Proper usage guidelines for fused quartz include:

1. Handling: When handling fused quartz, it is important to wear clean, lint-free gloves to avoid contamination. Handle the material gently to prevent any scratches or damage. Avoid direct contact with bare hands, as oils and sweat can leave residues on the surface.

2. Cleaning: Fused quartz can be cleaned using mild detergents or solvents, followed by rinsing with deionized water. Avoid using abrasive cleaners or scrubbing brushes that can scratch the surface. It is recommended to use lint-free, non-metallic materials for cleaning, such as soft cloths or brushes made of natural fibers.

3. Thermal Shock: Fused quartz has excellent thermal properties, but it can still be susceptible to thermal shock. Avoid rapid temperature changes, especially from extreme hot to cold or vice versa, as this can cause cracking or breakage. Gradual heating or cooling is recommended to minimize thermal stress.

4. Chemical Resistance: Fused quartz is highly resistant to most chemicals, but it can still be affected by certain aggressive substances. Avoid prolonged exposure to strong acids, alkalis, or oxidizing agents, as they can degrade the material. If contact with such chemicals is unavoidable, rinse the surface thoroughly with water afterwards.

5. Optics Handling: If using fused quartz for optical applications, take extra care to avoid fingerprints, dust, or scratches on the surface. Use clean, lint-free gloves and handle the optics by the edges or non-optical surfaces whenever possible. Store optics in protective cases or clean, dust-free environments.

6. Machining and Fabrication: Fused quartz can be machined and fabricated using diamond tools or abrasive techniques. However, it is important to use proper cooling and lubrication to prevent overheating and thermal stress. Follow recommended machining parameters and consult with experts or manufacturers for specific guidelines.

Always refer to the manufacturer's instructions and guidelines for the specific fused quartz product being used, as different grades and forms may have specific usage recommendations.