Bottle defects and their causes
Click the bottle zone where the defect shows and see the likely causes. Each defect says where to look: heating, the blow moulder, the line or the preform itself.
Pearlescence, white haze from stretchingHeating settings
The preform was too cold or overstretched: the material went past its limit and turned white.
Raise heating in that zone, slow the stretch rod, check preform temperature at the infeed.
Milky cloudinessHeating settings
Overheating: PET started to crystallise. Often seen at the base or under the ring.
Lower lamp power in that zone, check oven cooling and ventilation.
Oval or deformed neckBlow moulder
The neck overheated in the oven and lost its shape.
Check the neck shields and neck cooling in the blow moulder oven.
Thick base, thin wallsHeating settings
Material stayed at the bottom: the lower preform zone was heated less than the upper one, or pre-blow started late.
Rebalance heating across oven zones, adjust pre-blow timing.
Gate off centre in the baseBlow moulder
The rod is off axis or the preform is heated unevenly around its circumference.
Check rod alignment and preform rotation in the oven.
Blow-out during blowingPreform
An overheated spot, an inclusion or a bubble in the wall. If blow-outs repeat in one place across a batch, moulding may be the cause.
Check heating. If the batch is the problem, set it aside and send us photos and the batch number.
Bubbles and black specksPreform
A preform moulding defect: moisture in the resin or foreign inclusions.
Set the batch aside and contact the supplier with photos and the batch number.
String on the gatePreform
A moulding defect: a string left when the preform separated from the gate. It can puncture the bottle.
Set the batch aside and tell the supplier.
Leaking capLine and packing
A cap of a different standard, damaged thread or wrong capper settings.
Check the PCO 1881 or PCO 1810 standard, inspect the thread, check the capping torque.
Rocking baseBlow moulder
The base did not cool enough in the mould or was overheated.
Check base mould cooling and heating of the lower preform zone.
Uneven thickness around the bottleHeating settings
The preform is heated unevenly: it does not rotate in the oven or sits close to one lamp.
Check spindle rotation and reflector positions.
Scratches and scuffsLine and packing
Damage in transport, in a crushed box or on the conveyor.
Check packing on delivery and the conveyor guides.
If the preform is the cause
Most bottle defects come from heating and blowing settings rather than the preform. But if a defect repeats in one place across a batch and does not go away after adjustment, set the batch aside and message us with photos of the bottle and preform and the batch number from the box.
