Heating defect
Blisters & bubbles in thermoforming
Also called: Moisture blisters
Blisters are raised bubbles that appear as the sheet heats, most often when moisture absorbed by a hygroscopic material flashes to vapour — or when the sheet is over-heated.
Why it happens
- Hygroscopic material (PET, PETG, PC, ABS) not pre-dried
- Sheet over-heated past its window
- Trapped volatiles or contamination in the sheet
- Storage in humid conditions before forming
How to fix & prevent it
- Pre-dry hygroscopic grades to spec before forming
- Reduce oven temperature/time to the material window
- Store sheet dry and sealed
- Use fresh, contamination-free material
How Indu prevents it: We pre-dry hygroscopic grades to specification and store sheet controlled — and forming sheet we extruded ourselves means moisture and cleanliness are managed end to end.
Troubleshooting help
Fighting blisters & bubbles on a part?
Send your drawing, sample or a photo of the issue — our engineers will diagnose the cause and reply with the tooling, material and process fix, usually within 24 hours.
ISO 9001:2015 certified · Most quotes back within 24 hours