How to Prevent Suction Cup Marks on Glass

Reducing suction cup marks starts with understanding the glass surface and the complete handling process. Confirm the glass product, the contacted side and the manufacturer's processing requirements before changing a suction cup or adding a protective cover. Evaluate surface quality and holding performance together under the intended operating conditions.

If marks are already present, first record the contact pattern and operating conditions.

Confirm the Glass Product and Contact Side

Record the glass manufacturer's product name, coating, processing stage and contacted surface. For coated glass, check whether contact with that surface is permitted and whether specific contact materials or protective measures are required.

Follow the instructions for the exact glass product and the region where it was supplied. Guidance for one coating or market does not establish the requirements for every glass product.

What Glass Processing Guidelines Say

The documents below address specific glass products and handling conditions. Some name an MTC cover; others describe general requirements for contact materials or protective covers. Check the applicable document for the exact glass product and region before selecting a configuration.

Documents That Name MTC Covers

General Contact and Protective-Cover Requirements

The following documents describe handling requirements for their listed products. They are not presented here as MTC-specific recommendations.

The Guardian, AGC and TIMELESS summaries were last reviewed on 13 October 2026. Confirm the current requirements for the actual glass product and region with its manufacturer.

Review the Entire Contact Path

Map the surfaces that touch the glass from loading through the relevant downstream processes. Include suction cups, covers, gloves, rollers, belts, separating pads and cleaning equipment.

For each contact point, record:

• The glass side being contacted.
• The condition and cleanliness of the contacting material.
• Any sliding or relative movement.
• When the glass is inspected and when a mark is first observed.
• Changes in materials, cleaning methods or equipment settings.

Keep observations separate from conclusions. A mark first noticed after washing or heat treatment may have become easier to see; that observation alone does not identify when or where it formed.

For contact with conveyor rollers, review roller contact protection and MTC-ROLL covers alongside the glass manufacturer's requirements for the contacted side.

Choose a Surface Protection Approach

Possible actions include controlling contamination, correcting contact motion, replacing a worn cup, reviewing the cup compound or evaluating a separate protective contact layer. Choose an approach based on the observed problem and the glass manufacturer's requirements.

Compare suction cup covers and non-marking suction cups when considering the two approaches.

MTC suction cup covers provide an intermediate contact layer over a suitable suction cup. If a cover is appropriate for the application, use the MTC cover selector to find a candidate size. A dimensional match still requires checks of the cup profile, cover retention and operating conditions.

Record Surface Observations Before and After Handling

A useful surface record identifies what was inspected, under which conditions and at which stage. Agree on the inspection method and acceptance criteria with the customer's responsible quality or engineering personnel before comparing configurations. Follow the applicable glass manufacturer's requirements.

1. Identify the sample and contact surface

   Record the glass manufacturer, exact product, coating or surface treatment, contacted side, processing stage and sample reference. Link the record to the cup and cover configuration being evaluated.

2. Establish the baseline

   Inspect the relevant area before the evaluated contact and record any existing pattern, residue or damage. Keep photographs where available. If an earlier inspection is unavailable, record this limitation rather than assuming the surface was clear.

3. Keep inspection conditions consistent

   Use the agreed lighting, background, viewing position and surface condition before and after handling. For photographs, keep the method consistent and identify the same sample and contact area. Record any changes to these conditions.

4. Record the relevant process stages

   Document the result after handling and, where included in the agreed evaluation, after washing or another downstream process. Describe the visible appearance and location. Record the inspection stage, date, inspector and photo references.

Keep additional diagnostic observations separate from the agreed acceptance inspection. A close-up taken to investigate a pattern serves a different purpose from a formal acceptance check. Record the conditions used for each.

For example, a record might state: “Ring-shaped pattern at the recorded cup position after handling.” If supported by the inspection, it might state: “No discernible contact pattern was observed on the listed sample under the stated inspection conditions.” Include the sample, stage and supporting records with either statement. A ring-shaped pattern alone does not establish a cause. A result recorded under specific conditions does not establish the outcome for other glass products or operating conditions.

This is EUROTECH's suggested recording framework. It does not set universal defect limits or replace the applicable glass specification and agreed acceptance procedure.

Validate the Covered Configuration

Use a configuration and application trial record to document the proposed combination and its results, including the surface observations described above.

1. Before the trial: Identify the glass, cup, cover, equipment and intended operating range. The responsible engineering personnel should establish the trial method, permitted comparison configuration and acceptance criteria. Do not test an uncovered cup on a coating where that contact is not permitted.
2. During the trial: Record the actual configuration, vacuum conditions, relevant measurements, relative movement, cover retention and surface observations. Document deviations. Keep selector assumptions separate from measured operating data, and include checks after relevant downstream processes where these form part of the agreed evaluation.
3. After the trial: Review handling performance, surface quality and process suitability separately. State the conditions covered by the decision, unresolved items and changes that require further review. A favourable surface result does not establish adequate holding performance.

Record Separate Results Before Making an Adoption Decision

• Surface quality: State whether the sample met the agreed surface criteria under the recorded inspection conditions.
• Holding performance: Record the engineering assessment for the actual configuration and operating range, with the supporting measurements and observations.
• Process suitability: Review installation, downstream processing, inspection and maintenance requirements for the intended use.

Record each result as Met the agreed criteria, Did not meet the agreed criteria or Incomplete, with its supporting evidence. Use “Incomplete” when required information, observations or measurements are missing.

The customer's authorised engineering or process representative should approve use only when all applicable criteria have been met for the stated scope. Record the glass products, configurations and operating conditions covered by the decision. A configuration with failed or incomplete holding-performance results requires further engineering review before adoption.

The configuration and trial record helps organise this evidence. It does not provide a rated working load or automatic approval to lift. Request a blank record or an MTC application review.

Maintain the Evaluated Configuration

Include the cover and the underlying cup in inspection and maintenance arrangements. Follow the applicable product instructions for cleaning and replacement. A contaminated or damaged cover requires review before further use.

Review changes to the glass, contact side, cup, cover, load, motion, vacuum conditions or cleaning process against the conditions already evaluated. The responsible engineering personnel should decide whether further checks or testing are needed.

For protecting cups while they are not in use, see SSUZ suction cup storage covers.

Frequently Asked Questions

Will a suction cup cover eliminate every mark?

The result depends on the actual surface, contact materials, cleanliness and process. Record the outcome under stated inspection conditions rather than treating a general product description as a guarantee.

Can I keep the original cup load rating after adding a cover?

Do not assume it remains applicable. Review holding performance for the covered configuration, including the load direction and operating cycle. The cited Guardian and AGC instructions warn of reduced handling capacity with protective covers.

Should I use a general cleaning recipe on coated glass?

Follow the glass manufacturer's instructions for the exact product. Do not assume an abrasive method, solvent or general glass cleaner is suitable for every coating. Record any treatment already used when requesting an application review.

How should I begin an MTC application review?

Share the glass product, contacted side, cup details, movement sequence and available observations with EUROTECH. Include the selector result if you have already identified a candidate size.

Request an MTC application review