Burnt Residue on the Seal Jaw: How It Ruins Your Bags (Wire-Brush Tips)

Burnt Residue on the Seal Jaw

How It Quietly Ruins Your Bags

Vertical Packaging Machine Encyclopedia · Article 19

Cover: scorched residue on a hot jaw, wire brush cleaning

Bags won't seal and leak when you squeeze — your first move is to turn the thermostat. But veterans check the jaw first. That black, hard crust is the real culprit.

01 How the “Crust” Forms

“The end-seal jaw halves run hot, so the film easily adheres to them.”
— VFFS manual §4.6

Fig. 1: How the crust forms and ruins seals (from manual §4.6)

The principle is simple: the jaw is hot, the film sticks on pressure; tear, re-stick, tear again — the scraps scorch and carbonize into a dark hard crust.

02 Why It Ruins Bags

“If not cleaned in time, it leads to weak bag seals, so clean the jaws frequently.”
— VFFS manual §4.6

•  Uneven crust makes heat transfer hit-or-miss; the seal pattern turns black and patchy;

•  Result: weak or torn horizontal seals, and side-seal bursts.

⚠  In the fault table, both “weak horizontal seal” and “side-seal burst” list the same cause — dirty jaw. Clean before touching temperature.

03 The Right Way: Wire Brush with Silicone Oil

“If film scraps stick to the side/end seal surfaces, brush them off with a wire brush dipped in silicone oil.”
— VFFS manual §6.1

Fig. 2: Before/after + 3 wire-brush tips (from manual §6.1, fault table)

✔  Silicone oil is not optional — it leaves an anti-stick film on the jaw so the film stops welding on.

04 Quick Reference

Table 1. Jaw-related faults (from manual fault table)

Final Thoughts

Remember the order: check the jaw first, then adjust temperature. Many “temperature problems” are solved with a brush.

Jaw still won't stay clean?  Reply with keyword "jaw" for the cleaning diagram; send a photo of your jaw and our engineers will tell you if it needs replacing.