Research Protocol

Quantifying the Green Color of Dried Ground Tea Leaves

Authors: Jessica Weaver and Carol Miles 
Affiliation: Washington State University Northwestern Washington Research and Extension Center

_{September 2026} 

Introduction 

Green tea is well known for its bright green leaf color, and the color of ground green tea leaves can be a sign of high-quality tea. This guide illustrates how to quantify the green color of dried ground tea leaves using photographs analyzed with ImageJ (Fig. 1).

Supplies 

• 2 tripod small light panels – for keeping the lighting consistent between samples, e.g.:
  • BP66, Shenzhen Neewer Technology, Luohu District, Shenzhen, Guangdong Province, China
• White background – we use a white cutting board to provide contrast
• Color grade scale – to enable comparison of photos, e.g.:
  • A-6106CS, Arrowhead Forensics, Lenexa, KS
• Clear plastic petri dish – to contain the ground tea and keep the analysis area consistent
  • 351029, Falcon, Corning, NY
• Tripod – to stabilize the camera and keep image dimensions consistent, e.g.:
  • O234A1, K&F Concept, Shenzhen, Guangdong Province, China
• Spice grinder – to grind whole leaves into a powder, e.g.:
  • WSG30, Waring Commercial, Stamford, CT
• Phone camera – to capture images
• Computer with ImageJ software – to quantify green color
  • Available for free at ImageJ
• Dried green tea leaves

Experimental Set Up

1. Place the white background on a flat work surface.
2. Set up two lights on either side of the cutting board with the feet of the lights touching the sides of the cutting board, height 72 cm to the top of the light and an angle of 90 degrees (Fig. 2).

3. Place tripod behind cutting board with two of the feet touching the cutting board; height 67 cm to the top of the tripod and 90 degree angle (Fig. 3).

4. Place the color grading scale on the white background.
5. Grind leaves into powder.
6. Place the powder into the top of a petri dish (Fig. 4).

7. Place the petri dish top onto the cutting board.
8. Using the bottom of the petri dish, press the ground tea into a flat layer (Fig. 5).

Figure 5. The process of pressing the ground tea leaves into a flat layer.

9. Remove the petri dish bottom and take a photo of the ground tea (Fig. 6).

Image Analysis

10. Upload photos to the computer.
11. Download, rename photos using the following format: time_treatment_leaves_rep eg;
    • 5min_soak_top3_rep3.jpg
12. Crop photos (Fig. 7).

13. Open your first photo in ImageJ by clicking on “File” –> “Open” and select the photo you want to start with.
14. Click on the circular selection tool and circle the grounds inside of the petri dish (Fig. 8).

15. Click “Analyze” -> “Histogram” (Fig. 9).
16. Click “RGB” until the histogram is measuring green values (Fig. 10).

17. Write down the mean value for the sample image, the higher the value the greener the sample.
    • In this case the tea grounds mean value measured 166.145