a few examples of mold to look out for.

White Powdery Mildew

Leaves can appear dusted in a layer of white, but don't confuse them for trichomes. Upon closer inspection, you'll see that you're dealing with mold. Watch out, it often appears quickly, spreading throughout your crops soon after if not swiftly addressed. 

Grey Mold

Developing in your buds and growing out, grey mold is caused by moisture remaining inside the cannabis' colas. A limp or dry leaf can be an indicator. Any appearances of grey mold should be removed from your grow as soon as possible or risk affecting nearby plants. 

Ice water hash contaminants are a particularly common issue. Mold tends to develop during the hash drying process with producers who use air drying techniques. When letting your concentrates to air dry, high moisture concentrations are allowed to linger for days, leaving your concentrates exposed to a higher risk of contamination. 

We recommend using a freeze dryer to take care of this before it becomes an issue. Freeze dryers allow producers to control their drying in ways that the elements simply won't allow. In doing so, you give yourself a better chance to preserve terpenes, enhance product clarity and upgrade the overall quality of ice water hash, as opposed to air drying.

Heavy Metals

Cultivators use fertilizers and soils which contain may contain metals like cadmium, arsenic, lead and mercury to name a few. Depending on the state, producers are allowed to have a certain amount in their crops before it is deemed toxic, commonly considered as heavy metal.

We reached out to Kristen Goedde, the founder and COO of Trichome Analytical, and she told us the following: 

"Heavy metal contamination is found in varying amounts throughout the plant (roots, stems, leaves, flowers, seeds). Trichomes are also known to accumulate heavy metals, and cannabis is covered in different types of trichomes. From contaminated soil or water, cannabis will uptake heavy metals through the roots and disperse throughout the plant. Typically, the highest levels of contamination are found in the roots and leaves."

This means that heavy metals can be present in virtually all parts of the cannabis plant if they are present in the soil for uptake, and that in the solventless extraction process, there is no escaping them. It's still unclear if this is the case with hydrocarbon and other forms of solvent-based extraction, but it certainly seems likely that heavy metals would carry over in those methods as well. 

Exposure to heavy metals can lead to several outcomes, depending on the metal and its concentration. In milder cases, a person can experience headaches and nausea. More significant consumption can lead to organ failure and cancer when exposed for prolonged periods.  

In June 2017, Advanced Nutrients’ Michael "BigMike" Straumietis told Cannabis Business Times how smoked heavy metals mimic other essential elements, which can lead to the metals replacing the elements in bones and other cell processes. 

"In short, these metals bind with sites which were not originally intended for them and, in the process, they remove the original metals from their natural binding sites. This is what causes the malfunctioning of cells and, ultimately, toxicity," he explained. 

In the years since that interview, heavy metal testing has improved. In California, producers now must test for heavy metals in all retail products. 

Pests and Pesticides

Pesticides remain a pressing concern for cultivators and producers alike. Pests are common in both indoor and outdoor grows. For outdoor cultivators, the risk appears to be the highest when the flowering process commences. Meanwhile, indoor grows can expect insects as the temperatures reach their peaks for the year. 

To counter this issue, cultivators employ various insecticides and fungicides to fend off any insects. Some of these pesticides are chemical-based, and often used during more substantial infestations. These chemical pesticides can remain on mother plants for years and can lead to your cannabis products failing its testing. 

If possible, indoor growers can treat infestations without using chemicals by using organic cleaners or remove the plants from the grow and washing the plants with significant amounts of water. Once dried, a natural pesticide can be applied and repeated every few days.

In the ice water hash washing process, make sure you always use RO water, as distilled water actually concentrates any existing pesticides that may have been contained in the water, even in trace amounts. 

Various State Testing Regulations

Before taking your operation to another state, consider the rules. With a fragmented, unregulated American cannabis market, each state is left to create its own rules. As such, what may be the case in California is not the case in Colorado, Oregon, Illinois or elsewhere. The rules can often be complicated and challenging to keep track of. What may have been allowed in one state is not in your new market. 

Be sure to have a compliance policy in place that reflects the demands of each state your business operates in. Doing so minimizes the risk of losing products, money or even your license if a significant issue were to arise. A compliance policy can include outside testing, a compliance officer, a legal team or other similar arrangements that meet the needs and size of your business. 

Your compliance policy should also account for any potential failed tests. We recommend this policy contain a retest policy. If a sample does fail, have it tested again to ensure that no processing errors occurred. From there, you can take the appropriate measures depending on the results of the two tests. 

Finally, remember that solventless processing can be more affected by contaminants than other extraction methods because whatever is in your starting material will end up in your rosin or hash.