Color of Bulk Distillate : Why is it so dark?

When buying cannabinoid products in bulk,  you will often find yourself thinking about the color. Color can be an important indicator of quality in some cases. No one has any desire to consume a concentrated black tar. Color is not the only indicator of purity though. Test results from a certified lab should do most of the talking. Here is some background and some advice for those producing/buying bulk THC or CBD distillate.

Beer-Lambert Law

To break this down quick and dirty, you need to focus on three of the letters. A, C, and L.

A = B * C * L

Where:

  • A is the absorbance. You can think about this as a measurement of light blocked.
  • B is a property of the compound using a specific color
  • C is the concentration of the compound
  • L is the path length or total distance light travels through this substance.

The gist of this equation is that there are ways to change the color and appearance of substances! They may seem so obvious that it is easy to not even think about them.

The first method is to change the concentration of the substance. If there is a higher “density” of a compound, the more light it will absorb. The example here is that if you dissolve crude at a ratio of 1:1 in a solvent, that will look different that something at a ratio of 10:1. Simple enough. The second is to change the path length. You can think of this like a viewing distance. Even crystal clear water blocks tons of light just a few feet below the surface. Again, if you are looking through more of something, more light will be blocked.

This is great! Now you understand over 75% of how a UV-Vis spectrometer works. Specific colors of light interact with certain chemicals in a predictable and reproducible way.

Take Away

The point being that in say a vape cartridge, an oil may look light. In bulk however, the color is often much more apparent. When buying and selling distillate, it is important to consider the bulk appearance versus in a small container. Does the oil look clear and have very little color even in a large jar? Then the quality is likely very good. As always however, the CoA or ‘certificate of analysis‘ speaks for itself. Very high potency distillate (95%+) can have strong color. It will generally still have good clarity though, meaning there will not be streaks or other contaminants in your product.

Bulk distillate versus small batch appearance comparison
The same oil in two different volumes. Now imagine how light the color would be in a vape cartridge!

While training new users on spinning band distillation systems, I say that you can expect the color of the “side-arm” to be a good indication of what a vape cartridge will look like once filled. Always remember that of course lighting has a lot to do with appearance and so does the backdrop.

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