PETG is an amorphous copolyester and normally remains clear through thermoforming when processed within the grade’s window. Excessive heat exposure can produce haze, bubbles, surface texture, sticking, or loss of optical quality.
PETG should not be diagnosed as though it crystallizes in the same way as standard PET. Haze in PETG is more likely to involve overheating, degradation, moisture where applicable to the product, surface damage, or incomplete contact.
Correction
The cycle should minimize unnecessary dwell after the sheet becomes formable. Heater uniformity is critical because a local hot zone may haze while the rest of the part remains clear. Storage, masking, and supplier recommendations should be checked for the actual sheet grade.
If haze follows the tool rather than the heater or sheet, trapped air and surface finish should be investigated. Increasing pressure cannot restore clarity once the sheet has been thermally damaged.