Oh OK here is the answer as none replied it is acidic because it's pH value is closer to 5 indicating an acid that is the reason coffee are acidic

The Answer to the Riddle: Coffee as an Acid or Base

Introduction:
The riddle presents us with a question: whether coffee is an acid or a base. We are required to determine the answer without any direct test, solely relying on its taste.

Understanding Acids and Bases:
Before delving into the answer, let's first understand what acids and bases are. Acids are substances that release hydrogen ions (H+) when dissolved in water, while bases release hydroxide ions (OH-). The pH scale is used to measure the acidity or basicity of a substance, ranging from 0 (most acidic) to 14 (most basic), with 7 being neutral.

Examining the Properties of Coffee:
To determine whether coffee is an acid or a base, we need to analyze its properties.

1. Color:
Coffee is brown in color. However, the color alone doesn't provide any conclusive evidence regarding its acidity or basicity.

2. Taste:
The riddle states that coffee is bitter in taste. Bitterness is often associated with basic substances rather than acidic ones. Therefore, the taste of coffee suggests it might be a base.

3. Testing the pH:
To validate our assumption, we can conduct a simple pH test. However, since the riddle prohibits direct testing, we need to rely on our knowledge of coffee's taste.

Conclusion:
Based on the information provided, we can infer that coffee is likely a base. The bitter taste of coffee aligns with the characteristics of bases, which release hydroxide ions (OH-) in water. The riddle challenges us to determine the answer without conducting a direct test, and the taste of coffee serves as a clue to its basic nature.

Note: It's important to mention that this answer is based on the given information and assumptions made using general knowledge. For a definitive answer, a pH test should be conducted.