Six constructions, six different jobs. A short decision guide covering how you fill, what you are protecting against and how the bag has to sit on a pallet — and the questions worth answering before you ask anyone for a price.
Most packaging enquiries begin with a price question. It is almost always the wrong place to start, because the constructions in a paper-laminated range are not competing versions of the same bag — they solve different problems. Pick the construction first and the price conversation becomes straightforward.
Here is how the range differs in practice, and which build tends to win for a given product.
Start with how you fill
Three things decide almost everything: how the bag is filled, what it has to keep out, and how it has to sit once it is full.
Filling comes first because it is the least negotiable. An automatic line needs dimensional consistency and will not tolerate a bag that varies in width; a hand-filled operation will happily take a bag cut to any size. Get this wrong and no amount of barrier engineering rescues the specification.
Central sealed (C.S.) — the automatic-line default
A centre-sealed bag is formed as a tube and closed with one seam down the back, so the sides are folds rather than stitching. Every bag in the run comes off the same width, which is exactly what an automatic filler needs.
It also gives you the largest uninterrupted print area in the range, because nothing crosses the front panel.
Typical fits: cement, skimmed milk powder, PVC resin, dyes and intermediates, guar gum.
L-type stitched — the flexible workhorse
An L-type bag is cut flat and closed with one continuous stitch down a side and along the base. Because it is cut rather than tubed, any width can be made without retooling — which makes short runs, odd sizes and trial quantities straightforward.
It suits hand and semi-automatic filling, and it is usually the right answer when you are moving several products in several pack sizes.
Typical fits: sesame seed, isabgol, spices, cattle and poultry feed, bentonite powder.
Box-type / block bottom — when the filled bag has to stand
Gusseted sides and a pasted flat base mean the filled bag holds a brick shape instead of slumping into a pillow. Pallets cube out properly, containers load square, and the bag stands unaided on a shop floor.
The flat face is also the best print surface we make, because the panel does not curve away as the bag fills.
Typical fits: cement, wall putty, tile adhesive, pet food, rice and flour.
Metalized — when light is the problem, not just water
Kraft and film handle moisture. They do nothing about light, and light is what oxidises fats and fades pigments. A metallised film ply laminated onto the face adds a light, aroma and vapour barrier, and gives you a mirror-bright ground to print on.
Specify it where shelf life is long and where the pack is doing sales work as well as protection.
Typical fits: premium feed, fish feed, seeds, spices, pigments, pet food.
Multiwall paper — the all-paper alternative
A multiwall sack carries its strength in the number of kraft walls rather than in a woven ply. Three plies is the common build; four is specified for heavier fills and longer supply chains. Where moisture matters, a poly ply goes in between the papers.
Choose it where you want a fully recyclable paper construction, or where your filling line is already set up for valve bags.
Typical fits: food grains, flour, sugar, potato flakes, carbon black, starch, fertilizers.
Liners and rolls — components, not categories
HM, LD and HDPE liners add a moisture or contamination barrier inside any of the bags above. Most buyers arrive at a liner as the answer to a problem they discovered elsewhere in the specification, rather than as a starting point — but if your product is hygroscopic or food-grade, raise it early, because it changes the outer bag too.
Laminated fabric on the roll is for a different buyer entirely: converters, corrugated-box makers and companies forming and filling on their own plant.
Still not sure?
Tell us the product, the fill weight, how the bag is filled and whether it faces a customer. That is usually enough to narrow six options down to one, and we will say so plainly if a simpler construction would do the job.
