A Song-dynasty porcelain dish often breaks at unpacking not because the crate was too weak, but because one material decision went wrong: the foam was plasticised PVC, the plasticiser migrated onto the glaze over several months, the foam hardened and shrank, restraint disappeared, and the object travelled inside its own box until it struck a wall. Failures in art transport rarely come from a single violent impact. They come from an overlooked microclimate, an outgassing liner, an unsecured object, and a monitoring record that cannot be reproduced.
JUNZHIJIA's protection principle is that an artifact case is a controlled microclimate first and a container second. The crate must hold temperature, relative humidity, vibration, pollutants and biological agents inside acceptable bands simultaneously, and it must make every journey traceable, checkable and repeatable. The sections below break the problem into inert materials, humidity conditioning, shock isolation, sealing strategy and courier documentation.
Table of Contents
- Failure Modes and Protection Targets for Artifact Cases
- Inert Materials: From the Oddy Test to ISO 16245
- Acid-Free Liners and Barrier Films: Building the Layers
- Silica Gel Conditioning and Target RH Bands
- Humidity Buffer Design and Data Logger Monitoring
- Shock and Vibration Isolation for Ceramics, Glass and Ivory
- Internal Restraint: Custom Cradles and Padded Cavities
- Preventing Pests, Mould and Biological Deterioration
- Sealed Versus Vented Microclimates
- Relative Humidity Setpoints by Material Class
- Crate Structure, Stacking Loads and Pressure Equalisation
- Courier Documentation and Handover Checks for Loans
- Frequently Asked Questions FAQ
- Conclusion and Related Reading
Failure Modes and Protection Targets for Artifact Cases
Failure in artifact transport falls into three clear grades. Grade one is permanent physical damage: fractured ceramics, shattered glass, split ivory, lifting paint layers. Grade two is progressive chemical deterioration: accelerated metal corrosion, embrittled and yellowed paper, hydrolysis of organic material. Grade three is information failure: without monitoring records nobody can tell whether the environment ever left its band, so later assessment is guesswork. Grade three is the easiest to overlook and the one that makes the other two impossible to attribute or prevent.
A workable artifact case has to satisfy four target groups at the same time. The environmental group means relative humidity held within plus or minus three percent of the target band, a daily temperature swing under five degrees Celsius, and no acidic gases or plasticiser vapour inside the cavity. The mechanical group means the peak acceleration experienced by the object stays below its brittle threshold under the expected transport profile, and long-term vibration does not cause relative movement or abrasion. The biological group means the cavity offers no conditions for insect eggs or spores to develop and imports no external infestation. The management group means there are quantified records before and after unpacking that satisfy the lender's handover requirements.
The quantitative basis for these targets comes from two families of standards. Transport environment and test methods follow the ISTA series, ASTM D4169 and GB/T 4857, with structural strength referenced to MIL-STD-810H Method 514 for vibration and Method 516 for shock. Conservation material and microclimate criteria come from museum practice: the Oddy test, ISO 16245 for cellulosic and polypropylene archive boxes, ISO 9706 for permanent paper and ISO 18916 for photographic activity. Aligning both families at the drawing stage is what separates a conservation-grade case from an ordinary industrial container.
Inert Materials: From the Oddy Test to ISO 16245
The primary criterion for material selection in an artifact case is not strength but whether the material releases anything into the object's atmosphere. Any material sharing a sealed cavity with an artifact for days or weeks is exchanging molecules: plasticiser migration, residual monomer release, acidic gas evolution, hydrogen sulphide and carbonyl compounds. Museums call this risk outgassing and have formalised the assessment as the Oddy test.
The Oddy test logic is direct: seal the candidate material with copper, silver and lead coupons in a closed vessel at 60 degrees Celsius and near-saturated relative humidity for 28 days, then inspect the coupons for corrosion, discolouration or filming. Results classify materials as suitable for permanent contact, suitable for temporary use only, or unsuitable. Lead responds to acetic acid and sulphides, copper to chlorides and organic acids, silver to sulphides, and the three together cover most pollutants. For case design, treat an Oddy result as an entry threshold for liner materials rather than an optional extra.
The second criterion is the chemistry of the material itself. PVC is excluded from permanent-contact lists because of plasticisers; polyurethane foams carry residual isocyanates and amine catalysts; nitrile rubber contains sulphur and acrylonitrile; ordinary urea-formaldehyde plywood releases formaldehyde continuously. The safe side concentrates on polyethylene, polypropylene, polyester film, acid-free board, cotton webbing and silicone, with crosslinked polyethylene foam offering a good balance between cushioning and inertness.
The third criterion is the standardised archival material system. ISO 16245 specifies performance requirements for archive boxes made from cellulosic material and from polypropylene sheet, covering material purity, alkaline reserve and mechanical strength. ISO 9706 governs paper permanence, while ISO 18902 and ISO 18916 cover storage enclosures for imaging materials. Their value is that they convert the subjective claim that a material is safe into metrics that can be sent to a laboratory and re-verified.
There is also a practical purchasing rule. Any liner material should stay in its original packaging after delivery and be stored away from chemicals, and the cutting area must never use chlorinated cleaners or oil-based lubricants. Secondary contamination between delivery and packing is more common than contamination from the material itself.
Acid-Free Liners and Barrier Films: Building the Layers
The interior protection of an artifact case is not a layer of foam. It is a layered structure. Working outward from the object, the sequence is normally contact layer, cushion layer, barrier layer and structural layer, each with a distinct function, and the materials must not interfere with one another.
The contact layer sits against the artifact and must be soft, inert and non-shedding. Typical choices include crosslinked polyethylene sheet, which is closed-cell, plasticiser-free and thermoformable, polyethylene foam board, cotton cloth and polyester fabric. Contact layer hardness should be chosen with restraint. Too hard a contact layer transmits crate vibration straight to the object surface; too soft a contact layer lets the object migrate under acceleration.
The cushion layer absorbs energy. Designers often assume softer is better, but the correct approach matches the cushion curve to the object's fragility class and the expected drop height. Soft foam performs well in small drops but compacts solid in a larger one, after which transmissibility rises sharply. Medium-density foam is more dependable in large drops. The deciding metric is peak acceleration, not how the foam feels by hand.
The barrier layer separates moisture and pollutants. Common options are polyester film, polyethylene film, aluminium-laminate film and microporous materials such as Tyvek. One distinction is frequently confused. A fully moisture-impermeable film cuts the object off from external moisture exchange, so cavity humidity is determined only by the internal conditioning agent, which gives the greatest stability but also means a mistake is harder to correct for a moisture-sensitive object. A microporous film permits extremely slow exchange, which buffers extreme situations but makes performance dependent on how firmly the lid seals.
The structural layer is the crate itself. Wooden crates should use low-formaldehyde plywood with sealed edges, and the interior face can be isolated with aluminium foil or polyester film. Rotomoulded or injection-moulded polymer crates are superior for inertness and cleanability and avoid the egg and mould risks of timber. For a comparison of density, compression strength and resilience across foam families, see Foam Material Comparison.
Silica Gel Conditioning and Target RH Bands
Relative humidity is the single most influential variable in the deterioration rate of collection material. Hydrolysis in most organic artifacts accelerates as relative humidity rises, metal corrosion starts abruptly above a critical humidity, and excessively dry air makes wood, ivory and bone shrink and split. The control strategy is therefore not to be as dry as possible but to hold a narrow band determined by material class.
Silica gel is the most mature humidity control method for artifact cases. The critical step is pre-conditioning before use: select gel already equilibrated to the target humidity point, and place it in the crate once it has stabilised. Using dry gel directly pulls cavity humidity very low, which is actively harmful to wood and organic material. Conditioned gel typically holds 20 to 30 percent of its own weight in moisture, and its equilibrium point shifts with temperature, so the quantity must be sized with margin.
Quantity and buffer capacity can be estimated from free cavity volume and leakage rate, then calibrated by measurement. A practical sequence is to run the empty crate through one complete thermal cycle with a data logger, measure the humidity decay curve, and size the gel mass and replacement interval from that curve. A well-sealed crate with limited free volume needs only enough gel to cover the transport period plus a safety margin, while a deliberately vented crate needs more gel and clearly defined replacement points.
Two engineering details are easily missed. First, the conditioning agent must be separated from the object by a breathable but non-perforated divider to prevent dust contamination and direct contact. Second, it must not sit directly beneath or immediately above the object, because that creates a local humidity gradient and a condensation risk on the surface. The sound arrangement places gel in the corners of the cavity or in a suspended upper layer so moisture circulates naturally.
Temperature is the companion variable. A temperature drop raises relative humidity and a rise lowers it. If the diurnal swing en route reaches 15 degrees Celsius, cavity humidity can shift by more than ten percent, so insulation, thermal lining and gel quantity have to be designed together rather than independently.
Humidity Buffer Design and Data Logger Monitoring
Conditioning agent plus logger is the minimum viable arrangement, but conservation-grade transport usually needs a third element, the humidity buffer. A buffer is a low-density layer with some moisture sorption capacity, such as acid-free card, cotton felt, kapok or a dedicated buffer board. It does not replace the conditioning agent. Its job is to flatten short-period excursions, absorbing or releasing moisture so the response at the object surface is smoothed when outside temperature changes suddenly.
Buffer performance depends on thickness, porosity and exposed area. There is a counter-intuitive design conclusion here: effectiveness is governed mainly by surface area rather than volume. Spreading the same buffer material across the interior walls outperforms stacking it in a corner.
Monitoring is the only way to verify the whole design. The usual instrument is a temperature and humidity data logger, typically set to a sampling interval of five to fifteen minutes, with accuracy of plus or minus two to three percent RH and plus or minus half a degree Celsius. The logger should sit where it best represents the object environment, normally adjacent to the object rather than against the crate wall. For light-sensitive material a light logger can be added.
Three operating rules apply. First, the logger must be calibrated before packing and the certificate retained. Second, data must be downloaded and archived immediately after each unpacking, with filenames matching the transport number and the object number. Third, the data must be aligned with transport milestones such as loading, transhipment, customs clearance and arrival, because only then can a fluctuation be attributed to crate design rather than to one long stationary period.
The data should also be read for trends, not only for limit breaches. A slow rise over several days indicates the conditioning agent is approaching saturation. A periodic sawtooth indicates a breathing material inside the crate or a poor seal. A sudden step usually points to unpacking, resealing or a sharp temperature change. Preserving these curves is the most direct input for improving the next crate design.
Shock and Vibration Isolation for Ceramics, Glass and Ivory
Ceramics, glass, ivory and shell are classic brittle materials: a low elastic limit, essentially no yield plateau, and cracking or fracture once the strain threshold is passed, with no reversibility. The protection priority is to reduce the acceleration the crate experiences down to a level the object can survive.
Shock has three sources: drops during handling, impacts between transport vehicles, and repeated excitation from road or rail surfaces. Drops are counted by height and frequency, vehicle impacts by occurrence, and road excitation as continuous energy input. All three must be treated separately at the design stage. Drops are handled by cushion thickness, impacts by external bumpers on the crate, and road excitation by the fatigue stability of the cushion.
Glass and ceramic differ widely in impact tolerance. Thin-walled glassware is extremely sensitive to local point loading, where a single local impact can initiate a through-crack, while thick-bodied ceramics tolerate whole-body impact better but remain vulnerable at joins, handles and spouts. Restraint design should support projecting features independently rather than relying on the general foam around them.
Ivory, bone and wood suffer from anisotropy. Ivory differs markedly in strength and moisture expansion along and across the grain, and splits readily along the grain when it gains or loses moisture. For these materials the restraint must not be a rigid clamp but a compliant fit: a shape-matching, low-resilience pad that encloses the object, limiting displacement without restricting small dimensional change.
Vibration isolation and shock isolation do not have identical goals. Shock isolation aims to reduce peak acceleration and needs a sufficiently thick compressible layer. Vibration isolation aims to keep the system's natural frequency away from the dominant transport band, which for road and rail typically concentrates between a few hertz and a few tens of hertz. Crate and cradle design should avoid placing a resonance point in that range. Quantitative methods and test conditions are covered in Transport Vibration Testing.
A common error is to wedge the object solid with rigid foam. A wedged object feels secure but converts every crate vibration into direct load on the object, producing micro-cracks and surface abrasion at contact points after long transport. The correct approach combines a definite displacement limit with recoverable compliance, plus an acid-free, low-friction interface material at every contact point.
Internal Restraint: Custom Cradles and Padded Cavities
Internal restraint solves a specific problem: the object must not move freely under acceleration, deceleration and jolting, yet must not be damaged by the restraint itself. These two requirements pull in opposite directions, and the engineering answer is to distribute restraint across many low-pressure contact points instead of concentrating it at one high-pressure point.
A custom cradle is the most dependable solution. It is machined to the object's three-dimensional form so the contact surface follows the curvature and pressure is distributed evenly. Cradle material is usually crosslinked polyethylene board or polypropylene sheet, cut by CNC or formed into a matched cavity. For thin-walled objects the cavity should cover at least the lower third of the height, with independent travel-limiting restraint above to prevent vertical bouncing.
A padded cavity is the lower-cost alternative. A cavity slightly larger than the object is cut into the cushion layer, then compliant soft material fills the gap so the object is enclosed. The critical variable is the gap size. Too large a gap lets the object accelerate and strike the cavity wall; too small a gap applies pressure at insertion. The correct gap is established by test and relates to the object's fragility class and the transport intensity.
Contact surface details determine long-term outcome. All contact surfaces should be acid-free to avoid migration of acidic species during prolonged contact. Abrasive textiles should be avoided because loose cotton fibres embed in glazes and lacquer. Painted, gilded or lifting areas should be completely avoided by the contact surface, with load carried by surrounding sound areas instead.
An acceptance criterion for the restraint system should be measurable. After packing, run a short low-frequency vibration verification and observe whether relative displacement occurs, while logging internal and external acceleration to confirm the restraint is not transmitting crate vibration directly to the object. When the verification passes, archive the cradle number, object number and packing photographs so the same restraint state can be reproduced at the next packing.
Preventing Pests, Mould and Biological Deterioration
Pests and mould are underestimated failure modes because their onset is delayed. Insects may hatch weeks after storage, and mould may only bloom once the object meets a humid environment after arrival. Both share the same root cause: the crate provided suitable conditions, meaning organic material, elevated relative humidity, and imported eggs or spores.
The first principle of pest control is to break the pathway at source. Timber crates, untreated board and natural fibre textiles can all be infestation sources. When specifying crates, avoid untreated solid wood and boards containing bark, and verify the supply chain for board and textiles with freezing or low-oxygen treatment. A safer approach uses polymer crates and acid-free synthetic materials, structurally eliminating the crevices where eggs lodge.
Mould control focuses on humidity rather than biocides. Most moulds need relative humidity above 65 percent to become active, so holding cavity humidity below 55 percent essentially removes the risk while remaining safe for most organic artifacts. The most dangerous moment is the transfer of a crate from a cold or humid environment into a warm room, when condensation can form on the object surface. Slow, staged warming and moisture-absorbing buffers prevent this.
Where the destination carries a known infestation risk, the empty crate can be frozen before packing, holding it at minus 20 degrees Celsius long enough for the core temperature at every point to reach target, then allowing slow return to ambient to avoid condensation. This procedure requires a temperature record as evidence of effectiveness. Chemical fumigants demand great caution because most persist in porous materials and cause secondary damage to metals and organics, and they are rarely the first choice for artifact cases.
Cleanability matters as much. Rotomoulded and injection-moulded crates have dense, seamless, wipeable surfaces that can be fully cleaned between uses, whereas timber and assembled structures retain debris and spores in joints. For crates in long-term circulation, establish a cleaning and inspection procedure and check liners for staining, discolouration or odour after every return.
Sealed Versus Vented Microclimates
There are two fundamental sealing strategies, and the choice depends on how sensitive the object is to humidity fluctuation and how long the journey lasts.
A sealed design uses a continuous gasket, normally silicone or EPDM, compressed by latches to make the cavity a closed boundary for energy and moisture. Cavity humidity is then determined entirely by pre-conditioned silica gel and the buffer, giving the smallest fluctuation, typically within plus or minus three percent of target. This suits humidity-sensitive objects, long-distance transport and international loans crossing several climate zones. The drawback is that the cavity is a black box: a design error leaves the object in the wrong environment for the entire journey with no chance of correction en route. Gasket material selection is discussed in Case Seal Materials.
A vented design retains a small controlled exchange path so the cavity and outside atmosphere exchange moisture very slowly. The advantage is resilience in extremes: moisture migrates out slowly when outside humidity is lower and in slowly when it is higher, avoiding the abrupt change that follows a seal failure in a sealed crate. This suits short journeys, inter-museum transfers in stable climates and robust materials.
Three criteria guide the decision. First, sensitivity: does the object show visible change when relative humidity deviates ten percent from target. Second, duration: does the interval between packing and unpacking exceed 72 hours. Third, external environment: will the route cross a seasonal transition, a climate zone boundary or humid warehousing. Two or more yes answers favour the sealed design.
The two routes are not mutually exclusive. A practical compromise is primary sealing plus buffer: keep the crate sealed but add enough sorption material inside so the cavity responds slowly to outside temperature shocks. This is especially effective in air freight where outside temperature can change abruptly. Where the crate must cross a significant pressure differential, a pressure equalisation valve is also required so the gasket is not forced open or the crate distorted, as explained in Pressure Equalization Valve.
Relative Humidity Setpoints by Material Class
Setpoints cannot be standardised across collections. They must be assigned by material class. The values below are common museum ranges; live projects should adjust them for the individual condition of the object, including previous restoration, salt efflorescence and corrosion products, and for the lender's requirements.
| Material class | Target RH | Tolerance | Primary risk |
|---|---|---|---|
| --- | --- | --- | --- |
| Bronze and iron (chloride-bearing) | 30%-35% | +/-3% | Corrosion above critical humidity, spreading bronze disease |
| Stable inorganic (ceramic, stone, glass) | 35%-45% | +/-5% | Soluble salt crystallisation, glass weeping |
| Ivory, bone, shell | 45%-55% | +/-3% | Grain-direction splitting on drying, swelling distortion |
| Wood and lacquered wood | 50%-60% | +/-5% | Shrinkage cracking, lacquer lifting |
| Silk, cotton and wool textiles | 45%-55% | +/-3% | Fibre hydrolysis, dye migration |
| Paper, paintings and archives | 45%-55% | +/-3% | Acidification, mould, ink bleeding |
| Leather and parchment | 45%-55% | +/-3% | Collagen hydrolysis, alum salt efflorescence |
| Photographic film and gelatin | 30%-40% | +/-3% | Gelatin moisture uptake, emulsion blocking |
| Waterlogged excavated material | 80%-95% (or fully immersed) | +/-5% | Irreversible shrinkage and salt efflorescence on drying |
| Painted plaster and wall painting fragments | 50%-55% | +/-3% | Separation of ground layer from pigment layer |
Mixed packing is another common problem. When a single crate holds both metal and organic material the humidity targets can conflict, and the answer is not to split the difference at some middle value. Separate crates, or physical partitioning inside the crate with independent conditioned chambers, is the correct solution. Partitioning also means that if one chamber loses control the other objects are unaffected.
Once a setpoint is fixed it should be written into the packing list and courier documentation, and re-measured with a portable instrument at unpacking. If the measured value deviates beyond tolerance, record the deviation magnitude, its duration and photographs of object condition as inputs to the subsequent condition assessment.
Crate Structure, Stacking Loads and Pressure Equalisation
An artifact crate carries both mechanical load and environmental protection duties, and the two use different design languages that must be reconciled from the outset.
On the mechanical side, stiffness comes from wall thickness, reinforcement ribs and the geometry of the crate mouth. The lid-to-body interface should be a stepped rebate of some depth so the gasket is evenly compressed and shear loads are resisted. Latch quantity and position should be distributed along the crate length to avoid an under-compressed middle section. Large crates need a pallet base with fork pockets and internal load-bearing beams positioned so stacking loads pass directly into the walls rather than through the cushion above the object.
Stacking loads must be calculated from the actual stacking height. The calculation should include dynamic amplification in transit: multiply the static stack load by a dynamic factor to obtain the load the crate really sees while jolting. Where a crate may sit at the bottom of a container or share a hold with heavy equipment, raise the dynamic factor and locally reinforce the lid. Loading methods follow established stacking load test practice.
Pressure equalisation is specific to air freight. As hold pressure falls, a sealed crate develops a differential that lifts the lid or bulges the body. If the differential forces the gasket open, the crate draws air back in on landing and carries external moisture into the cavity. The solution is a pressure equalisation valve or hydrophobic breather membrane that lets air pass slowly while blocking liquid water and particulates. The valve should be mounted high on the body to avoid being blocked by condensate.
Handles, castors and lifting points also belong in the design. The combined weight of crate and contents frequently exceeds what two people can carry, so four-person lift points or sling attachment points should be provided with a clearly marked maximum sling angle. Lifting points anchored to the lid will distort the sealing face under load and must be anchored to the body instead.
Courier Documentation and Handover Checks for Loans
In loan transport, documentation matters as much as the crate. Without records, even successful environmental control cannot be demonstrated, and incomplete records turn any claim into a dispute.
Courier documentation normally has six components. The first is the packing list, giving object name, number, material, dimensions, weight and condition description. The second is the environmental record: raw data logger files, sampling interval, calibration certificate and pre- and post-packing readings. The third records the specification and quantity of conditioning agent and buffer material. The fourth is the packing process record, including liner material batch, cradle number and packing photographs. The fifth is the transport plan with route, expected duration, transhipment points and emergency contacts. The sixth is the condition report with six-view and detail photographs taken before packing.
Handover checks should be performed at every node: departure, loading, transhipment, customs clearance and arrival. Checks cover crate exterior for dents, scratches and gasket deformation, latch condition, valve condition, tamper seal integrity, and any odour or dampness. Any anomaly should be photographed with a time record and countersigned by both parties.
Unpacking needs a controlled pace. When a crate arrives from a cold or humid environment into a warm room, it should first stand closed until the crate temperature equalises with the room, then be opened. After opening, do not remove the object immediately; let it continue to equilibrate in the partially open state while reading the data logger to confirm the environment stayed within band. Only when readings are stable and object condition is normal should removal and condition review proceed.
Archiving should close the loop. Store the transport record alongside the object file and consult it before the next loan to improve crate design. For objects that travel frequently, build a crate-to-object pairing file recording peak acceleration and humidity excursion for each journey, producing an iterative basis for improvement.
Frequently Asked Questions FAQ
Q: Why can ordinary shock-absorbing foam not be used in an artifact case?
A: Ordinary packaging foam frequently contains plasticisers, residual blowing agents or flame retardants, and inside a sealed cavity over days or weeks it releases organic acids, sulphides and volatile organic compounds that corrode metals, film glazes and yellow paper. The damage is slow and largely irreversible, so it is usually discovered long after the shipment has ended. Material selection should therefore pass an Oddy test or use known inert materials such as crosslinked polyethylene, polypropylene, polyester film and acid-free board. Ordinary foam also has high compression set, so after repeated transport it collapses and loses restraint, allowing the object to migrate inside its own cavity. Contact and cushion layers require separate selection: the contact layer must be inert and non-shedding, while the cushion layer must absorb energy consistently across repeated cycles, and one cannot substitute for the other. Hand feel is not a valid acceptance criterion for either layer. Ask the supplier for the base polymer, the additive list, the compression set figure and an Oddy report before specifying the material.
Q: How should the quantity of silica gel conditioning agent be determined?
A: The quantity depends on four variables: free cavity volume, seal leakage rate, transport duration and the extremes of outside temperature and humidity. No published table covers all four combinations, so sizing must combine calculation with measurement. A workable method is to pack an initial quantity by rule of thumb, run one complete simulated journey with a temperature and humidity logger, then read the decay curve and fluctuation amplitude inside the cavity and adjust the quantity accordingly. Longer journeys or violent external swings call for more gel and clearly defined replacement points along the route. The gel must also be pre-conditioned so that its own equilibrium humidity equals the target value, because using dry gel directly pulls cavity humidity far too low for wood and organic material. Place the gel inside a breathable but non-perforated divider, and distribute it around the cavity rather than stacking it against or above the object, which would create a local humidity gradient and a condensation risk on the object surface.
Q: Should ceramic objects be wedged tight inside the case or left with clearance?
A: Both extremes cause damage, so the answer is neither. The sound approach distributes restraint across many low-pressure contact points. Support the lower third or more of the object in a shape-matched crosslinked polyethylene cradle so the contact surface follows the curvature and pressure stays even, then add independent travel-limiting restraint above to stop vertical bouncing. A completely unrestrained object moves freely under acceleration and strikes the cavity wall, while a rigidly wedged object transmits every jolt straight into projecting features, producing micro-cracks and glaze abrasion at contact points over long journeys. The restraint should be verified after packing by low-frequency vibration while observing whether relative displacement occurs, and internal and external acceleration should be logged to confirm the cradle is not transmitting crate vibration directly to the object. Record the cradle number, object number and packing photographs so the same restraint state can be reproduced at the next packing. Before specifying a gap, confirm the intended gap dimension with a trial pack rather than inheriting it from a previous object.
Q: How should the choice between a sealed case and a vented case be made?
A: Three criteria apply. First, does the object show visible change when relative humidity departs ten percent from its target. Second, does the interval between packing and unpacking exceed 72 hours. Third, does the route cross a seasonal transition, a climate zone boundary or humid warehousing. Two or more yes answers favour a sealed design with a compressed continuous gasket, holding cavity humidity within plus or minus three percent of target. Short journeys in stable climates carrying robust materials can use a vented design, where slow moisture exchange buffers extreme conditions and avoids the abrupt change that follows a seal failure. A practical engineering compromise is primary sealing combined with a buffer layer: keep the crate sealed while adding enough moisture-absorbing material inside so the cavity reacts slowly to outside temperature shocks. Air freight legs benefit most from this arrangement. Whichever route is chosen, the decision and its justification belong in the transport plan so the receiving institution can audit it.
Q: Why can ivory and wood not share the same humidity setpoint?
A: Although ivory, bone and wood are all organic, their response to moisture and their safe bands differ. Ivory expands anisotropically, with a marked difference between expansion along and across the grain, so a rapid humidity change readily starts a split that follows the grain. Wood is governed mainly by moisture content change around the fibre saturation point, and its shrink-swell amplitude is larger and develops more slowly, so it tolerates brief excursions slightly better but moves further over days. Standard museum practice holds ivory, bone and shell at 45 to 55 percent relative humidity and wood and lacquered wood at 50 to 60 percent, with excursion limits of plus or minus five percent in both cases. If the two must travel in one crate, partition them physically with independent conditioned chambers rather than choosing a single compromise humidity value between the two bands, because a compromise satisfies neither material and hides which one is actually at risk. Record both setpoints on the packing list even when the objects share a crate.
Q: What should be done with the data logger records?
A: The value of a logger is not the single verdict of whether a limit was breached but the trend analysis it supports. A slow rise over several days shows the conditioning agent approaching saturation. A periodic sawtooth shows a breathing material inside the crate or a poor seal. A sudden step usually indicates unpacking, resealing or a sharp temperature change. Three practices matter. Calibrate before packing and retain the certificate together with the logger serial number. Download and archive immediately after every unpacking, with the filename matching the transport number and object number so records can still be retrieved years later. Align the data with transport milestones such as loading, transhipment and arrival, so a fluctuation can be attributed to crate design rather than to one long stationary period. Keep these curves in the object file as direct evidence for improving the next crate and for resolving any later condition dispute. A logger that is never read is no better than no logger at all.
Q: Which transport tests should an artifact case undergo?
A: At minimum, vibration, drop, stacking and thermal cycling. Vibration testing verifies the cushion system does not amplify at resonance and checks for relative displacement and abrasion after prolonged excitation. Drop testing uses a height set by crate mass and handling method, checking cushion margin on corners, edges and faces. Stacking testing applies the actual stacking height plus a dynamic factor to verify the load path through lid and walls rather than through the object. Thermal cycling verifies gasket and conditioning system behaviour at extremes, including condensation risk when a crate transfers from cold to warm conditions. Methods follow the ISTA series, ASTM D4169 and GB/T 4857, with structural criteria referenced to MIL-STD-810H. The essential point is that results are only valid for the specific crate configuration and transport route tested, so any change to foam density, liner geometry or route requires re-evaluation rather than an assumption of equivalence. Retain the test report with the crate record for future loan negotiations.
Q: What services can a manufacturer provide for artifact transport?
A: A manufacturer with moulding and liner machining capability can deliver an integrated package from structural design through custom liners to courier documentation. That includes cavity design for cradles from three-dimensional object data, conditioned chambers configured by material class, cushion thickness calculated against the transport route, environmental record templates prepared for loan requirements, and batch consistency certification for liner materials. A capable supplier will also provide the base polymer documentation, compression set figures and Oddy test reports that a lender's conservator is likely to request, and will retain a sample of each liner batch for traceability. For museums with long-term circulation needs, a crate-to-object pairing file can record peak acceleration and humidity excursion for each journey, giving an iterative basis for improvement. Ownership of tooling, drawings and custom cradles should be explicitly agreed in contract so later duplication and maintenance are not restricted to one supplier.
Conclusion and Related Reading
An artifact case converts an open, uncontrolled journey into a closed, verifiable microclimate. Inert materials keep the cavity clean, humidity design keeps it stable, restraint keeps the object still, and records prove it. JUNZHIJIA covers rotomoulded and injection-moulded crates, inert liners, custom cradles, conditioned chambers, tooling, OEM/ODM and courier documentation.
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