In our experience we have yet to find a mud we didn’t like—to use in building. We have used rocky, sandy Rocky Mountain mud to dark, sticky Bangkok mud. All that is necessary is that your subsoil has some clay content. Yours may have a bit too much clay or sand and you can adjust for this. There is a wide range of mud that is usable without any adjustments. Here are a few ways to check yours:
- Mix some subsoil with water and kneed with your hand until your hand gets good and muddy. Dip in water and bring up without rubbing at all. If you still have mud on your hand, you have enough clay. If your hand comes out clean you have too much sand and need more clay. If your hand comes out real sticky muddy and you have to scrub to get it off, you have too much clay and need to add some sand.
- Mix subsoil with water and make to sculpting consistency. Make a thick worm the size of your finger. Hold it out and if it can hold shape you have enough clay. If it is real sticky and does not break when held sideways for a while you may have too much clay.
- Soak 1 tablespoon subsoil, one cup of water and one teaspoon salt for a few minutes. The layers in your soil will separate. On the bottom will be rocks and heavy debris. Next will be rough sand, then fine sand. Above that will be clay and then on top silt. From this test you will be able to find the percentage clay you have in your soil. You will need at least 15% clay including silt to make good bricks. More than 50% is too sticky and you will need to add more sand.