A gusseted bag is a bag with an inward-folded allowance, the gusset, along its sides or at its base. The gusset lets the bag lie flat when empty and expand to gain volume when filled. It is common in shops, boutiques and wherever boxed products are carried.
A reinforced bag is one whose handle area is strengthened with an extra layer of film or a separate handle piece. The two features can also be combined: the gusset provides volume, the reinforcement provides confidence in carrying. On this page we cover the two together.
Types of gusset
The gusset determines where the bag will expand. Which gusset is chosen depends on the shape of the product to be carried. A bottom gusset is generally preferred for boxed or folded products, and a side gusset for bulky but light products.
- Side gusset: Inward-folded allowances on both sides of the bag. It can be formed on the film line while the bubble is being flattened.
- Bottom gusset: An inward-folded allowance at the base of the bag; the full bag can stand upright.
- Block bottom: The base is turned into a rectangular surface by sealing; suitable for box-shaped products.
Handle and reinforcement options
In gusseted bags, the handle is solved in several different ways. A grip hole punched in the body is the simplest method; if an extra piece of film is sealed around the hole, a reinforced patch handle is obtained. This reinforcement lets the load be carried over a wider surface rather than a thin edge.
For heavier products, separately produced loop or strip handles can be sealed onto the body. This solution adds an extra sealing step to the bag’s production process and makes the soundness of the seal seam even more important.
The gusset gives the bag volume; the reinforcement keeps that volume carryable.
What raw material is it made from?
Gusseted and reinforced shop bags are mostly made from LDPE and LLDPE blends. LDPE gives the film a soft feel, a glossy surface and easy sealing. LLDPE adds puncture and tear resistance along with high elongation.
Unlike the stiff, rustling feel of a t-shirt bag, this blend produces a bag that feels softer and of higher quality in the hand. In printed shop bags, the gloss and evenness of the surface are also part of the appearance, so the choice of raw material affects the print result as well.
Production steps
The process starts on the blown film line. In side-gusseted bags, the gusset can be formed by pushing the film inwards from both sides while the bubble is being flattened. A bottom gusset, on the other hand, is created at the converting stage by folding the film.
A large share of gusseted shop bags are printed. Before printing, the film surface is prepared with corona treatment; otherwise the low surface energy of polyethylene makes it hard for the ink to adhere. Printing is mostly done by flexographic or rotogravure printing.
At the cutting and sealing stage, the bag length is cut, the edge and bottom seams are made, the reinforcement piece or handle is added and the grip hole is punched. Because the number of layers increases in places at this stage, the sealing settings must be made carefully. Quality control checks whether the print is in position, the consistency of the colours, the seal seams and the handle strength.
How it differs from a t-shirt bag
At first glance, a gusseted shop bag and a t-shirt bag do the same job: both carry the product. But the expectations of use differ. A t-shirt bag is usually given out for a single shopping trip, and being light and economical comes first. A gusseted shop bag acts like the brand’s shop window; it is visible while carried and can be used several times.
This difference is also reflected in the choice of material and thickness. In shop bags, the film is generally thicker, the surface glossier and the print more carefully done. The handle is solved either as a reinforced patch handle or as a separate piece. Instead of cutting the handle from the film as in a t-shirt bag, the aim is to spread the carrying load over a wider area.
If a shop bag is expected to be used several times, this expectation should also be taken into account at the production stage. The seal seams of the reinforcement piece, the points where the handle joins the body and the edges of the gusset folds are the places that wear most under repeated use. Filling and emptying the bag several times during sample testing makes it easier to see how these points behave.
Questions to ask when choosing
When ordering gusseted bags, the dimensions should be thought of in three dimensions: width, length and gusset depth. Starting by measuring the box or folded form of the product to be carried reduces surprises later on.
- Will the product stand upright in the bag or lie flat?
- Will the handle be carried in the hand or hung on the shoulder?
- Will the print be on one side or both, and in how many colours?
- Is the bag expected to be used once or several times?
The answers to these questions together determine the film thickness, the need for reinforcement and the handle shape. Before a large order, testing a sample with the real product is the safest way to see both appearance and strength at the same time.