water drop

Water Activity and Cannabis Testing

All things Water Activity

By definition water activity or aw is the partial vapor pressure of water in a substance divided by the standard state partial vapor pressure of water. In the field of food science, the standard state is most often defined as the partial vapor pressure of pure water at the same temperature. Using this particular definition, pure distilled water has a water activity of exactly one. As temperature increases, aw typically increases, except in some products with crystalline salt or sugar.

Water activity plays a vital role in product quality including:

Seed Storage
The food industry
Tobacco industry
Tobacco Industry
Pharmaceutical and cosmetic industry

Water Activity vs. Moisture Content

There are differences between water activity and moisture content. Water Activity, on the other hand, is a measure of water that is available to react with or attach itself to another material. The process of water attaching itself to other materials is known as sorption. The strength of this combining force is known as the water’s energy level. The higher the measured water activity is in a product, the more free water can be used by microbes as a food source or to support chemical and enzymatic reactions leading the product to spoil. In other words, the higher the water activity value, the more vulnerable cannabis products are to microorganism growth.

Moisture content, however, is the amount of moisture in a product is usually expressed as a percentage of the total. The most common method of moisture content measurement is heating the material to dry it and recording the beginning and ending weights; Known as Loss On Drying. This technique returns the knowledge of the most easily measured moisture. More difficult moisture measurement requires breaking down the substance’s chemistry.

Water Activity and Cannabis

Knowing the water activity in Cannabis is important. Gauging the water activity in a cannabis product is a great way to test how vulnerable the product is to microbial contamination. High levels of water in a product, can be a recipe where water can use microbes as a source of food or to support chemical and enzymatic reactions leading to spoilage.

Water activity is important for analysis for microbial growth, but additionally, solvent reactions and chemical interactions can be affected, damaging the quality of your product. Avoiding “moisture migration” is vital, it affects the constancy of powders or dehydrated products. Moisture migration occurs when moisture in one item, that is meant to be moist then moves to another item, this is meant to be dry- then you end up with the opposite of what you wanted. These interactions not only can damage a bud, but also edibles and topicals.

Rotronic offers a wide range of meters, probes analyzers, handheld devices, and accessories. Here’s one video we think you’ll find helpful:


Stay Dry! Shop Rotronic at Emerald Scientific.

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To Our Friends and Customers,

We recognize that these are unsettling times and we want you to know that the safety and health of our global community, including our valued customers and dedicated vendors, is of the utmost importance to us.

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Ken Snoke
Founder, Emerald Scientific