PET bottle laser coding

Permanent date and batch codes on PET bottles.

CO₂ laser can create a clean frosted mark on compatible PET without ink. Bottle formulation, wall thickness, colour, movement and line speed determine the finished code.

Short answer: 9.3 µm CO₂ laser is commonly assessed for PET bottle coding because it can produce a light frosted mark. The process must be tested to achieve contrast without unacceptable distortion or weakening.

What can be marked on PET?

Typical content includes use-by or best-before dates, batch and lot codes, production times, line identifiers, serial data, QR codes and Data Matrix codes. Available marking time falls as speed and code complexity increase.

The key application variables

Resin and additives: bottle formulation and recycled content affect absorption.
Colour and background: clear, tinted and sleeved bottles create different contrast conditions.
Wall thickness: thin areas require careful energy control.
Product stability: rotation, vibration and spacing affect character shape.
Moisture: condensation and line washdown conditions must be considered.
Speed: code content and production rate set the available marking time.

Why 9.3 µm is often considered

PET absorbs 9.3 µm energy differently from the common 10.6 µm wavelength, which can support a more controlled frosted response. It is not an automatic selection: the finished container and required code still need testing. Read the wavelength guide for context.

Proving the code before installation

Trials should use current bottles and include colour or supplier variants. Assess readability, permanence, appearance, distortion and code quality at a representative speed. Then engineer stable handling, triggering, focus, guarding and extraction for the line.

Arrange a PET sample marking trial with Oxford Traceability.

Frequently asked questions

Direct answers for buyers.

Recommendations are confirmed against the real material and production line.

Can CO₂ laser mark clear PET bottles?+

Often yes, producing a light frosted code, but clarity, wall thickness, formulation and speed affect the result. Samples should be tested.

Will laser marking weaken a PET bottle?+

An unsuitable setting could cause excessive thermal effect. Trials are used to obtain the required contrast while checking distortion and container acceptance criteria.

Can a laser mark PET bottles at beverage-line speeds?+

CO₂ laser is used on fast beverage lines, but achievable speed depends on code content, bottle handling, marking window, source, optics and material response.

Reapprove the code when the PET bottle changes

A bottle change should trigger a review of the marking result, even when the pack size and code artwork stay the same. Lightweighting, a revised preform or a different bottle supplier can change the material presented to the laser at the marking position. A previously acceptable sample is evidence for that version of the container, rather than every future bottle with the same nominal capacity.

Keep an approved marked bottle with its supplier reference, revision and agreed marking location. When packaging changes, compare the new bottle at that location and repeat the code assessment with the intended production message. Review visual contrast, readable content, appearance and the container acceptance checks agreed with the bottle and product owners. Thin-wall PET needs particular attention to the relationship between wavelength and material response.

Make the change review part of the purchasing brief so packaging procurement knows which updates need to reach engineering. If a new 2D code is added at the same time, include the revised symbol size and available marking time. Send current and proposed bottles together to support a focused comparison before the new packaging enters routine production.

Does an unchanged bottle capacity mean the laser setup remains suitable?

No. Supplier, wall distribution or material changes can affect the marked area even when the nominal bottle size is unchanged.

What should be retained from an approved PET marking trial?

Keep the marked reference bottle, bottle revision, code artwork, marking location and agreed acceptance evidence for later comparisons.

Arrange a comparative PET marking trial Plan QR and Data Matrix laser codes