\”Good quality\” means nothing as a contractual standard. Without written definitions, a dispute about quality becomes an argument about intent. This article sets out the specific defect classifications used for pressed glass so you can put numbers in your purchase order.
Define defect categories and acceptable limits
Every inspection standard divides defects into categories with numeric limits. A workable version for pressed glass candle jars:
Critical defects
Not acceptable in any quantity, because they make the product unsellable or unsafe:
- Cracks or chips on the body or rim
- Broken or cracked base
- Sharp edges or points that would cut a user
- Foreign bodies sealed inside the glass
- Fire or burn marks from improper annealing
Major defects
Affect appearance or function in a way a retail buyer would reject. A typical allowance is under 3% of the shipment:
- Visible bubbles larger than a stated diameter
- Noticeable wall thickness variation beyond tolerance
- Colour unevenness beyond the approved reference
- Decoration misalignment, incomplete coverage or off-register printing
- Surface scuffs and scratches visible under normal lighting
- Neck or rim dimensions outside tolerance, affecting lid fit
Minor defects
Cosmetic, generally acceptable in modest quantity:
- Minor surface waves inherent to pressed glass
- Very small bubbles within stated size limits
- Slight colour variation within an agreed band
Functional tests
For candle jars specifically:
- Thermal shock. Test a sample by moving filled jars between temperature extremes. Failure means wall thickness or annealing is inadequate.
- Capacity verification. Verify actual usable volume against specification on a random sample.
- Weight verification. Check piece weight against the agreed tolerance.
- Stability. Confirm the base sits flat without rocking on a flat surface.
- Lid fit. If lids are supplied, confirm thread or rim engagement.
Inspection levels
| Level | When to use | Covers |
|---|---|---|
| Pre-production | Before opening any mould or starting a custom run | Material, dimensions, colour standard, artwork proof |
| During production | Custom or high-risk orders | Early detection before the whole batch is completed |
| Pre-shipment | All orders | Full AQL inspection before the container is sealed |
| Loading supervision | High-value or first orders | Confirms the correct goods and quantities are loaded, and that packing is correct |
For a first order with a new supplier, pre-production and pre-shipment inspection are worth paying for. The cost is small relative to the value of catching a problem before it ships.
Write the standard into the purchase order
Attach the inspection standard as a document referenced in the purchase order, containing:
- Defect categories and the numeric limit for each
- AQL level, usually 2.5 for general inspection
- Approved sample references, signed and dated by both parties
- Measurement tolerances on dimensions and weight
- Test requirements for thermal shock and any market-specific testing
- What happens if the shipment fails: rework, replacement, discount, or rejection
- Who pays for a re-inspection after rework
Without a written failure procedure, passing the inspection is the only thing that matters and you have no leverage if it fails.
The role of the approved sample
One signed, dated physical sample is the most valuable quality document you can hold. It defines colour, finish, decoration placement, wall appearance and overall standard in a way no written description matches.
Keep it. Do not let it get lost in production. When a dispute arises, the approved sample is what everyone refers back to.
On arrival
Inspect a sample on arrival, not the whole container. Draw cartons from the top, bottom and middle of the load. If the failure rate is materially above what the inspection reported, document it with photographs before opening more cartons, and notify the supplier within the contractual claim period. Delayed claims are frequently rejected on procedural grounds alone.
Tell us the defect categories that matter most to your business and we will confirm what our production process delivers. Discuss your requirements with us.