The bag is a flow-control device, not a filter
During pressing, the bag is a pressurized porous container. Heat has thinned the resin, the press is driving it out of the puck, and every gram of extract has to pass through the bag wall. How quickly it does that is governed by flow-through-a-porous-medium physics (Darcy's law), and the bag sets three of the variables the press cannot: its permeability (mesh and where the seams interrupt it), its effective flow area (which surfaces stay open as exit paths under load), and the path length resin must travel to an exit (folds, flaps, and bottom seams lengthen it).
Flow rate is more than throughput. Faster, channeled flow means shorter press time, and less time-at-temperature, which is one of the governing variables of the aromatic degradation described in The Closed Collection Path. Slower, choked flow raises pressure inside the bag until the weakest structure, usually a seam, lets go. That's the blowout. Bag design is therefore a yield decision, a quality decision, and a reliability decision at the same time.
Four ways a conventional bag fails
Seam Trapping
Stitching in the flow path is a low-permeability wall. Resin pools at seams and wicks into the thread, and that extract stays in the bag.
Bottom-Seam Obstruction
A stitched bottom seam sits right across the natural exhaust path, the highest-pressure region, where flow demand is greatest and permeability is lowest.
Blowouts
Choked flow is a flow-path problem as much as a pressure problem: internal pressure climbs until a seam gives way and plant material ends up in the extract.
Taper & Flap Trapping
Tapered bases collapse under load and close the channels resin was using; flaps and fold-overs add stagnant pockets where resin collects and cools.
The V3.7 answer, feature by feature
The Access Rosin Improved Rosin Extraction Bag (V3.7) is a fold-over-bottom, side-seam-only, flapless, non-tapered design that forms directional exhaust channels. Each feature is aimed at one of the failure modes above. This is flow engineering applied to a consumable, not a new micron rating.
| V3.7 feature | Failure mode it addresses | What it does to the flow |
|---|---|---|
| Fold-over bottom (no bottom stitching) | Bottom-seam obstruction; seam trapping at the highest-pressure zone | Takes the low-permeability seam out of the primary exhaust path and shortens the path to an exit. |
| Side-only seams | Seam trapping along the flow path | Keeps stitching out of the flow field. Seams run with the flow, not across it. |
| Flapless geometry | Flap and fold resin trapping; snagging while loading | Removes stagnant pockets and dead volume for a smooth interior surface. |
| Non-tapered base, directional channels | Taper collapse; random choked flow; blowouts | Holds defined exit channels open under load and relieves internal pressure through controlled exits. |
| Increased capacity & durability | Overfilled bags; seam stress at high load | Keeps a given charge in a workable pressure window and raises the failure threshold. |
The first stage of the closed path
The bag governs the micro flow path (from the source material to the mesh exit). The press governs the macro flow path (from the plates, off the heat, into the seated collection cylinder). In the Access Rosin architecture the two are continuous: the bag and parchment pouch are positioned so their geometry defines the internal flow channels, which is why the bag and parchment are designed as components of the press, not as isolated articles. A controlled bag makes the press architecture's collection advantages fully effective; an uncontrolled bag would waste them. The V3.7 bag is the first stage of the same functionally closed collection path. Functionally closed, not sealed or airtight.
An honest boundary. The claims here are qualitative and mechanism-based: yield, blowout-rate, and aroma comparisons require controlled testing and are not asserted as numbers. This is engineering design intent, not a medical, therapeutic, or certification claim.
Common questions
No. Micron sets the mesh permeability, but the bag's construction (where the seams sit, whether the base tapers, whether folds or flaps trap resin) sets the flow area and path length just as much. Two bags at the same micron can flow very differently under load. See the V3.7 rosin bags.
A blowout is usually a flow-path problem, not simply too much pressure. When flow is choked by a bottom seam across the exhaust path, or by a tapered base collapsing and closing channels, pressure builds inside the bag until a seam fails. Keeping defined channels open under load is how the V3.7 geometry is designed to relieve that pressure.
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