You rip open a pack of stinky coffee or add a pungent herb to a bag. Within a few minutes, the entire room is filled with the scent. 

Some enjoy it. Others don't. This is where things get exciting with custom Mylar bags. But the question that counts is this: do they seal in the smell?

Quick Answer

Yes, making smell-proof Mylar bags is possible. If they're sealed and thick enough. It's the heat seal or heavy-duty zipper that really keeps the smell in. Without it, even the best bag will dissipate odors.

The Science Behind the Seal

Mylar is rolled polyethylene terephthalate, sometimes aluminized. Imagine it as a wall so dense with molecules that air molecules, water molecules, and odor molecules can't get through. Tack on a fine heat seal or zipper closure, and voilà, the nose can't pick up what's inside.

That's why coffee roasters, pot dispensaries, candy makers and even snack food producers enjoy having these bags around. They all desire to preserve freshness, yet not cause their products to fill up storage facilities with residual odors.

Mylar-valved coffee keeps the full aroma for 12 months compared to a mere 3 months with paper packaging.

Does Every Mylar Bag Stop Smells? 

Short answer: not all. 

Material thickness is also significant. Thicker bags retain odors more than thinner ones. Seal quality is also important. If a bag is not sealed sufficiently, even the strongest film won't hold scent.

And naturally, custom Mylar bags have varying constructions. Some are reinforced for smell management. Some are designed with visual or branding considerations.

So yes, most custom Mylar bags are smell proof, but only if they're properly barrier layer-built and sealed up tight.

Why Smell Proof Is Important

Consider customers. When someone purchases an eighth of flower and just shoves it in their backpack, they don't want everyone on the entire bus to know what they just purchased. Same with a chocolate bar with herbs infused. Privacy is part of the buy.

For companies, discretion is not the only concern. Smell leakage can actually cause losing flavor. The same molecules that travel through the air are the molecules that need to be captured along with the product.

Odor control is not about covering up a scent, it's about stopping what makes the product its product in the first place from escaping.

The worldwide smell-proof packaging market will reach $1.2 billion by 2027, demonstrating how high the demand is.

Real-Life Uses

Coffee; Degassing valve specialty Mylar bags are used by espresso coffee roasters to vent gas without sacrificing aroma.

Hemp; Dispensaries rely on smell proof bags to keep product discreet and in regulatory packaging.

Food; Snack manufacturers depend on them to keep chips, gummies, and baked goods fresh in flavor and odor-free from the pantry.

Home storage; although some actually do keep their jerky, spices, or emergency food kits stored in them where it is the better to keep scents away. 

92% of cannabis consumers report odor control as one of the most critical packaging attributes they seek.

Testing Smell Proof Claims

Curious folks sometimes run their own experiments. They’ll put in something pungent, like onions or garlic, seal the bag, and set it aside. A few hours later, they sniff around.

With a properly sealed Mylar bag, the smell usually doesn’t escape. Try that with a plain plastic zipper bag, and you’ll notice the difference instantly.

Are Custom Options Just as Strong?

Yes, when done correctly. When businesses buy private label Mylar bags, they're intending on doing graphics, color, finishes, and perhaps window cuts.

None of these products must weaken the barrier as long as the producer is using high-quality films and still retains the structure.

Right, you can still have a foil-stamped logo, flashy color or matte finish without sacrificing smell protection. But it is once sealed that the magic happens.

Heat sealing, child-proof zippers, or thicknwss all contribute to whether and to what extent the bag is "smell proof."

7 out of 10 snack companies experienced a drop in complaints from customers about "stale" food when they upgraded to Mylar packaging.

A Few Things to Remember

1. Seal it tight. Not even the crème de la crème bag will work if it is left open on one side.

2. Thicker = stronger. Use at least 5 mil or bigger if odor protection is needed.

3. Heat seal! Zippers are a blessing, but heat sealing is even better. Having both together is best for ultimate protection.

4. Storage conditions matter. Heat or pressure can degrade barriers over time.

Goods packed in 5 mil Mylar bags are fresh for approximately 40% longer than goods stored in thin plastic bags.

So, Are They Smell Proof?

Yes, most custom Mylar bags close odors in well. But "smell proof" is dependent on quality, thickness, and sealing process. The higher the quality of construction, the better the outcome.

To any odorous product manufacturers or seller, smell proof customized packaging is an unwanted add-on. It's a promise to your client/customer and protection of your product's flavor, long term jevity, freshness and secrecy.