Ultimate Guide to Curing Cannabis in Mylar Bags

Mylar curing is having a moment. I am still slightly sceptical.

Mylar bags have become the default retail wrap for flower. That shift has crept back into home curing, which is not always a good thing. (custom420.com)

Yes, cannabis can be cured in Mylar. The more honest answer is that it cures well only when your drying is disciplined. (custom420.com)

Glass jars remain the safer choice for flavour development. Mylar can be brilliant for bulk handling, especially once you stop treating it like a sandwich bag. (custom420.com)

Custom 420 framed the debate neatly in October 2024. Their piece is a useful starting point if you want the basics in plain language. Custom 420 Supply. (custom420.com)

Dry first. Don’t try to cure your way out of a bad dry.

The best Mylar cure begins before the bag appears. Drying is where harshness is either avoided or baked in for weeks. (gamutpackaging.com)

For a controlled dry, aim for 15°C to 21°C. Keep relative humidity at 45% to 55% in darkness with gentle ventilation. (gamutpackaging.com)

Commercial guides often quote 7 to 10 days for drying under those conditions. Slower drying tends to protect terpenes, provided you don’t invite mould. (gamutpackaging.com)

Don’t chase a brittle snap on every stem. You want the outside crisp, yet the centre still slightly pliant before you move into curing. (gamutpackaging.com)

Mylar is not one product. Choose it like you would choose packaging for fragrance.

Mylar is a polyester film used to protect contents from light, oxygen exposure, moisture movement. Heat sealing is part of the appeal. (custom420.com)

If you buy the cheapest bags online, expect cheap results. The bag is now your curing chamber, plus your odour barrier, plus your handling system.

As a rule, choose a size that lets the flower sit loose. Overcrowding bruises trichomes, which is the cannabis version of scuffing calf leather.

These are the features I look for:

• Proper zipper plus a heat seal strip
• Opaque film for light control
• Gusseted base for upright storage
• Space for a mini hygrometer

Bag size is a quality decision, not a storage decision

In bag curing, volume matters because moisture equalises across the mass. Too much flower in one bag creates wet pockets, then mould follows.

YLTPACK publishes a simple size guide aimed at pound bags. The dimensions are close to what most packaging suppliers sell. YLTPACK. (yltpacking.com)

If you want a tidy reference, this is a workable cheat sheet. I have added gram weights since nobody in London buys “a pound” with a straight face.

Nominal capacity	Approx weight	Approx bag dimensions	Use case
0.25 lb	About 113 g	6 inch x 9 inch x 3 inch	Small personal batches
0.5 lb	About 227 g	8 inch x 12 inch x 4 inch	Medium batch cure
1 lb	About 454 g	10 inch x 15 inch x 4 inch	Bulk handling with care
2 lb	About 907 g	14 inch x 20 inch x 6 inch	Operations with tight process control

Don’t “make it fit”. A half filled bag cures more evenly than a stuffed one, even if your shelf looks less impressive.

The Mylar cure routine that actually works

Start curing when flower moisture is still present, yet controlled. Commercial references put the start point at roughly 12% to 15% moisture content. (gamutpackaging.com)

Fill the bag to about 75% capacity. Add a small hygrometer or a humidity pack, then store the bag in a cool dark place. (custom420.com)

Marijuana Packaging calls 58% to 62% the ideal relative humidity inside the container. That is the band where aroma tends to open up without the crisping edge. (marijuanapackaging.com)

Burping still matters with Mylar. Gamut’s commercial schedule is a solid framework, even if you shorten the open time for smaller bags. (gamutpackaging.com)

A practical burp schedule for Mylar

Use this as a baseline for the first eight weeks. It is closer to how disciplined operators work, rather than how forums talk. (gamutpackaging.com)

Week	Open frequency	Open time	Target internal RH
Week 1	Twice daily	About 15 minutes	58% to 62%
Week 2	Once daily	About 10 minutes	58% to 62%
Weeks 3 to 4	Every other day	About 5 minutes	58% to 62%
Weeks 5 to 8	Twice weekly	Brief air exchange	58% to 62%

Humidity control. Do it properly, or don’t pretend you’re curing.

Custom 420 gives a wider safe band of 55% to 65% humidity. That is realistic for everyday growers with imperfect rooms. (custom420.com)

Marijuana Packaging is tighter at 58% to 62%. If you can hold that range, flavour tends to stay bright for longer. (marijuanapackaging.com)

Humidity packs are the easy button, though they’re not magic. In the UK, expect a price rise every winter, plus the usual brand premium at specialist shops.

My own view on tools is simple. Spend money where it stops you making a stupid decision at midnight.

• Mini hygrometer, typically £8 to £20
• Impulse heat sealer, often £25 to £80
• Humidity packs, around £6 to £15 per multipack
• Decent Mylar pound bags, commonly £0.30 to £1.20 each in small quantities

Oxygen absorbers, heat seals, plus the point where curing becomes storage

Heat sealing is the clean finish. Custom 420 notes you can seal Mylar with a sealer machine, plus an iron, plus a hair straightener. (custom420.com)

They also mention oxygen absorbers as a further step. I would keep absorbers for storage, not for the active first weeks of curing. (custom420.com)

Once cure is stable, sealing makes sense for travel, retail handover, long term odour control. This is where Mylar beats a cupboard full of jars.

Custom 420 even claims cannabis can stay fresh for months, sometimes years, in Mylar. That assumes stable temperatures plus no repeated opening. (custom420.com)

Where Mylar curing goes wrong, plus how to catch it early

The main failure mode is excess moisture trapped in the bag. The second is overdrying, which leaves you with loud aroma in the bag, flat smoke in the grinder.

Watch for ammonia notes, a sour edge, condensation inside the film. If you see any of that, stop. Take everything out, then re dry at 15°C to 21°C with 45% to 55% RH. (gamutpackaging.com)

Gamut puts the quality target at 8% to 12% moisture content. If you can’t measure it, use feel, then stay conservative. (gamutpackaging.com)

If mould appears, don’t bargain with it. Bin it, then clean your drying space like you’re preparing a Mayfair tasting room for a critic.

Timing, patience, plus what “premium” actually looks like by week eight

Marijuana Packaging suggests curing at least 2 to 4 weeks. They also call 4 to 8 weeks optimal, with connoisseur grade cures stretching far longer. (marijuanapackaging.com)

Custom 420 gives a shorter working range of about two weeks to a month. That is fine for casual use, yet it rarely gives a truly polished aroma. (custom420.com)

I judge week eight flower the way I judge a good Eau de Parfum. It should lift quickly, then settle into layered notes, then keep a clean finish.

If you want a real example, try curing a pungent modern cultivar like Gelato in Mylar. You’ll learn fast if your room is too warm.

A final word from a retail editor who cares too much about packaging

If you cure in Mylar, respect the method. Dry slow, then monitor RH like you mean it, then burp to schedule. (gamutpackaging.com)

Mylar is a smart tool for bulk handling, plus an excellent storage format once the cure is stable. It’s not a shortcut to quality. (custom420.com)

If you want more background reading, I would start with Marijuana Packaging. Then read