Making a homemade automotive clay bar isn't commonly recommended because the commercial clay bars are specifically engineered with materials designed to safely and effectively remove contaminants from car paint without causing damage.

However, if you're in a pinch or curious about a DIY approach, some people have experimented with various homemade recipes, though they may not be as effective or safe as commercial products.

DIY Clay Bar Alternative

One of the simpler homemade alternatives involves using household materials that can mimic the gentle abrasive properties of a commercial clay bar. Here’s a basic approach:

Materials Needed:

• Fine grade natural modeling clay (available at craft stores)
• Water or a DIY lubricant (like soapy water)

Instructions:

1. Warm the Clay: Knead the modeling clay with your hands until it becomes pliable. This makes it easier to handle and more effective at picking up dirt.

2. Flatten the Clay: Flatten the clay into a small, flat disc that fits comfortably in your hand.

3. Lubricate the Area: Before using the clay on your car, ensure the area is thoroughly washed and still wet, or use a spray bottle to apply a lubricant like soapy water to prevent the clay from sticking to the paint and causing scratches.

4. Gentle Application: Gently glide the clay over the lubricated surface of your car. If the clay sticks or the surface starts to dry, apply more lubricant.

5. Keep It Clean: Fold and knead the clay periodically to expose a clean surface. Be cautious as natural clay can be more prone to leaving residues or breaking apart compared to synthetic detailing clay.

6. Finish Up: After claying, wash the car again to remove any clay residue and follow up with a wax or sealant to protect the paint.

Caution:

• Test First: Always test your DIY clay on a small, inconspicuous area of the car to ensure it doesn’t scratch the paint.
• Limitations: Natural clays may not be as effective at contaminant removal and could potentially be more abrasive than synthetic detailing clays designed for automotive use.
• Frequency: Use this method sparingly to avoid potential paint damage.

While a DIY clay bar can be an interesting experiment, for best results and to ensure the safety of your car's paint, it’s advisable to use commercially available clay bars specifically designed for automotive detailing. These products have been tested to ensure they work effectively without damaging the paint.