Solving Scratches

Understanding scratches

Scratches are linear grooves that appear on the surface of a stone, usually caused by abrasive particles used in the grinding process. These flaws not only affect the beauty of the stone, but also impair its functionality, so timely and effective treatment is crucial.

Reason for scratches:

• Abrasive particles: Using unsuitable or abrasive abrasive materials can introduce larger particles which can cause scratches.
• Inconsistent grinding: Uneven pressure or inconsistent grinding technique can cause different wear patterns, which can create scratches.
• Contaminants: Particles left over from previous grinding steps can scratch the surface if not cleaned properly.

Solutions for preventing and removing scratches

1. Ensure uniformity after rough grinding:

• Inspection: After the rough grinding stage, check the surface of the stone sample to confirm that the wear marks are uniform and consistent. This step is essential to prevent scratches in the subsequent polishing stage.
• Re-sand if necessary: If you notice inconsistencies, repeat the rough sanding process to ensure a smooth and even base surface. This will help to minimise the risk of scratches later on.

2. Thorough cleaning between steps:

• Remove abrasive particles: After each grinding or polishing, clean the stone surface and the specimen holder thoroughly. This removes any larger abrasive particles that may have accumulated and prevent them from causing scratches in the next stage.
• Use an appropriate cleaning solution: Use a soft brush and a neutral pH cleaner to ensure the surface is free of contaminants before proceeding to the next step.

3. Adjust grinding and polishing time:

• Increase preparation time: If scratches are still visible during polishing, consider increasing sample preparation time by 25% to 50%. The additional time can improve polishing efficiency and help achieve a smoother surface.
• Pay attention to pressure and speed: Maintain constant pressure and speed during polishing to ensure even treatment of the entire surface. Avoid excessive pressure, which will aggravate scratching.

4. Use the right tools and materials:

• Choose the right abrasive: Choose a diamond grinding disc that is suitable for your specific polishing stone. Make sure the abrasive is in good condition and not worn, as worn tools may cause scratches.
• Fine grit for final polish: Use finer grit materials during the final polishing stage to minimize the risk of scratches and improve the overall result.

5. Zoom in and check:

Quality control: After polishing, check the surface with a magnifying glass (e.g. 200x) to check if there are any remaining scratches. This step helps to take immediate corrective measures if necessary.

Solving False Color

Understanding false colors

False color usually appears as discoloration or stains on the stone surface, which is especially obvious under a magnifying glass. This problem is usually caused by the following factors:

• Pollution: Foreign matter such as oil, chemicals or dust can penetrate the surface of the stone and cause staining.
• Gaps in the resin: If gaps exist between the resin used in the polishing process and the stone sample, these gaps may trap contaminants and cause discoloration.
• Improper sealing: Inadequate sealing between the resin and the stone can allow foreign matter to enter, exacerbating staining issues.

Strategies for dealing with false colors

To effectively address and prevent false color during polishing and grinding, consider the following strategies:

1. Clean the gap:

• Thorough cleaning: Make sure to thoroughly clean all gaps between the resin and the stone sample. Use a suitable cleaner to remove any remaining contaminants that may cause staining.
• Inspect: Check the gap regularly to ensure it remains clean and free of debris.

2. Improve sealing:

• Enhanced sealing technology: Use high-quality sealing materials to tightly bond the resin to the stone. This helps prevent foreign matter from entering the gaps and causing stains.
• Application method: During installation, ensure that the resin is spread evenly and tightly to avoid leaving any gaps.

3. Choose the right resin:

• Material selection: Choose a resin that matches the characteristics of your stone sample. The right resin can significantly reduce the risk of staining and improve the overall effect.
• Consult: If you are unsure, consult your supplier or an expert to find the best resin for your specific stone type.

4. Clean thoroughly after each treatment:

• Post-preparation cleaning: After each sample preparation step, clean and dry the sample thoroughly. This practice helps prevent the accumulation of contamination and staining issues.
• Rinse immediately: Within 10 seconds after oxide polishing, rinse the polishing cloth with cold water to ensure that both the sample and the polishing cloth are free of contaminants.

5. Avoid using compressed air containing contaminants:

Drying tips: After final polishing, avoid using compressed air that may contain oil or water to dry the sample. Instead, use a clean, dry cloth to gently wipe the surface.

6. Proper storage:

• Dry environment: Store polished samples in a dry environment to prevent moisture accumulation which can cause corrosion and staining.
• Use a dry tray: It is recommended to place the sample in a dry tray or container to protect it from exposure to air and moisture.

Solving the Problem of Smooth Edges

Understanding edge rounding

Edge rounding occurs when the edges of a stone sample are chamfered or rounded during the polishing process. This phenomenon is particularly noticeable when using a high-resilience polishing cloth, which can grind both the surface and the edge of the sample. The main causes of edge rounding include:

• Difference in wear rate: When the wear rate of the polishing resin exceeds the wear rate of the stone sample, it causes uneven grinding, resulting in rounded edges.
• Gap between resin and sample: If there is a gap between the resin and the stone, the edge may become chamfered due to over-grinding.
• Material characteristics: Certain materials, such as stainless steel, are more susceptible to edge rounding, especially when viewed under high magnification (e.g. 500x).

Strategies for dealing with rounded edges

To effectively address edge rounding, consider the following strategies:

1. Protect the edge:

• Handle with care: When working on a gemstone, be extra careful to protect the edges that need to be inspected. This will help prevent chamfers from over-polishing.
• Positioning: When polishing, ensure that the side of the sample that needs to be protected faces backwards and the side that does not need to be protected faces forwards. This positioning minimizes the risk of edge rounding.

2. Polishing technology:

• Polishing direction: Polish against the direction of the polishing disc's rotation. This method helps reduce the possibility of edge rounding.
• Center: Position the sample as close to the center of the polishing disc as possible. This positioning allows for better control of polishing and reduces the risk of excessive wear on the edges.

3. Control polishing time:

Time management: Monitor and control the polishing time to avoid the edge being exposed to the polishing cloth for too long. Polishing for too long will aggravate the edge rounding effect.

4. Adjust polishing material:

• Choose the right material: Choose a polishing material that matches the wear rate of the stone being polished. This helps ensure even wear on the edges and surfaces.
• Use different resins: Consider using resins of different hardnesses to balance the wear rate between the resin and the stone sample.

5. Monitoring material peeling:

Observe for inconsistencies: Due to differences in wear rates and hardness at different stages of the material, monitor the material removal for any inconsistencies. This observation helps identify areas that may need additional attention during polishing.