By Geoff Browne, Senior Project Manager & Crating Specialist, Terry Dowd, Inc.
Art Packing and Transport: Functionally Inert and Ultralight Crates
A Functionally Inert Crate?
We were recently asked to look into the feasibility of producing crates with chemically inert interiors that could be used for the shipment and long term storage of an installation piece consisting of raw metal forms including lead, copper alloys, iron alloys, aluminum, and zinc. It has always been a goal to develop such a crate, but the projects in which these issues have come up have typically had immediate deadlines not allowing time for wide ranging research.
We have lined, gasketed, and sealed crates with various coatings, fitted them with scavenging materials, dessicants, and insulation to remove airborne pollutants and minimize the physical and chemical factors that promote reactions, and have built crates with plumbing fittings so that the atmosphere could be replaced with Helium to prevent oxidation.
My greatest concern in addressing this project was cushioning material, as I knew that urethane foams, which offer some of the best shock and vibration mitigation wouldn’t work – even the very best military grades caused slight reactions on lead and copper in prior testing and the consensus was that it could be used in storage no longer than 3 months.
Since the early ‘90s with the awareness resulting from the Art in Transit Workshops, we have endeavored to stock only archival, FDA grade, and/or commercial products considered chemically inert to help assure that we will “do no harm.” By using terms such as “chemically inert,” “FDA grade,” and “non-corrosive,” I was able to find commercial products which have since been institutionally tested and appear to be functionally inert – with 1 exception, gasketing, for which I was able to find in a FDA grade silicone product, which did pass the Standard Oddy Test, but not the Getty version of the test.
Crate Liner: Coroplast (branded, not generic) was chosen to line crate walls rather than a fabric or film due to the structural attachment link between crate wall and cushioning film via the liner and the fact that it could be precisely fitted for the best possible seal.
Sealing and adhesion of liner: Dow #748 non-corrosive silicone, and / or 3M hot melt #3748-V-O, consisting of polypropylene rather than resins.
Gasketing: Stockwell Elastomerics FDA grade silicone with acrylic adhesive – NOTE: passes only Standard Oddy Test.
Cushioning: Ethafoam 220 & M-1 (branded, made by Sealed Air Corp.)
Adhesion of Ethafoam to crate wall / liner: 3M hot melt #3748-V-O, consisting of polypropylene rather than resins.
Structural internal bracing: Polypropylene structural forms – “angle” stock, etc. – this was deemed acceptable for a prior project based on its MSDS sheet.
Next: Testing of a complete crate – stay tuned…
The Ultralight Crate
If all carriers in a transportation chain properly secure the package(s) in their respective vehicles, the greatest and most immediate risk to objects being shipped is demonstrably from human handling.
Small, lightweight packages are statistically subject to dropping from waist height, approximately 30” – 36”; as packages get heavier, they tend to be handled better and dropped from a lesser height as weight increases – a package over 250 lbs. is liable to be dropped less than a foot, and if palletized, is likely to be dropped no more than 6”.
If the package is very large and heavy but cannot be handled by typical mechanical devices and is not inherently stable, like a large and proportionately thin painting crate, the risk rises sharply – if the crate topples / falls over on one of its large faces, that rotational drop is said to be roughly equivalent to a flat drop from 2/3 the height of the crate. A hard drop onto concrete form a height of approx. 12” results in a shock of approximately 50 Gs, the threshold of damage to a typical painting in good condition – a painting in a 9 ft. tall crate that falls over would be subject to the equivalent of a 6 foot drop, resulting in a shock exponentially greater than the 50 G threshold of damage.
Aside from attaching devices such as buttress frames or the like to such a crate to make it more stable and / or possible to use mechanical devices to handle (which may inflate its size such that it cannot negotiate hallways, corners, etc.), making such crates light enough for a small number of people to lift and control may offer the best, safest alternative.
While numerous companies and institutions have tried various combinations of lightweight sheet goods to reduce crate weights – Coroplast, cardboard, cardboard honeycomb board, Foamcore, EPS insulation, etc., the combined cost of the material and / or the cost of the labor to assemble it is often beyond reach, and the final product may be structurally insufficient.
Honeycomb materials have always had great appeal, except that their cost was prohibitively high due to the fact that the sheets were handmade – until recently, when a polypropylene honeycomb core with fiberglass reinforced polyester resin skins was approved by the U.S. D.O.T. for truck body panels. Single panels can be made as large as 10 x 58 feet.
3/4" material of this type has the same strength of ½” plywood, but less than half its weight, is waterproof, floats, and has an insulation value of approx. R-4. The cost of this material is equivalent to that of a composite using cardboard honeycomb core and coroplast skins – but requires none of the labor to laminate those layers / plies and is much stronger and more stable.
A prototype crate of 30" x 36" x 12” made using this material weighs 70 lbs. vs. 98 lbs. if made using ½” MDO.
A crate of 99" x 123" x 12” made using this material would weigh approx. 240 lbs. vs. 401 lbs. if made using ½” MDO.