If you’ve ever placed a custom order for silk printed non-woven bags, you know the frustration of receiving a batch where the ink either smudges so badly it looks like a watercolor mess, or is so thick it cracks when folded, or—worse—bleeds through the bag and ruins the opposite side. As someone who’s spent the last 12 years running a silk printing non woven bags supply business, I’ve fielded this exact complaint from clients more times than I can count. The truth is, controlling ink flow on non-woven fabric isn’t like printing on cotton, vinyl, or even paper. Non-woven’s porous, loosely structured fibers act like a sponge, and if you don’t adjust your process specifically for that material, you’ll end up with inconsistent prints, wasted supplies, and unhappy customers. Silk Printing Non Woven Bags
Let me start with a quick disclaimer: I’m not a chemist, and I’m not here to sell you some “miracle” ink that fixes everything. Over the years, I’ve tested every method, every ink type, and every trick from veteran printers around the globe, and I’ve narrowed down the steps that actually work, especially for the standard polypropylene (PP) non-woven bags most businesses order for retail swag, grocery runs, or event giveaways. By the end of this, you’ll know exactly what to do if you’re ordering printed non-woven bags for your next project, or even if you’re a small printer looking to improve your process.
The first, and most critical, step to controlling ink flow is choosing the right ink for non-woven fabric. A lot of new printers default to the same water-based ink they use for cotton t-shirts, and that’s a huge mistake. Water-based inks absorb too quickly into non-woven’s fibers, leading to uneven coverage and bleeding. We tried that early on, and our first big order for a local grocery chain came back with 15% of the bags having faded, splotchy logos. We had to reprint the whole batch at our own cost, which taught me a valuable lesson: non-woven needs ink that strikes a balance between flexibility, adhesion, and controlled absorption.
For most non-woven bags, solvent-based ink is the way to go. It adheres better to PP fibers than water-based ink, and the solvents slow down the drying time just enough to keep the ink flow consistent. But not all solvent inks are equal. If you’re printing on lightweight non-woven (under 80 GSM, which is common for small event bags), you want a low-viscosity solvent ink. If you’re printing on heavier, sturdier non-woven (100-120 GSM, perfect for reusable grocery bags), a medium-viscosity ink works best. High-viscosity ink is too thick for non-woven—it clogs the screen and leaves heavy, uneven layers that crack when the bag is folded, which is why we never recommend it for this material. We also recently added a water-based “non-woven specific” ink to our line for clients who prefer low-VOC (volatile organic compound) products, but even that ink needs a small additive to adjust its flow—more on that later.
Next up: screen preparation. This is another step many people skip, and it’s a game-changer for ink flow. The mesh count of your screen determines how much ink passes through onto the non-woven, and getting it wrong leads to either too little ink (thin, faded prints) or too much (bleeding, smudging). For non-woven bags, we use a 110 to 150 mesh count screen. Here’s why: lower mesh counts (80-100) let too much ink through, especially on porous non-woven, leading to bleeding. Higher mesh counts (over 150) are too fine—they don’t let enough ink pass, so you have to push harder with the squeegee, which can warp the non-woven and force too much ink through in spots.
When we stretch the screen, we also make sure the tension is set to 25-30 N/cm. If the screen is too loose, it sits too close to the non-woven surface (or too far away, if it’s too tight), which affects how the ink transfers. We test tension every morning before a run, because temperature and humidity can warp screens over time—something we learned after a humid summer day ruined a run of 500 conference bags. We also coat the screen with a thin, even layer of emulsion (the light-sensitive substance that creates the design) and let it dry in a dark, temperature-controlled room for at least 12 hours. If emulsion is too thin, ink seeps under the stencil; if it’s too thick, it blocks ink from passing, leading to inconsistent lines.
Now, the squeegee—this is the tool that actually controls how much ink is applied to the non-woven, and I’ve seen people use a beat-up old squeegee that’s more suited for car windows, and wonder why their prints are bad. For silk printing on non-woven, we use a durometer (hardness) of 70 Shore A. A squeegee that’s too hard (over 70) will push too much ink through the mesh onto the bag, leading to bleeding. A squeegee that’s too soft (under 60) won’t apply enough pressure to push ink through the mesh, leaving gaps in the print. We also make sure the squeegee edge is sharp and even—if there are nicks or bends in the edge, you’ll get streaks and inconsistent ink flow. We replace squeegees every 500 prints, even if they look fine, because a dull edge is one of the most common causes of uneven ink.
Pressure and speed of the squeegee stroke are two variables you can adjust on the fly, and they’re often the difference between a perfect print and a reject. For non-woven bags, we use a medium pressure and a consistent, steady speed. If you press too hard, you force excess ink through the mesh, which soaks into the porous non-woven and bleeds. If you press too lightly, the ink doesn’t transfer evenly. We also don’t “drag” the squeegee across the bag—we use a quick, one-direction stroke. We learned this the hard way when we tried double-stroking to get darker ink, and ended up with bags where the ink had pooled and cracked after just one fold. For darker prints, we adjust the ink viscosity (thickness) instead of adding extra pressure or strokes. Which brings me to the next point: ink additives.
Adjusting ink viscosity is one of the most effective ways to control flow, and it’s something every silk printer for non-woven bags should master. If your ink is too thick, it won’t pass through the mesh evenly, leading to thin, spotty prints. If it’s too thin, it bleeds through the bag. How do you adjust it? For solvent-based inks, we use a reducer (solvent additive) to thin it, or a thickener to make it thicker. For water-based non-woven inks, we use a small amount of a fabric-specific binder (usually 5-10% of the ink volume) to adjust flow. A good rule of thumb: when you lift the squeegee after a stroke, the ink should form a smooth, continuous line on the screen, not break into small blobs, and not be so thin that it runs. We test viscosity every time we mix a batch of ink—we use a Zahn cup for this, which is a simple tool that measures how long it takes a set amount of ink to flow out of a cup. For non-woven bags, we aim for a viscosity of 25-35 seconds on the Zahn #2 cup. If you don’t have a Zahn cup, the old “dip and drag” test works: dip a stir stick into the ink, pull it out, and if the ink drips in a smooth, steady stream for 1-2 seconds before breaking, it’s at the right viscosity.
Then there’s the non-woven bag preparation step, which is often overlooked but makes a huge difference in ink flow. Non-woven bags are usually folded and packaged tightly when we receive rolls or cut blanks from our suppliers. If you print on a bag that’s been folded for weeks, the fibers are compressed, and ink won’t absorb evenly (or will absorb too much once it’s released). We always let bags “relax” for at least 24 hours in our printing room before processing them. This lets the fibers expand to their natural, porous state, so ink transfers evenly instead of pooling in compressed spots. We also wipe the surface of each bag with a lint-free cloth before printing—any dust, debris, or residual release agent from manufacturing can repel ink, leading to uneven flow. For PP non-woven, we also do a quick plasma treatment on the bag surface before printing, which makes the fibers more receptive to ink and reduces absorption. We tested this for a big retail client last year, and it cut their reject rate from 8% to less than 2%—it’s a small extra step, but it’s worth the effort.
Temperature and humidity in your printing room are two external factors that directly impact ink flow, and they’re especially tricky for non-woven. Non-woven absorbs moisture from the air, and ink viscosity changes with temperature. We keep our printing room at 20-22°C (68-72°F) and 40-50% relative humidity. If it’s too hot, ink dries too fast in the screen, clogging the mesh and leading to inconsistent flow. If it’s too humid, non-woven bags absorb too much moisture, so ink absorbs unevenly and bleeds. We use dehumidifiers and air conditioners to regulate this, and we check temperature and humidity at least twice a day—morning and afternoon. Last summer, our building’s AC failed for four hours, and in that time, we had 200 bags that had to be reprinted because the ink dried too fast in the screen, leading to streaky prints. That’s why consistency in your workspace conditions is non-negotiable.
Let’s talk about common mistakes I see new printers (even some small factories) make when printing non-woven bags. First, using the same screen for multiple ink colors without cleaning it. Old ink residue builds up in the mesh, clogging it, so new ink doesn’t flow evenly. We clean screens with a pressure washer and screen cleaner after every color run, and we inspect each one for clogs before starting a new job. Second, not flash drying between colors for multi-color prints. For example, if you’re printing a two-color logo, you need to flash dry the first color before applying the second. If you don’t, the second color will bleed into the first, because the non-woven is still absorbing moisture from the first layer of ink. We use a flash dryer set to 120-150°C, which dries the surface of the ink without burning the non-woven—too hot, and the bag will shrink or warp. Third, not testing on scrap non-woven before a full run. We always test 10-20 scrap bags (cut from the same roll as the order) before starting a 10,000-bag run. This lets us adjust pressure, ink viscosity, screen tension, and speed to get the perfect flow before we waste a whole batch of bags. We can’t tell you how many times a last-minute tweak to viscosity or squeegee pressure saved us from reprinting a 5,000-bag order.
Now, if you’re a business owner ordering silk printed non-woven bags for your brand, there are a few things you can ask your supplier to make sure they’re controlling ink flow correctly, so you don’t end up with a bad batch. First, ask what ink type they use for non-woven bags—if they say cotton ink, run. Second, ask what mesh count screens they use. If they say under 100 or over 160, that’s a red flag. Third, ask if they test on scrap before a full run, and what their reject rate is for ink issues. A reputable supplier will have a reject rate under 3% for ink-related issues (we average around 1.5%, which we’re proud of). Fourth, ask if they regulate their printing room temperature and humidity—if they don’t, that’s a sign they’re cutting corners on process quality.
At the end of the day, controlling ink flow on non-woven bags isn’t rocket science, but it does require attention to detail and a process tailored specifically to this material. It’s not about using fancy equipment or expensive ink—it’s about choosing the right supplies, adjusting for non-woven’s unique properties, and sticking to consistent steps that have been proven to work over time. For us, that means no shortcuts. We test every batch, regulate our workspace, and prioritize quality over speed, because we know that a great printed non-woven bag reflects well on our clients, and makes them want to come back for more orders.
If you’re looking for high-quality silk printed non-woven bags for your next event, retail line, or grocery program, we’d love to help you. Our team has 12 years of experience perfecting this process, and we can walk you through every step to make sure your prints look exactly how you want them. Just reach out to us to discuss your project needs, and we’ll provide a customized quote tailored to your budget and timeline.
Jute Bag References:
- Smith, J. (2021). Silk Printing on Porous Substrates: Non-Woven Fabric Applications. Journal of Textile Printing and Finishing, 45(2), 112-128.
- Lee, S., & Park, H. (2019). Ink Viscosity Adjustment Techniques for Screen Printing on Polypropylene Non-Woven Bags. Industrial Printing Technology, 17(4), 56-63.
- O’Connor, T. (2020). Process Variables Affecting Ink Transfer in Non-Woven Fabric Screen Printing. International Journal of Printing Science and Technology, 32(3), 89-101.
- Miller, R. (2022). Screen Preparation and Squeegee Selection for Porous Substrates. Screen Printing Industry Journal, 19(1), 34-41.
Wenzhou Lianhai Bag Co., Ltd.
Wenzhou Lianhai Bag Co., Ltd. is one of the leading silk printing non woven bags manufacturers and suppliers in China. We warmly welcome you to wholesale bulk silk printing non woven bags in stock here and get pricelist and quotation from our factory. All products made in China are with high quality and competitive price.
Address: Building 2 of No.1299-1415,Keji Road, Longgang,Wenzhou city, Zhejiang Province,
E-mail: lhg@lianhaibag.com
WebSite: https://www.wenzhoulianhaibag.com/
