Why do handle holes and bottom creases tear in paper bags?

Find where the tear starts

A tear running outward from a cord hole can relate to hole form, remaining board to the edge, cut quality or cord contact. Separation along the top turn-in directs attention towards reinforcement, bond area or folding stress. A cracked gusset and an opening bottom are not the same fault.

Inspect the first whitening or fibre split, not only the final broken edge. Once the bag has come apart, that evidence may be lost. Photographs during filling, lifting and setting down make the revision more specific.

Check the hole with the actual cord and knot

Cord thickness, weave, path through the hole and the internal knot or fixing change how force reaches the board. A hole diameter alone is not enough. Review a sample of the production cord, its pull direction and the finished connection together.

Read corner form, cut cleanliness and remaining board to the top edge as one system. When reinforcement is used, the body and reinforcement holes must share the same centre without allowing the cord to shift the layers. A universal edge distance or kilogram rating cannot replace the project sample.

The top turn-in spreads force into the body

A top turn-in does more than create a neat edge. It changes layer build-up and the way handle force enters the bag wall. If the turn-in does not seat, reinforcement shifts or the bond is interrupted, load can concentrate in a narrow strip. A sound hole beside an opening fold is a useful distinction.

Bonding on laminated or otherwise finished board should not be inferred from plain stock. The converter must verify its adhesive method on the finished surface and actual reinforcement; die manufacture does not imply bag assembly.

Watch grain and folding sequence in the gusset

A side gusset contains inward and outward creases in one panel. If one line resists, material can gather as the bag opens; an over-compressed line may be weakened before use. Watch the assembled gusset move instead of judging it only on the flat dieline.

Grain direction changes that movement. Sheet layout should preserve the direction of principal folds as well as material yield. Increasing crease pressure without diagnosing the cause can move the crack to another line.

Separate a torn bottom crease from an open bond

Fibre separation along a bottom crease is a material or folding failure. A flap releasing along its adhesive line can look similar at first, but it is a bonding fault. Record flap overlap, crease position and bond area separately.

With the intended product inserted, the base should sit evenly rather than loading one corner or a short section of fold. Total weight is not enough information by itself; product size, shape and weight distribution also matter.

Build the trial from production components

Use production board, finish, reinforcement, bonding method and actual cord. Fill the bag with the intended product, then observe likely starting points while lifting, carrying briefly, setting it down and lifting again. This compares one project sample; it does not establish a general load rating for other constructions.

• Does the actual cord and knot seat cleanly in the hole?
• Do body and reinforcement holes share the same centre?
• Do the top turn-in and reinforcement sit continuously?
• Does whitening or cracking begin at one gusset crease?
• Do bottom flaps sit flat and balanced around the product?
• Does damage start at a cut edge, crease or bond line?