Five Steps to Safe Shipment – Canadian Conservation Institute (CCI) Notes 20/3

Disclaimer

The information in this document is based on the current understanding of the issues presented. It does not necessarily apply in all situations, nor do any represented activitiesssssss ensure complete protection as described. Although reasonable efforts have been made to ensure that the information is accurate and up to date, the publisher, the Canadian Conservation Institute (CCI), does not provide any guarantee with respect to this information, nor does it assume any liability for any loss, claim or demand arising directly or indirectly from any use of or reliance upon the information. CCI does not endorse or make any representations about any products, services or materials detailed in this document or on external websites referenced in this document; these products, services or materials are, therefore, used at your own risk.

List of abbreviations
A
area
h
height
LDPE
low-density polyethylene
RH
relative humidity
t
thickness
W
weight

Introduction

This Note outlines a five-step approach to packing fragile objects for shipment. The steps describe some of the key actions to take to help ensure that objects arrive at their destinations safely.

When shipping a fragile object, the main concerns will be

Step 1: begin with object features and shipping details

It helps to start the packing project by asking questions such as the following:

The answers to these questions will help you plan your shipment and establish appropriate packaging requirements.

Advise your carrier if there is anything unusual about the object being shipped or the shipping specifications. Basic package design information, such as object size and weight, helps in selecting the right vehicle; it also makes it easier to estimate the package size to ensure that it can move easily through shipping and receiving sites. Information on the object and its materials will help to prioritize hazards and necessary control measures.

Insights gained from people familiar with the object can help to specify handling methods and the design of suitable packaging, especially where handling forces or package features come in contact with the object. This dialogue may also aid in the discovery of unusual or hidden object susceptibility. If objects are shipped for treatment, they may require protective measures (such as consolidating loose paint). In this case, seek conservation advice in advance.

The time of year and the amount of time in transit will indicate whether or not temperature-controlled transport is needed. Typical packaging provides anywhere from 30 minutes to several hours of protection against sudden temperature changes. When temperature-controlled transport is required, the standard specification is reliable control in the range of 15°C to 25°C (59°F to 77°F).

The type of shipment will help inform a package concept. A one-way source-to-destination shipment can be packed simply (for example, basic screw closures for shipping crates). If packing for multiple venues, you can include features that simplify repeated crating and uncrating cycles.

To ensure safe shipment, anticipate the hazards on the toughest leg of the journey and pack accordingly. Table 1 summarizes several shipping network scenarios and compares their hazard profiles. Some packaging comments are offered for basic guidance. Because object susceptibility and museum package performance are often unknown, consider additional actions you can take to ensure safe shipment. They include good planning and oversight, ensuring that cargo is well secured in the transport vehicle and using good carriers and well-maintained transport vehicles.

Table 1: several distribution network scenarios, their handling hazard profiles and how to address them
Scenario Relative hazard intensity Packaging comments
Art handler door-to-door shipment without cargo transfers (controlled network) Low
  • Primary packaging alone may offer adequate protection.
  • Lighter crating options may be considered.
  • Basic cushioning is 25 cm (1 in.) thick. Use 50-mm (2-in.) thick cushions for items of high value, high importance or high fragility.
Art handler shipment and supervised air cargo Low to moderate
  • Provide moderate cushioning, such as a basic wrap up to 50 mm (2 in.) thick.
  • Lighter crating options may suffice. Ensure adequate crate durability for truck transport to and from the airport.
Art handler shipment, air cargo and trusted commercial carriers Moderate
  • Assume higher and more frequent drops.
  • Use a cushion thickness of 50 mm (2 in).
  • Use more durable shipping containers or crates.
  • Anticipate moderate hazards during cargo transfers.
Commercial carriers Moderate to high
  • Use durable crating with at least 50 mm (2 in.) of cushioning. Crates should be built according to recognized standards (ASTM, military or other organizations for domestic and overseas shipment).
  • Anticipate typical drop hazards for commercial shipments.
Parcel post courier shipments High to very high
  • This is the highest hazard network for small to medium-sized packages. Anticipate drops from heights of up to 2 m (6.5 ft.).
  • A cushion thickness of 100 mm (4 in.) or more may be required.
Table 2: methods to prevent typical causes of damage during handling and transport
Factor How it causes damage Remedies
Fundamental problems
  • Collision of loose objects inside the package or collision between object parts that can move
  • Bending or deformation of packaged items
  • Abrasion between moving objects or object parts
  • Crates that fall apart, spill their contents or deform
  • Other secondary effects of motion induced by package reorientation, shock or transport vibration
  • Use mounts and partitions to prevent collisions.
  • Support objects on mounts or fixtures to prevent bending or deformation.
  • Use fixtures, mounts, protective wrapping and soft cushions to prevent abrasions.
  • Find or build crates with performance-based construction details.
Excessive force
  • Shock or vibration that exceeds damage thresholds
  • Vibration amplification (resonance) in objects or their parts
  • Shock amplification in loose parts and assemblies
  • Reduce object susceptibility to forces (consult Step 2).
  • Select and use cushioning material correctly.
  • Isolate the vibration with cushioning.
Lack of restraint in transit
  • Repetitive bouncing of cargo
  • Items fall off stacks in moving vehicles
  • Secure loose cargo in transport vehicles.
Environmental hazards
  • Extreme heat or cold
  • RH extremes
  • Water contact (rain, snow)
  • Pests
  • Pollutants (chemical effects from packaging materials)
  • Specify temperature-controlled vehicles.
  • Use crates with good detailing (tight joints, close-fitting covers, etc.).
  • Use appropriate materials.
  • Insulate crates.
  • Wrap RH-sensitive items.
Extreme hazards
  • Intentional mishandling of packages
  • Major vehicle accidents
  • Choose reputable carriers and handlers.

Step 2: reduce object susceptibility, if possible

The susceptibility of an object or its parts to damage by shock or vibration increases with the degree of flexibility and looseness, the presence of structural or material weaknesses and any pre-existing damage. In some cases, it may be possible to reduce susceptibility by controlling these factors. Table 3 lists several examples and suggested remedial measures.

Table 3: examples of object susceptibility and possible remedies
Example Remedies
Out-of-plane displacement (bowing out of the canvas perpendicular to its plane) of small to medium-sized canvas paintings
Out-of-plane displacement of a large canvas
Forces causing weak painting frames or stretcher boards to scissor (deform) and increase strain levels in a stretched canvas
  • Backing boards (consult CCI Note 10/10 Backing Boards for Paintings on Canvas)
  • Durable display or transport frames
  • Stretcher linings
  • Transit frames
  • HTS (handling-transportation-storage) frames
Fragile paint layers in a painting being shipped for treatment
  • Consolidation for shipment (consult a conservator)
Minimize factors that increase force susceptibility in large items, such as furniture and machinery
  • Connectors and attachments are secure
  • Travel orientation may help reduce force effects (for example, ship a table with weak legs upside down and adequately supported)
  • Blocking or bracing provisions on transit structures for shipment
Pre-existing damage
  • Primary packaging that prevents bending or deformation of damaged features, combined with good cushioning
Complex assembly (such as a dinosaur skeleton or a contemporary art item)
  • Disassembly, if feasible (The individual parts of an item are often less fragile than the assembled whole.)
  • Gentle restraint of loose vibration-prone or weakly attached items

Step 3: achieve important benefits with primary packaging

Primary packaging is basic protection that is applied close to or in contact with the object. This may include wrapping, protective interleaves between objects, and transit mounts that firmly restrain an object in all directions. Primary packaging can make objects easier to handle and pack, and it may provide adequate protection on its own in some cases. It can also be used to control environmental hazards for susceptible items. Table 4 provides examples of primary packaging treatments and their benefits.

Table 4: primary packaging contributions to package effectiveness
Primary packaging treatment Benefits
Basic wrapping with an interleaf material followed by polyethylene (wrapping paintings, as outlined in CCI Note 10/16 Wrapping a Painting)
  • It prevents punctures, dents and abrasion and protects against minor impacts.
  • It protects against dust, pollutants and insects.
  • It contains the object as well as possible pests for inspection and/or treatment.
  • Polyethylene wrapping allows objects to self-buffer if sufficient hygroscopic material is enclosed.
Armatures or other provisions to support a fragile object or one with fragile surfaces at non-critical areas
  • It provides an intermediate structure or object shape that is easy to cushion.
  • It prevents direct contact between the fragile object surfaces and the cushioning material.
Careful, repetitive wrapping of an object with a fragile surface with narrow strips of unbuffered tissue paper made of abaca fibres, also known as a “mummy wrap”
  • It protects a fragile surface, enabling the object to be cushioned directly (not recommended for paintings).

Negative mount (a form-fitting cut-out in a firm foam material such as polyethylene foam) or a padded wooden armature

(An interleave material may be used between the object and the mount to improve the fit of the mount or to further protect fragile surfaces at support locations.)

  • It minimizes the load per unit area on fragile object surfaces.
  • Voids can be carved around small projections prone to damage when packing or unpacking.
  • Floating a firm object/mount combination on a soft cushioning system prevents movement along the object/mount interface.
Hard objects such as bottles or dishes packed together in a box and separated from each other and the inner box surfaces with an interleave material such as cardboard, foam, tissue, cellulose wadding or paper
  • It prevents impact between hard objects and the damage caused at very low force levels.
Measures to ensure that the items do not move or collide with each other, such as several items firmly packed and separated with suitable interleaves or durable partitions for heavy items
  • It protects multiple items with a single cushioning system.
  • Cushion design is simplified.
  • It provides better assurance of good cushion performance.
  • It allows for economical use of expensive cushioning material.
Filling internal voids of thin-walled items such as hats or boxes
  • It helps items retain their shape during shipment and can help prevent object movement (for example, void filling in a teapot handle).
Table 5: a collection of primary packaging materials with their applications
Material Description Applications
High-density polyethylene sheet (HDPE)
  • Higher density than ordinary polyethylene sheet and a better moisture barrier than LDPE with thinner films
  • Flexible and soft
  • Few release agents and plasticizers
  • Available as small food-grade bags or in larger rolls from bag manufacturers
  • Wrapping
  • Protective covering
Low-density polyethylene sheet (LDPE)
  • Chemically stable
  • Talc or other release agents may be present and surface may also have an oily residue
  • Wrapping (with an interleaf material between the polyethylene and the painting)
  • Wrapping inner boxes
Thread seal tape made of poly(tetrafluoroethylene) (Teflon)
  • Synthetic fluoropolymer
  • Chemically stable, non-toxic
  • Very stretchable and able to conform to various shapes
  • Non-abrasive interleave for light objects with fragile surfaces
  • Use over polyester batting to form pads
Aluminum-coated polyethylene (such as Marvelseal 360)
  • Nylon-coated aluminum barrier bonded to polyethylene
  • Effectively blocks moisture, gases and pollutants for long periods of time
  • Lining shipping crate interiors, especially for long storage periods
  • Bags are used to encapsulate objects with desiccant and to maintain low humidity during storage
  • Lining inside surfaces of interior boxes of double case packages
Unbuffered tissue paper
  • Unbuffered long-fibred tissues made from abaca fibres, similar to Japanese paper
  • Expensive
  • Cushion very delicate materials and as an interleave on delicate items to conform with intricate surfaces and shapes
  • Mummy wrap objects with fragile surfaces by repeatedly wrapping the item with thin strips of this material
Non-woven polyethylene sheets (such as Tyvek)
  • Spun-bonded high-density polyethylene fibres woven into a fabric
  • Lightweight, chemically stable, non-abrasive and tear-resistant
  • Interleave material for contouring foam pads
  • Heat-weldable to itself, or it can be sewn
Cross-linked polyethylene sheet (such as Volara)
  • Very smooth and non-abrading
  • Common density is 33 kg/m3 (2.2 lb./ft.3)
  • Thickness range: 3–12 mm (1/8–1/2 in.)
  • A commonly used thickness is 6 mm (1/4 in.)
  • Provides a non-abrasive surface at contact points
  • Lining boxes and crates
  • Padding for small unframed paintings in transit frames
Stretch wrap
  • Linear low-density polyethylene (LLDPE)
  • Flexible and elongates to wrap around shapes
  • Best used with a barrier material
  • Comes in roll widths of 50 mm to 760 mm (2 in. to 30 in.)
  • Obtained from moving or packing material supply outlets
  • Holding delicate objects or object parts in place
  • Secure boxes together
  • Seal packages against moisture, pests, etc.
Polyethylene foam sheet (such as Ethafoam and PolyPlank)
  • Chemically stable closed-cell polyethylene foam
  • Easy to work with
  • Typical density is 33 kg/m3 (2 lb./ft.3)
  • Typical thickness is 50 mm (2 in.)
  • Long-term storage mounts and transit mounts
  • Can be heat-welded to itself
Acid-free tissue, unbuffered
  • Acid-free tissue not containing lignin made from high-quality pulp
  • Enclose with object when wrapping to stabilize humidity and avoid condensation
  • Void filling, stabilizing objects in mounts
Polyester quilt batting
  • Sold in rolls to make quilts
  • Can be layered
  • Padding uneven or complex surfaces
Extruded polystyrene foam plank (such as Styrofoam)
  • Non-resilient (does not return to its original shape after impact)
  • Excellent insulator
  • Chemically stable
  • Mounts and supports for heavy items
  • Thermal insulation
  • Apply to the inner surface of an inner case in a double case system or to the inner surface of a shipping crate

Step 4: use protective cushioning effectively

Protective cushioning provides consistent protection on all sides of an object. It is easy to apply to items that have simple shapes and durable flat surfaces. The challenges of cushioning objects with complex shapes or fragile surfaces can be addressed with mounts, fixtures or a double case system. Cushioning methods for several object types are described in Table 6.

Table 6: how to cushion items with irregular shapes or fragile surfaces
Object Cushioning method
Unframed painting structure that is weak and susceptible to deformation Add a travel frame that provides reinforcement and flat durable surfaces for cushion application (consult CCI Note 10/16 Wrapping a Painting).
Delicate ornate frame Securely mount the frame inside an HTS frame and apply cushioning to the frame surfaces (consult CCI Note 10/16 Wrapping a Painting).
Fragile pottery item with projections Use a negative mount that has voids carved around the small projections. This mount can then be cushioned or placed in a cushioned inner case.
Several fragile items that will be shipped together Pack the items into the inner case of a double case system with suitable interleaves or mounts. Use durable partitions for heavy items.

Cushioning can be achieved in a number of ways. This Note considers typical cushioning methods that include wrapping in resilient material such as bubble pack and the use of foam cushioning material.

© Government of Canada, Canadian Conservation Institute. CCI 132906-0001
Figure 1. Pad layouts for several object shapes using foam sheet material. Objects can also be cushioned by using simple wrapping and padding methods, with attention paid to the load imposed on the cushioning material.

To verify that a material is being used correctly, divide the total weight (W) supported by the cushioning material by the area (A) of cushion coverage. Do this on each side if the coverage is different. If the result is within the load range shown in Table 7, the material is being used correctly; this means that the object can deflect into the cushioning but is not at risk of bottoming out. If the result is outside the range, adjust the coverage (increase or decrease A) or select a different material. Data regarding additional materials can be found in Technical Bulletin 34 Features of Effective Packaging and Transport for Artwork and in other references cited in the Bibliography, and it can be obtained directly from manufacturers.

Polyurethane ester foam is a good choice for cushioning. It is highly efficient, but it should not be placed in direct contact with object surfaces.

Polyethylene foam is chemically stable and easy to carve, making it a popular choice for mount-making applications. It is also a good cushioning material for heavy or moderately heavy objects.

Adequate thickness is an important feature of effective cushioning. As a general guide, cushioning should be at least 50 mm (2 in.) thick. For fragile items shipped through high hazard networks, a cushion thickness of up to 75 mm (3 in.) or 100 mm (4 in.) may be necessary.

Further to the basic cushioning advice provided here, CCI Note 20/2 Foam Corner Pads provides a list of pre-designed pads. CCI’s web-based cushion design calculator PadCAD is also freely available. This online tool applies cushion design methods used in commercial packaging and only requires basic information on the object, the shipping hazard and the desired cushion layout.

For effective shock and vibration isolation, everything that floats on the cushioning should be reasonably firm. The protected item should move on its cushioning with relative ease and behave as a single unit without any secondary movement of its own. The cushioning system should be the most flexible part of the protective package.

Table 7: applications for several commonly used cushioning materials and accompanying information
Material Description Applications Typical load range for cushioning (W/A)
Polyurethane ester
  • Usually dark grey, having an open-cell structure
  • The most common density and thickness used are 33 kg/m3 (2 lb./ft.3) and 50 mm (2 in.)
  • Does not go by a trade name
  • Avoid direct contact with metals or other object surfaces
  • Protective cushions
  • Good choice for cushioning double case packages
  • SI: 0.003–0.06 kg/cm2
  • Imperial: 0.04–0.8 lb./in.2
Polyethylene
  • White closed-cell polyethylene foam
  • Chemically stable
  • Most commonly used density and thickness is 33 kg/m3 (2 lb./ft.3) and 50 mm (2 in.)
  • Thermoplastic, heat-weldable to itself
  • Excellent choice for mount-making due to chemical stability
  • Easy to work with
  • Also used for cushioning heavier items
  • SI: 0.015–0.1 kg/cm2
  • Imperial: 0.2–2.0 lb./in.2
Bubble pack
  • Air-encapsulated film
  • Use with an interleaf material to avoid contact with chemical release agents
  • Use a thickness of at least 50 mm (2 in.) on all sides
  • Lightweight materials with simple or complex shapes and durable surfaces
  • Avoid direct contact with object surfaces such as metal due to possible staining by chemical release agents
  • Use standard bubble sheet for items less than 2 kg (5 lb.)
  • Use heavy-duty bubble pack for items weighing up to 18 kg (40 lb.)

Step 5: find or construct appropriate shipping crates

The shipping crate is the first line of defence against shipping hazards. Lightweight crates may be suitable in controlled networks, but greater durability may be necessary in common shipping networks.

Light crating options include corrugated mirror boxes, triwall containers (consult CCI Note 1/4 Making Triwall Containers) and channel crates (consult CCI Note 20/1 The CCI Channel Crate: Making a Lightweight, Reusable Crating System). Wood crate specifications for domestic or overseas shipment of items weighing up to 454 kg (1000 lb.) are available as published standards.Footnote 1.

The minimum crate panel thickness in published standards is 9.5 mm (3/8 in.). In museum practice, 12 mm (1/2 in.) is a typical minimum thickness because the panels are flatter and easier to work with and there is not much difference in cost.

© Government of Canada, Canadian Conservation Institute. CCI 132906-0002
Figure 2. Three container options, clockwise from top left: a triwall container case, a CCI channel crate and two versions of an ASTM D6251 plywood crate.

Handles and skids will make it easier to move larger crates by manual and mechanical means. Careful handle positioning can reduce drop hazards by minimizing the height to which a package is raised during manual handling. Knee height is a good general guide for handle placement.

Table 8: three crating alternatives for in-house construction
Crate type Description Applications
Triwall container
  • Lightweight, but strong
  • Triple-wall corrugated cardboard with softwood framing
  • Can be constructed in as little as 20 minutes
  • Local moves, long-distance moves with high-quality transport
CCI channel crate
  • Lightweight, strong and reusable
  • Breaks down for low-cost return shipment and compact storage
  • Paintings or other objects in controlled shipping networks

Basic shipping crate (such as ASTM D6251)

  • Plywood (sanded on one or two sides) with a thickness of 9 mm, 12 mm or 18 mm (3/8 in., 1/2 in. or 3/4 in.) and 19 mm × 64 mm (1 in. × 3 in.) or 19 mm × 80 mm (1 in. × 4 in.) cleats (framing)
  • The base design can be modified for different access options
  • Handles and skids may also be added
  • A strong case suitable for domestic and international shipment
  • Loads up to 450 kg (1000 lb.)

Note that pest control regulations apply to all wood packaging material greater than 6 mm (1/4 in.) thick that is shipped to international destinations. This includes shipments between Canada and the U.S. At the time of writing, manufactured woods such as plywood, particleboard and waferboard were not subject to regulation. For up-to-date information on applicable regulations, consult the Canadian Food Inspection Agency, which administers the Canadian Wood Packaging Certification Program.

If objects are wrapped (in polyethylene, for example) and will not be stored in the case for long periods, they will be protected against contaminants. Thus, the case interior may be left unfinished. However, good construction detailing is still necessary to prevent the ingress of moisture and pests.

Applying a barrier to the inside surface of a wooden shipping crate can offer the following advantages:

Aluminum-coated polyethylene (Marvelseal 360) is highly effective as a moisture and pollutant barrier and offers a low-friction surface. A lower cost alternative to Marvelseal is to paint the case interior. However, performance is also lower. Painting is advisable if the case contents will be stored inside for long periods. The following paints are suitable for this purpose and will need to dry thoroughly (four weeks is recommended) before the case is used:

Any paint or coating can be applied to the exterior of the shipping case. For the interior, some paints and coatings should never be used, as they give off compounds that could react with object materials. These include:

Features of a good crate

© Government of Canada, Canadian Conservation Institute. CCI 132906-0003
Figure 3. Pump truck dimensions to consider for large or heavy crates: distance between tines for standard and narrow pump trucks, typical tine width and typical raised height.

Final comments

The basic information provided in this Note can help provide more assurance of safe shipment for fragile items. For more detailed information on this topic, consult Technical Bulletin 34 Features of Effective Packaging and Transport for Artwork and the publications listed in the Bibliography. CCI also welcomes direct client enquiries about packaging problems and is happy to offer assistance.

Bibliography

Barclay, R., A. Bergeron and C. Dignard. Mount-making for Museum Objects, 2nd ed. Ottawa, ON: Canadian Conservation Institute, 2002.

Daly Hartin, D. Backing Boards for Paintings on Canvas, revised. CCI Notes 10/10. Ottawa, ON: Canadian Conservation Institute, 2017.

Marcon, P. Features of Effective Packaging and Transport for Artwork. Technical Bulletin 34. Ottawa, ON: Canadian Conservation Institute, 2020.

Marcon, P. Foam Corner Pads. CCI Notes 20/2. Ottawa, ON: Canadian Conservation Institute, 2021.

McKay, H., R. Arnold, W. Baker and D. Daly Hartin. Paintings: Considerations Prior to Travel, revised. CCI Notes 10/15. Ottawa, ON: Canadian Conservation Institute, 2015.

McKay, H., A. Morrow, C. Stewart, W. Baker and D. Daly Hartin. Wrapping a Painting, revised. CCI Notes 10/16. Ottawa, ON: Canadian Conservation Institute, 2015.

Mecklenburg, M.F. Art in Transit: Studies in the Transport of Paintings. Washington, D.C.: National Gallery of Art, 1991.

Schlichting, C. Working with Polyethylene Foam and Fluted Plastic Sheet. Technical Bulletin 14. Ottawa, ON: Canadian Conservation Institute, 1994.

Snutch, D., and P. Marcon. Making Triwall Containers. CCI Notes 1/4. Ottawa, ON: Canadian Conservation Institute, 1997.

Further reading

The Wooden Crates Organization. Box and crate standards. N.p.: Deploy Tech Services, LLC., 2020.


By Paul Marcon

© Government of Canada, Canadian Conservation Institute, 2021

Cat. No.: NM95-57/20-3-2021E-PDF
ISSN 1928-1455
ISBN 978-0-660-38050-6

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