During Production Inspection for Ceramics and Pottery in Vietnam: AQL Sampling Explained
- Fiona Li
- Aug 3
- 7 min read
You approved the sample. The factory confirmed your specs. Production is underway somewhere in Vietnam, and you're 10,000 miles away hoping everything goes to plan.
For most home goods importers, that gap between "production started" and "container shipped" is where problems quietly compound. A glaze inconsistency on unit 50 becomes a pattern by unit 500. A wall thickness that's 2mm off tolerance on one piece means the whole batch is out of spec before anyone flags it. By the time you see it in a pre-shipment report, half your order is already packed.
This is exactly the problem that DUPRO, During Production Inspection, exists to solve. And for fragile home goods like pottery, ceramics, and decorative homeware sourced from Vietnam, it's not a nice-to-have. It's the inspection that decides whether you're making a correction or eating a loss.
What Is a DUPRO, and When Does It Happen?
A During Production Inspection (DUPRO) is a quality check conducted while manufacturing is still in progress, typically when 20% to 40% of the order is complete. It's the middle checkpoint in a three-stage QC sequence: after pre-production verification of materials and specs, and before the final pre-shipment inspection (PSI).
The timing is deliberate. At 20–40% completion, enough units exist to assess production consistency, but the factory still has time to correct course without scrapping the batch or delaying the ship date. Catching a defect at this stage is a conversation. Catching the same defect at the PSI is a problem.
For fragile categories like pottery and ceramics, this inspection window matters more than for most product types. According to Ceramics International (Elsevier) (2021), many ceramic defects, including warping, glaze inconsistencies, and firing cracks, are process-driven and originate during forming, glazing, firing, or cooling rather than after production. If your inspector isn't on the factory floor while production is running, those defects can be replicated across hundreds of units before anyone notices.
How to apply AQL in ceramics and pottery production line?
AQL stands for Acceptable Quality Limit, a statistically-based sampling standard defined by ISO 2859-1 that determines how many units to inspect from a production lot and how many defects constitute a failure.
AQL 2.5 for major defects is the standard most consumer goods buyers use for items where a defect would be visible or would impact customer satisfaction, a chipped rim, a glaze run, a dimension that's off enough to affect stacking or packaging. It doesn't mean you're accepting 2.5% defective goods. It means your sampling plan is calibrated to detect a defect rate above that threshold with statistical reliability.
Here's what that looks like in practice: For example, if a purchase order is for 1,200 ceramic planters and approximately 20% of production has been completed, around 240 finished units may be available for inspection. Then:
General Inspection Level II, using AQL 2.5/4.0 → Lot size of 240 pieces → inspector pulls a sample of approximately 32 units at General Inspection Level II
AQL for major defects 2.5 → the batch passes if 2 or fewer major defects are found; fails at 3 or more
AQL for minor defects 4.0 → the batch passes if 3 or fewer major defects are found; fails at 4 or more
For ceramics specifically, major defects typically include cracks, chips, warping beyond tolerance, glaze pinholes on visible surfaces, dimensional deviations outside spec, and color variation beyond an approved range. Minor defects might include small glaze bubbles on non-visible surfaces or minor finish inconsistencies within a defined tolerance band.
The inspector measures item by item, weight, height, diameter, against your approved sample and spec sheet. Not spot-checking. Not eyeballing. Unit by unit, with calipers and a checklist.
Why ceramics and pottery need DUPRO more than most categories?
Not every product category carries the same risk profile during production. Ceramics are particularly unforgiving for a few reasons.
The defect rate in ceramic production is inherently higher. Kiln firing introduces variables that don't exist in other manufacturing processes, temperature consistency across the chamber, moisture content in the clay body, cooling rate. Uneven firing leads to warping, cracking, or pinholes that can't be reworked after the fact. A batch fired at slightly the wrong temperature looks fine until it's in a customer's hands.
Quality drift is faster. In many factory settings, the first production run after sample approval is the best one. Workers are focused, supervisors are attentive, the approved sample is fresh on the bench. By the third week of a six-week run, that discipline can slip. An inline check at 20–30% completion catches drift early.
Spec communication breaks down more easily. When English isn't the factory's first language, written specs for ceramics, glaze finishes, texture descriptions, color references, are particularly prone to interpretation gaps. Your inspector should be comparing physical units against your approved production sample, not just checking a spec sheet. That distinction catches more issues than most buyers realize.
Packaging for fragile goods starts during production. This is the detail most QC guides skip entirely. For pottery and ceramics, packaging method is a quality issue, foam placement, carton wall thickness, inner dividers, void fill. If your team isn't verifying packaging spec while production is running, you'll find out about the problem when breakage claims come in after delivery.
What actually gets checked during an inline inspection for home goods
A well-run DUPRO for fragile ceramics and homeware covers more ground than a simple defect count. Here's what your inspector should be verifying:
Production conformance
Dimensions (height, diameter, wall thickness) measured against approved sample with calipers
Weight variance within acceptable range
Glaze application: coverage, finish consistency, color match to approved reference
Surface defects: cracks, chips, pinholes, warping, rough spots
Functional specs: stability on a flat surface, lid fit, handle attachment strength (where applicable)
Workmanship consistency
Are the first 20% of units consistent with each other, or is there variation batch to batch?
Is the factory using the correct materials and components per your BOM?
Are process controls in place on the line (QC sign-off per X units, measurement logs)?
Packaging spec compliance
Is foam density and placement matching your packaging spec?
Are inner dividers present and correctly positioned for fragile separation?
Is the carton wall thickness meeting your freight requirement?
Are outer carton labels, barcodes, and country-of-origin marks correct?
Production status
Is the factory on schedule to meet your requested delivery?
Is there any sign of subcontracting to a third facility?
How inline inspection works for your specific product category?
We're happy to walk through your production situation.
The Real Cost of Skipping DUPRO
Most importers who skip inline inspection do it for one of three reasons: cost, timeline, or the assumption that the factory "did fine last time." All three are understandable. None of them survive contact with a failed shipment.
A single DUPRO inspection typically costs $250–$400 for a third-party service provider. A container of fragile goods with a 15% breakage rate or a glaze defect across 40% of units is a different number entirely, one that includes rework costs, re-shipment, customer credits, and the delay of a product that was supposed to be on shelves.
According to Hauck, Z. et al. (2022), when defects are caught during production rather than post-shipment, the factory still has the ability to adjust process and correct remaining units. After the container is sealed, that option is gone.
Does DUPRO Replace the Pre-Shipment Inspection?
No. They serve different functions and catch different things.
DUPRO catches process problems, defects that are happening on the line and will compound across the batch if not corrected. It's the intervention.
The Pre-Shipment Inspection (PSI) is the final gate, a random AQL sample of finished, packed goods to confirm the batch meets your standards before payment release and container loading. For fragile home goods, both checkpoints are necessary.
Skipping DUPRO and relying only on PSI is the equivalent of skipping all medical checkups and hoping the annual physical catches everything. Sometimes it does. Often, by then, the problem is more expensive to fix.
Managing DUPRO in Vietnam with an In-Country Quality Team
The logistical challenge for many US importers isn't whether to do DUPRO, it's how. Coordinating a third-party inspector across time zones, managing the schedule with the factory, reviewing reports in a language gap, and deciding what to do with a marginal result all require bandwidth that most small and mid-size brands don't have.
Having an in-country operations team that manages both the supplier relationship and the inspection schedule changes that dynamic. The team that approved the sample and negotiated your order is also the team walking the factory floor at 20% completion, with the approved sample in hand, measuring unit by unit, and flagging issues in the same conversation where they can be resolved.
That's the difference between a report that arrives three days later and a correction that happens the same day.
If you're sourcing ceramics, pottery, or fragile homeware from Vietnam and want to understand how inline quality control fits into your production process, our QA/QC team works directly on the factory floor, not through a third-party booking platform. You can also learn more about how we manage supplier relationships and production oversight from pre-production through delivery.
Quick Reference: DUPRO Checklist for Fragile Home Goods
Checkpoint | What to Verify |
Timing | 20–40% of production complete |
Sampling method | AQL 2.5 major / 4.0 minor, General Level II |
Dimensions | Measure against approved pre-production sample |
Surface quality | Glaze, cracks, chips, pinholes, warping |
Color/finish | Compare to approved pre-production sample |
Packaging | Foam placement, dividers, drop test, carton spec |
Labels | Barcode, country of origin, shipping marks |
Production status | On schedule, no unauthorized subcontracting |
How inline inspection works for your specific product category?
We're happy to walk through your production situation.
