Custom reclosable polybags : Common pitfalls to avoid

6-22-16

We make millions of custom reclosable polybags every year.  While anything is possible, we have experienced some things that lead us to suggesting alternatives to help avoid some potential pitfalls when ordering custom reclosable bags.  We hope they help you.  We can send FREE hand made samples of most any size desired if needed.

1. Must account for spot-welds: The spot-welds reduce the bags at the opening by up to 3/8”.  Spot welds (also referred to as “crimps” or smashes”) are the flattened areas at the side of the bag where the reclosable zipper meets the side weld seal.   Spot-welds exist on each bag on both sides of the zipper.   The area where the zipper meets the side seal is flattened to provide for the strongest side seal.  Without flattening the area, the zipper profile would be too thick a material to seal consistently.    The end use may force a wider width to account for the existence of the spot welds.  For example, if a 4×4 card needs to slide into a custom reclosable bag, ordering a 4.5×4.5 would be a more likely size to order.   We can provide hand-made samples at no charge for most sizes to ensure the proper size for the end use.
2. Avoid printing in the zipper channel: Custom reclosable polybags are made by first printing rolls of material on a print press and then converting the printed rolls into custom bags on a bag machine.   Applying a reclosable zipper to a printed area of the material can pose sealing issues.  While we can apply a zipper through ink under certain conditions, we generally recommend avoiding ink in the “zipper channel”.  The zipper channel is defined as the area in which the zipper will lay down on the bag.  Allowing for a 3/4” wide or more area of no print for the zipper to lie down will provide for the strongest seals and best reclosable feature.  If you have an application where the zippers needs to be placed on ink, let us know as we can accommodate some requests depending on ink colors, bag size and overall quantity.
3. 1” area above the zipper :   Our standard is to make custom reclosable polybags with 1” area above the zipper.   At times we get request for 1/2” above the zipper.  While we can accommodate ½” request, we do not recommend it.  Opening and closing custom reclosables is easier with 1” above the ziplok when compared to a lesser amount.  The zipper profile location can also vary slightly (up to ¼”) depending on the specifics of the item due to inherent needed tolerances .  The 1” above the zipper helps seamlessly absorb the potential variation without loss of functionality.
4. LDPE reclosable side weld polybags are not leak-proof:   Leak-proof ziplok bags need the ¼” wide side seams often found on a laminated bag.   Leak-proof ziplok bags generally carry high minimums.  We do not make leak-proof custom reclosable polybags.
5. LDPE reclosable side weld bags are not barrier bags:  Air, moisture and light move through the walls of a side weld reclosable polybag.   If the end use for the bags needs protection of any type (air, water vapor, light etc), a laminated bag is needed.  Laminations are a combination of material “glued” together to provide the package the needed properties to elongate the contents shelf life.   End uses such as raisins, beef jerky, cheese, snack foods and fertilizer all need barrier protection to protect the contents from outside elements.   End uses such as bread, ice, apples, paint brushes and top soil do not need barrier protection.  Laminated barrier reclosable bags generally carry a high minimum and high cost.    LDPE reclosable bags are generally available in lower volumes at a lower cost.  We do not make laminated bags. We do make the LDPE reclosable bags.

The picture shows a few custom reclosables we have recently made:  the purple print shows where the zipper channel has been left open for the zipper lay-down and the green Spax print has drawn-in arrows pointing to the spot welds.

Thanks for reading!!