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What Does Sift Proofing, or Sift-Resistant Sewing, Mean?


You may have heard the terms “sift proofing” or “sift-resistant sewing” in bulk bags discussions. What is sift proofing in bulk bags and what does it mean for your company? Read on to learn more.

What Is Sift Proofing?

Sift proofing refers to the steps a bulk bag manufacturer takes to prevent leakage of product from the bag through the seams. Leakage can mean lost product, which can cost your company money. It can also mean excess product ends up on your factory floor, which can present both health and safety hazards for your employees. The established method of sift proofing is sift-resistant sewing, also called anti-sift sewing.

What Is Sift-Resistant Sewing?

Sift-resistant sewing, or anti-sift sewing, is the most common method manufacturers currently use for sift proofing a bulk bag. The procedure involves sewing a soft yarn or a special felt into the seams of the bag. While sewing, the operator keeps the sift cord along the bag’s seam so it fills the spaces by the needle hole.

What Is a Sift-Proof Seam?

A sift-proof seam is a felt or downy material attached to the seam as part of the sift proofing process. Leaks can happen because the sewing needle can make minuscule holes in the fabric. That will not be a problem for most dry goods, but with fine powder goods like milk or cocoa powder, the sifting, or displacement caused by the air in the bag could lead some of the material to escape through these holes in the seam.

By attaching the sift-proofing material, you prevent any goods from escaping through sifting and leaking. The sewing operator can sew the felt next to the threaded sift cord or in between fabric panels.

What Is a Double Chain Stitch?

Sewing operators can use a number of different stitching methods to construct bulk bags. Double chain stitching is a branded stitch method utilized by Midwestern Bag. This type of stitch reduces loose threads and fibers to ensure a cleanly and professional product is produced. Not only will double chain look cleaner, it also helps reduce leakage due to the thickness of the thread covering the needle holes made during the sewing process.

What Are Other Ways to Prevent Sifting?

When constructing sift-proof bulk bags, the yarn or felt must be thick enough to cover the needle holes. Using too thin of material can cause product to escape during or after filler. Additionally, the use of polyethylene liners can act as a sift-proof method to ensure no leakage occurs.

For high-quality, sift-proof, woven polypropylene bags that are reliable, durable and can meet all your bulk dry goods storage and transportation needs, contact Midwestern Bag & Supply today.


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