Material & storage guide
How to Store Filament: Vacuum Packs, Humidity & Shelf Life
Knowing how to store filament matters before the first spool reaches a printer. An OEM shipment may pass through transport, an overseas warehouse, a distributor and an opened sample bench. Each handoff needs a clear storage routine. This guide connects vacuum packaging, inventory records and printing checks, using the published WJ PLA Basic and PETG Basic technical data sheets as grade-specific examples.
Quick answer for buyers
To store filament, keep unopened spools sealed under the exact grade’s stated conditions; after use, reseal opened spools in an airtight bag or container with serviceable desiccant. A drybox helps limit renewed exposure, while absorbed moisture requires grade-specific drying. WJ’s PLA Basic and PETG Basic TDS documents state conditional storage and processing guidance. OEM buyers should confirm bag, seal, desiccant, labels, warehouse conditions and acceptance checks with WJ for the order.
1. Start with the vacuum pack at goods receiving
A vacuum pack is a protective barrier, not proof of the filament’s moisture content. Check the bag and heat seal before putting cartons into saleable stock. Do not open every spool simply to inspect it; agree a receiving sample plan that preserves the remaining packs.
Use a receiving checklist for your own warehouse or overseas fulfillment partner. These are recommended buyer controls, not a claim that every WJ shipment has undergone a measured humidity test.
- Match grade, color, net weight and batch identification to the order.
- Inspect sampled bags for punctures, loose seals or loss of vacuum; photograph any damage.
- Confirm the specified desiccant and label details on sampled packs.
- Separate damaged or questionable stock and contact the supplier with batch and carton references.
2. Give overseas warehouse stock a traceable location
Keep sealed cartons in a clean, stable indoor location away from direct sunlight, water and heat. Protect packs from sharp shelf edges and handling damage. Record temperature and relative humidity near the stock rather than relying on a weather report. A warehouse RH reading is not a moisture-content measurement inside the polymer.
Maintain a batch ledger with receiving date, stated shelf-life basis, location and packaging condition. Use first-in, first-out when equivalent lots have the same expiry basis; use first-expiring, first-out when confirmed expiry dates differ. Keep opened demonstration or inspection spools separate from sealed saleable inventory.
Before a long storage period or another shipment, inspect a planned sample of packs again. If stock moves from a cold location into a warm, humid room, allow the sealed pack to approach room conditions before opening and inspect for condensation. Include the destination climate and expected storage duration in the OEM packaging brief.
3. Open, label and reseal the spool after use
Record the opening date and retain the grade and batch reference. Secure the filament end so it cannot slip under another winding, then put the spool back into an airtight bag or suitable sealed container after printing. Close the full seal and keep the bag away from puncture hazards.
Use serviceable desiccant and follow its supplier’s replacement or regeneration instructions. Indicating desiccant and a container hygrometer can help monitor the enclosure; neither independently certifies the filament is dry. A saturated packet should not be treated as permanent protection.
- Before printing: identify the spool, check storage history and consult its TDS.
- After printing: secure the end, reseal, check desiccant and record the location.
- After an exposure incident: isolate the spool, document the event and evaluate drying before reuse.
4. Read storage and drying numbers by exact grade
The table below uses WJ-TDS-PLABASIC-001 and WJ-TDS-PETGBASIC-001, both V1.0, issued August 1, 2026. These are WJ stated reference instructions, not independent certification of a delivered batch. The 24 months entry applies to the stated sealed storage conditions for these two grades; it is not a universal filament shelf life.
The drying row comes from the “Drying before printing” entries. The storage sections also give separate re-drying windows: PLA Basic 45–55°C for 4–6 hours and PETG Basic 60–65°C for 6–8 hours. These are different contexts, not interchangeable universal recipes. Confirm the applicable routine, current TDS, spool temperature limit and dryer capability before treating a spool.
| Source entry | WJ PLA Basic | WJ PETG Basic |
|---|---|---|
| Storage before use | 15–25°C · below 50% RH · sealed | 15–25°C · below 50% RH · sealed |
| Stated sealed shelf life | 24 months | 24 months |
| Drying before printing | 50°C · 8 h | 65°C · 8 h |
| Protection | Reseal with desiccant; avoid sun and UV | Reseal with desiccant; avoid sun and UV |
5. Distinguish a drybox from active drying
Polymaker’s technical guidance distinguishes airtight storage with desiccant from active drying. Prusa likewise explains that a drybox limits moisture uptake during printing and that already wet filament needs drying first. A bag or passive box does not establish that an absorbed moisture problem has been removed.
Choose a drying profile for the exact material and a dryer that controls temperature suitably. Follow the spool’s limits as well as the polymer instructions. After drying, protect the spool from renewed exposure. For moisture-sensitive grades or long prints, confirm whether feeding from a protected drybox is appropriate; do not reuse PLA settings for PETG, nylon or another grade.
6. Troubleshoot suspected moisture with a controlled comparison
Popping, bubbles, rough extrusion, increased stringing and weak layer bonding can point to moisture exposure. They are clues, not a diagnosis on their own. Temperature, retraction, feed resistance and a partially blocked nozzle can produce overlapping problems.
Record the suspect spool’s storage history and print a small repeatable test. Apply the confirmed grade-specific drying routine, then repeat the same geometry with the same printer and profile. Compare appearance and extrusion with an approved reference spool. If the problem persists, investigate the printer and profile as well as the material; do not keep increasing drying temperature without checking the limits.
- Keep the spool and batch identifier with before-and-after photos.
- Record actual dryer setting, duration, printer, nozzle and profile.
- Return the evaluated spool to sealed storage and document the outcome.
- Ask WJ about the exact grade and order if packaging damage or a batch issue is suspected.
7. Treat shelf life as a conditional inventory rule
A stated sealed shelf life is different from an opened spool’s usable life. The WJ example sheets list 24 months under their specified before-use storage conditions. Confirm the date from which the period is counted and any order-specific shelf-life terms; resealing does not restart that period.
An opened spool has additional exposure history. There is no single number of days that makes every grade safe in every climate. The PLA Basic storage section advises printing within four weeks after opening in humid climates; that advice is specific to the cited grade and conditions, not a promise for every PLA product. Evaluate older or poorly documented stock before distributing it as ready-to-print material.
8. Put storage requirements into the OEM order brief
Send WJ the exact grade, color, spool weight, destination and expected warehouse duration. Add your bag format, desiccant, opening and resealing needs, batch labels and receiving sample plan. If you need a measured packaging or moisture criterion, name the test method and ask whether that documentation can be supplied before ordering.
WJ’s existing vacuum-packaging and warehouse articles provide factory process context. They do not establish the climate control of your overseas warehouse or replace order-specific acceptance records. Use the material library and source TDS documents alongside those articles to prepare a practical sample request.
Procurement notes
| Material & route | Exact grade, color, destination climate and expected transport and warehouse time. |
|---|---|
| Protective packaging | Bag and seal specification, desiccant, spool protection and resealing requirements. |
| Traceability | Batch identification, date basis, carton labels and inventory rotation rules. |
| Acceptance | Receiving sample plan, damaged-pack handling and agreed documentation. |