I did a comparison of different soils I could buy locally and also my own soil. After screening soil to get out the big lumps, I filled a glass jar approximately 2/3 with soil and the rest with water and shook it for about a minute. After a day, you can see how each one looked. Theoretically, I should see sand, silt and clay. For loam, the mixture should be 40% sand, 40% silt and 20% clay.
I found this site with instruction on this test. Here’s their basic instructions.
- Clean the soil of rocks and large pieces.
- Let the soil dry and pulverize it.
- Fill a tall, slender jar (like a quart canning jar) 1/4 full of soil. Add water until the just is 3/4 full and then add a teaspoon of dishwasher detergent.
- Put on a tight fitting lid and shake hard for 10 to 15 minutes.
- Set the jar where it will not be disturbed for 2-3 days.
- After 1 minute, mark on the jar the depth of the sand.
- After 2 hours, mark on the jar the depth of the silt.
- When the water clears mark on the jar the clay level. This typically takes 1 to 3 days.