Common Open Mouth Bag Terms


Open mouth bags are bags used in the packaging industry that are factory closed on one side of the tube, and closed by sewing or sealing on the other side. The materials, construction, and characteristics of open mouth bags vary widely, making them suitable for diverse applications ranging from bulk solids and fertilizer, to seed and pet food. Let's review some common terms that are associated with Open Mouth Bagging:


The state of sticking together two or more materials

Adhesive – Hot Melt

An adhesive that is solid at room temperature, liquefied by heat, applied in molten state and forms a bond by cooling and solidifying (Hot Melt Adhesive Bag Sealer)

Aluminum Foil Laminations

A combination of aluminum foil with a paper backing used as a barrier and often combined by means of an adhesive or extruded polyethylene

Back Seam Woven Bag

A woven bag that contains a seam on its backside

Basis Weight

The weight in pounds or grams of a given area of paper

Biaxially Oriented Polypropylene (BOPP)

A polypropylene film that has been stretched in both the machine and cross directions


The ability to break down through the action of naturally occurring microorganism over a period of time

Bursting Strength

The point at which a bag will rip due to high pressure, expressed in pounds per square inch

Cap Sac

A pinch bottom bag with a detachable inner liner – a bag within a bag (Cap Sac Sealer)

Cap Sac - Bag within a Bag


Simultaneous extrusion of two or more plastic layers together to form a single multi-layered film

Cold Seal

Sealing a packaging product by the use of pressure as compared to heat

Cure Time

The time required for a material to set at a given temperature and humidity


The separation of the components of a laminated material


The weight per unit of volume

Drop Test

Determining bag strength by dropping filled bags from predetermined heights and positions until failure occurs


The process of melting resin to apply to paper or to bond film or foil to woven material

Face Width

The width of the front side of an open mouth bag

Fill End

The portion of an open mouth bag that is left open so the contents can be added into the bag before closing/sealing

Flexible Packaging

Packaging that utilizes materials such as paper, foil, film, etc.

Flush Cut Top

Open mouth bag walls that are cut off evenly across the top; not stepped-end cut


Caliper or thickness expressed as 100 time millage, e.g. 1 mil = 100ga


The side (or bottom) portion of an open mouth bag which allows for volume (Hot Air Sealer for Side Gussets)

Heat Seal

Bond together with heat and pressure

Heat Reactivation Closure

A closure constructed of thermoplastic resin allowing it to be sealed with the application of heat. Primarily used with pinch bottom sacks.

Heat Sealable Bag

A term applied widely to a variety of open mouth bags composed of surface-coated papers that can be sealed by the application of heat

Heat Sealable Paper Bag

Hot Melt Adhesive

A thermoplastic adhesive composed of polymers, resins, and/or waxes (Hot Melt Adhesive Bag Sealer)


Having the property of readily absorbing atmospheric moisture

Impact Strength

The amount of impact an open mouth bag can withstand before it tears

Laminated Paper

A combination of two or more sheets of paper, film or foil bonded together in order to make a sheet stronger or more resistant to moisture, grease or odor


Combining multipole layers of material into a single structure


A very thin coating of metal deposited on film or foil


The caliper of thickness expressed in mils. 1 mil = One thousandth (1/1000) of an inch or 0.001 inch

Moisture Barrier

Prevents the movement of moisture from one area to another

Moisture Vapor Transmission Rate

The rate of grams of moisture that will pass through an area of 100 square inches of barrier material in a 24 hour period – expressed as gm/100 sq in/24 hr

Open Mouth Bag

A sewn or sealed bag, factory closed at one end

Oxygen Transmission Rate

The rate of cubic centimeters that pure oxygen will pass through an area of 100 sq inches of barrier material in 24 hours – expressed as cc/110sq in/24 hr

PE Coated Paper

A paper coated with polyethylene

Pillow Style Bag

A versatile, economical, bag style with a bottom, top, and back seal, applicable to almost every industry and application

Pinch Bottom Open Mouth Bag (PBOM)

An open mouth bag formed with adhesive applied to an extended lip (stepped end cut top) on the bag opening along with part of the bag face. After filling the bag, the extended lip of the bag can be heated to re-activate the adhesive – the adhesive coated lip is then folded over the bag opening and pinched to close the bag (Pinch Bottom Bag Closer)


A generic term for polyolefins, including polyethylene and polypropylene (Poly Bag Sealer)


A thermoplastic material composed solely of polymers of ethylene (PE)


Any of various thermoplastic resins that are polymers of propylene – hard and tough and used to make molded articles and packaging materials

Post Gusseting

The operation of forming a longitudinal tuck or gusset into each side of a continuous tube of material – typically done in a secondary operation after the material has been formed into a tube. These gussets typically form the sides of a back which is closed on one end prior to filling.

Roll Fold Glue (DRC)

An operation done to the top or bottom of a side gusseted bag in which the bag is folded over twice in the same direction and glued in position to close off the bag.

Seal Strength

The force a seal can withstand before it breaks apart

Sewn Closure

A method for closing bags – plain or tape closure – with special bag sewing machines

Sewn Open Mouth Bag (SOM)

Open mouth bag that is closed using sewing thread

Sewn Over Tape

The tape sewn into the closure of a multiwall sack – also known as Fold Over Tape

Sewn Over Tape Bag

Shear Strength

The strength of a material or component against the type of yield or structural failure where the material or component fails along plane as a result of forces acting parallel to the plane

Stepped End Cut Top

A flat or gusseted open mouth bag with the face, gussets and back stepped at different lengths so that a flap or extension of the front, on one end of the bag tube and a flap on the back surface of the opposite end is produced


Any material such as paper, film, and foil to which adhesives, inks, or coating are applied


The inclusion of an information tag in the closure when the filled bag is closed – typically done with sewn closures (Bag Tag Placer)

Tape Closure

The sewn closure of filled bags incorporating sewn over tape

Tearing Strength

The force required to tear a bag

Tensile Strength

The maximum load a material can support without fracture when being stretched

Tubular Woven Bag

A woven bag that contains no seams

Water Vapor Transmission Rate

The grams of moisture that will pass through an area of 100 sq. inches of material in a 24-hour period, expressed as gm/100sq in/24 hr

Tubular Woven Bag

A woven bag that contains no seams

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