Coated vs Uncoated Bulk Bags: What the Spec Sheet Doesn’t Explain

Most bulk bag spec sheets list “coated” or “uncoated” as a single line item. No explanation of what the coating does, what it doesn’t do, or why it matters for your specific product. Buyers either ask for coated by default, assuming it means better, or skip it without thinking because the price is lower.

Both decisions can be wrong. A coated FIBC bag used for a product that needs to breathe traps moisture inside and accelerates spoilage. An uncoated jumbo bag used for a moisture-sensitive product lets humidity in and ruins what’s inside. Neither failure is dramatic. Both are preventable, once you understand what the coating is actually doing.

At Mewar Polytex, we’ve been manufacturing PP woven bulk bags for buyers across 25+ countries for 45+ years. Coating specification is one of the most common points of confusion we see, and one of the easiest to get right once it’s explained clearly.

What Coating Actually Is

First, a quick clarification, because the word “coating” gets used loosely and it confuses buyers.

The coating on a bulk bag is not a chemical spray or a surface treatment. It’s a thin layer of polypropylene film that gets laminated onto the woven fabric during manufacturing. The woven fabric is fed through a machine that bonds a thin plastic film to one or both sides of the weave.

That film fills in the small gaps between the woven threads. Those gaps are what make uncoated woven fabric slightly porous, air and fine particles can pass through them slowly. The coating closes those gaps, making the fabric much more resistant to moisture and dust passing through the bag wall.

That’s it. Coated means the gaps are filled. Uncoated means they’re open. Everything else follows from that one difference.

Coated vs Uncoated Bulk Bags: What Each One Actually Does

Coated FIBC Bags

A coated FIBC bag has that polypropylene film bonded to the fabric, typically on the inside, the outside, or both sides depending on the application.

What this gives you:

• Moisture resistance: humidity and light water exposure don’t penetrate the bag wall easily. Moisture resistant bulk bags keep product inside dry even in humid storage or transit conditions.
• Dust containment: fine particles can’t work their way through the fabric wall during handling and vibration.
• Better print surface: the smooth film surface holds ink cleanly and produces sharper, more vibrant print quality than uncoated fabric.
• Reduced breathability: this is a feature for most products, but a problem for products that need airflow. More on that below.

Coated bags are the right choice when your product is sensitive to moisture, needs to stay dry, or when presentation and print quality matter, especially in industrial bulk packaging applications.

Uncoated FIBC Bags

An uncoated FIBC bag has no film layer. The woven fabric remains slightly porous, air and moisture vapour can pass slowly through the bag wall in both directions.

What this gives you:

• Breathability: breathable FIBC bags let air circulate through the bag wall, preventing heat and moisture from building up inside.
• Lower cost: no lamination step in manufacturing means a lower unit price.
• Lighter weight: marginally lighter per bag, which adds up across large shipments.
• Less print clarity: the textured woven surface doesn’t hold ink as cleanly as a coated surface.

Uncoated jumbo bags are the right choice when your product generates heat or moisture from within, or when breathability is more important than moisture exclusion.

Problems Caused by Choosing the Wrong Bulk Bag Coating

This is what the spec sheet doesn’t tell you, and where the real cost of getting it wrong shows up.

Coated bag used for a product that needs to breathe. 

Fresh produce, firewood, and some seeds release heat and moisture continuously. In a coated bag, that moisture has nowhere to go. It builds up inside, condenses on the bag wall, and creates exactly the humid conditions that cause spoilage, mould, and quality loss. The bag isn’t faulty. It’s doing its job, keeping moisture out. The problem is that the moisture is coming from inside.

Uncoated bag used for a moisture-sensitive product. 

Cement, fertiliser, food ingredients, and chemical powders absorb moisture from the air. In a humid warehouse or transit container, an uncoated bag lets that ambient humidity slowly pass through the fabric wall and into the product. Cement clumps. Fertiliser cakes. Food ingredients lose shelf life. It’s a gradual process that often isn’t noticed until the product reaches the end user.

For export shipments moving through humid port environments and long container transit cycles, coating selection becomes especially important. A specification that performs well on a 200 km domestic route can fail on a 30 day sea journey to West Africa or Southeast Asia.

Our common problems in bulk packaging guide covers this and other specification mismatches that show up as product quality issues downstream.

Which Products Need Coated vs Uncoated FIBC Bags?

If your product sits in the middle, seeds for example or certain agri-inputs, it’s worth discussing the specific moisture sensitivity with your supplier before defaulting to either option.

Coating vs Lamination: A Quick Clarification

Buyers sometimes use “coated” and “laminated” interchangeably. They’re related but not identical, and the distinction matters when you’re specifying bags.

• Coating on a bulk bag refers to the polypropylene film bonded to the woven fabric, what we’ve been discussing throughout this blog. It’s a functional layer that affects moisture resistance and breathability.
• Lamination, as in BOPP lamination on woven bags, refers to a higher-quality, print-grade film applied to smaller woven bags, primarily for retail and branding purposes. BOPP laminated bags are a different product category from bulk FIBCs, they’re used for consumer-facing packaging like flour bags, seed bags, and food-grade retail packs.

For bulk bags carrying 500 kg to 2,000 kg, the relevant term is coating, not lamination. If a supplier quotes you a “laminated FIBC,” ask them to clarify what they mean.

For more on BOPP lamination and where it applies, our BOPP laminated bags for industrial packaging blog covers that product category separately.

Bulk Bag Specifications Buyers Should Confirm Before Ordering

Once you’ve decided on coated or uncoated, confirm these details before production:

• Coating side: inside only, outside only, or both. Inside protects the product, outside improves print quality, both sides gives maximum protection at higher cost.
• Coating weight (GSM): heavier coating gives better moisture resistance but slightly reduces flexibility. Match the weight to your product’s sensitivity.
• Safe working load: confirm the weight requirement so the fabric GSM is specified correctly. Coating doesn’t affect load capacity.
• Print requirement: coated bags produce sharper print. If branding or compliance text matters, coated is almost always the right choice.
• Liner requirement: for highly moisture-sensitive products, a PP or aluminium liner adds a second barrier inside the bag.
• UV stabilisation: essential for bags stored outdoors, significantly extends usable life.
• MOQ: coated FIBC bags involve an additional manufacturing step. Confirm minimum order quantities upfront.

For a broader look at what goes into specifying the right bulk bag, our how to choose the right FIBC bag guide walks through the full set of variables, and FIBC bags – types and applications gives context on where different formats are used.

Why Customers Trust Mewar Polytex

Coating specification depends on your product’s moisture behaviour, your storage and transit conditions, and what you’re protecting against. The right answer is rarely the same across two different product lines.

We manufacture both coated and uncoated FIBC bags across 14+ facilities, with weaving, coating, stitching, and finishing all handled under one roof. With in-house weaving, coating, stitching, and finishing across 14+ facilities, Mewar Polytex maintains tighter consistency across production batches, critical for buyers who depend on predictable moisture protection and bag performance.

For procurement teams buying in volume, that batch-to-batch consistency is what separates a reliable supplier from a problem one. A coating spec that varies between runs affects your product protection in ways that only show up after the bags are filled and in transit.

Final Word

Coated and uncoated bulk bags aren’t better or worse than each other. They solve different problems.

Coated bags keep moisture out, right for cement, fertilisers, food ingredients, and chemical powders. Uncoated bags let air move through, right for fresh produce, firewood, and materials that don’t need moisture protection.

Getting it wrong doesn’t usually cause a dramatic failure. It causes quiet, gradual product quality issues that are easy to miss until a buyer complains. Specifying the right coating from the start is a small decision that prevents a much larger problem later.

Tell us your product type, storage conditions, filling weight, and export requirements. Our team will recommend the right coated or uncoated FIBC specification for your application.

Share the details through our inquiry form and we’ll come back within 24 working hours with a recommended coating spec, sample plan, and a clear quote.