Checklist for Approving Tile Samples Before Bulk Production

Why Sample Approval Fails in Production

Sample approval is not just a formality. It is the control point where the specification meets the factory floor. When a project moves from sample stage to bulk production, the factory shifts its line setup, raw material batches, and firing parameters. Small changes during that transition cause visible defects.

The failure usually starts with a missing baseline. A buyer signs off on a box of tiles in a showroom but never records the exact measurements, glaze batch, or lot number. Months later, the production shipment arrives, and the color is slightly darker or the size is a few millimeters out of tolerance. The factory claims the new tiles match the original samples. The buyer has no proof otherwise.

This process exists to prevent that gap. It creates a physical and written record that the factory must match.

What to Measure Before Signing Off

The first step is physical measurement. Do not rely on visual inspection alone. Tile dimensions vary by batch, and small differences accumulate into installation problems.

Use a digital caliper to measure length and width. Check at least three tiles from different corners of the sample box. Record the average and the maximum deviation. If the specification allows for a tolerance of plus or minus 0.5 mm, note whether the samples sit within that range.

Check thickness as well. For porcelain tiles, thickness consistency is critical for flatness and edge-to-edge installation. A variation of even 0.2 mm across the sample set can indicate inconsistent pressing.

Also inspect the edges. Look for chipping, rounding, or uneven glaze lines. A clean, square edge suggests proper cutting and firing. A rounded or chipped edge may indicate a problem in the raw material or the firing schedule.

Measurement	Tool	Action
Length and Width	Digital caliper	Measure three tiles and record the average
Thickness	Digital caliper	Check for variation across the sample set
Flatness	Straight edge	Look for warp or bow in each tile
Edge Quality	Visual inspection	Check for chips and uneven glaze lines

How to Check Color and Glaze

Color approval is the most common source of dispute. Human eyes adapt quickly to a single light source, making it easy to miss subtle shifts.

Display the sample tiles under at least two types of lighting. Use a neutral white light source with a color temperature of around 5000 Kelvin, which is common in industrial settings. If available, also view them under a warmer light, around 2700 Kelvin, which mimics many residential environments.

View the tiles from different angles. Glaze reflectivity changes with viewing angle. A tile that looks matte from the front may show a slight sheen from the side. This is known as the angle of reflection. Note the level of gloss and whether the surface texture is consistent.

Check for color consistency across the sample set. Lay the tiles in a grid and look for variation. A single tile that is noticeably lighter or darker than the rest is a red flag. It suggests uneven glaze application or a firing issue.

Look for pinholes, crawling, or pinning. These are glaze defects that appear as tiny bubbles or dark spots on the surface. They are often acceptable in small quantities but indicate a problem in the glaze batch if they appear frequently.

What to Verify About Material Identity

A sample must match the material description in the purchase order. This is where substitution errors happen.

Check the sample for the correct body material. Porcelain tiles are typically dense and ring-like when tapped. Ceramic tiles are softer and may sound duller. If the order specifies a specific clay body, such as a high-alumina porcelain, ask the supplier for the material data sheet.

Verify the glaze type. Is it matte, satin, or gloss? Is it an unglazed back for adhesion? For unglazed backs, check the texture. It should be consistent and free of dust or debris.

Confirm the lot or batch number if it is present. Some suppliers mark their tiles with a code that corresponds to the production run. This helps you track the specific materials used.

Ask for the sample to be clearly labeled. The label should include the product name, the color code, the size, and the date of the sample. This label must match the label on the production shipment.

Red Flags That Should Stop Approval

Not every variation is acceptable. Some issues are immediate red flags that should stop the approval process.

If the samples show a visible color difference between the first and last tile in the box, do not sign off. This suggests the glaze was applied unevenly or the kiln temperature fluctuated during firing.

If the dimensions are outside the agreed tolerance, reject the sample. A tile that is 1 mm larger than the specification will not fit with the others, and the grout lines will look uneven.

If the glaze has a visible defect, such as a large pinhole or a patch of crawling, do not approve. This indicates a problem in the glaze preparation or the firing process.

If the sample does not match the purchase order description, stop. Do not assume the factory will correct the material for bulk production. The sample is the baseline. If it is wrong, the bulk run will be wrong.

How to Document and Store the Approved Sample

The approval is only as good as the record. A signed paper is not enough. You need a clear, dated, and specific document.

Create a sample approval form. It should include the date, the sample reference number, the product name, the color code, and the size. Include the measured dimensions and the maximum deviation found. Describe the glaze finish and any acceptable variations.

Have both parties sign the form. Your representative and the supplier’s quality representative should both sign. This creates a mutual agreement on what is acceptable.

Store the approved sample in a controlled environment. Keep it in a box, away from direct sunlight and heat. Do not display it in a bright office or a warehouse with high temperature fluctuations. Light and heat can fade or alter the glaze over time, changing the reference point.

Keep the stored sample for the duration of the project and for a period after the final shipment. This allows you to compare late arrivals against the original reference.

How to Use the Approved Sample in Production

Once the sample is approved, it becomes the reference standard for the entire project.

Send the approved sample, or a copy of the approval form, to the factory. Ask them to use it to calibrate their firing and glazing lines.

Request a pre-production inspection. Before the full bulk run begins, the factory should produce a small batch and send it for inspection. This batch should be compared against the approved sample.

If the pre-production batch matches the sample, allow the bulk run to proceed. If it does not match, stop the production. It is cheaper to correct the process now than to reject thousands of tiles later.

Keep the approved sample safe. Do not lend it to others. Do not use it for testing or cutting. It must remain intact and unaltered until the project is complete.

How to Handle Disputes After Production

Even with a strong approval process, disputes can occur. If the production shipment does not match the approved sample, refer to the sample approval form.

The form should state the exact dimensions, the glaze finish, and the color reference. If the shipment deviates from these recorded values, you have a documented basis for rejection.

Photograph the shipment before unloading. Take clear photos of the tiles, the labels, and any defects. Compare the photos to the approved sample.

Contact the supplier immediately. Do not install the tiles. Once they are on the floor, the cost of removal and replacement becomes a major expense.

Ask for a corrective action plan. The supplier should explain how the deviation occurred and how they will prevent it in future batches.