Sprayfoam cavity fill... a thing?

Hi everybody. I have a prospective oversized crating job coming up, exterior dimensions in the ballpark of 7'x9'x8'. It will initially house a roughly 400 lb. plaster cast of three human figures, travel quite literally across Canada from Nova Scotia to a foundry in British Columbia, and the resulting bronze sculpture - having beefed-up to anywhere from 500-700 lbs. - is supposed to climb back into the same crate, and come back to Nova Scotia.

I am most concerned about the outgoing plaster cast. This job just popped on the radar, and as I have not yet seen the actual piece, I am imagining a lot of foam-wrapped wood and custom-made armatures at important junctures all over, to make sure the cast stays in one piece and arrives with all its limbs and digits.

What I love is the idea of wrapping the piece in plastic, setting it on its base inside the crate, and sprayfoaming the cavity to capacity, then flush-cutting the foam, attaching the crate face, and off it goes as a solid cavity fill. Some extra packing on the other end could make up for the difference in size between the plaster cast and the finished bronze, and the return journey would be a much less fussy packing experience, I imagine, having to deal mostly with just the weight, more than any concern that an arm is going to snap off?

Pretending for a moment that budget would not be a restriction, I am wondering if the spray-foam cavity pack is a legitimate practice for object crating? Open-cell 2lb. foam? Closed cell 4lb.? Have any of you done this before?

Thanks for any input and thoughts!

BEN

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Originally Posted by benjamin_wooten

Hi everybody. I have a prospective oversized crating job coming up, exterior dimensions in the ballpark of 7'x9'x8'. It will initially house a roughly 400 lb. plaster cast of three human figures, travel quite literally across Canada from Nova Scotia to a foundry in British Columbia, and the resulting bronze sculpture - having beefed-up to anywhere from 500-700 lbs. - is supposed to climb back into the same crate, and come back to Nova Scotia.

I am most concerned about the outgoing plaster cast. This job just popped on the radar, and as I have not yet seen the actual piece, I am imagining a lot of foam-wrapped wood and custom-made armatures at important junctures all over, to make sure the cast stays in one piece and arrives with all its limbs and digits.

What I love is the idea of wrapping the piece in plastic, setting it on its base inside the crate, and sprayfoaming the cavity to capacity, then flush-cutting the foam, attaching the crate face, and off it goes as a solid cavity fill. Some extra packing on the other end could make up for the difference in size between the plaster cast and the finished bronze, and the return journey would be a much less fussy packing experience, I imagine, having to deal mostly with just the weight, more than any concern that an arm is going to snap off?

Pretending for a moment that budget would not be a restriction, I am wondering if the spray-foam cavity pack is a legitimate practice for object crating? Open-cell 2lb. foam? Closed cell 4lb.? Have any of you done this before?

Thanks for any input and thoughts!

BEN

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Hi Ben,

I will wade in and try to be of help.
Not having seen the artwork it is very hard to be accurate but if it is a sculpture of 3 figures you may not want to use expansion foam. Aside from it being very unpleasant and toxic, expansion foam can "lock up" a complex sculpture by surrounding its forms. It would then have to be cut away very carefully and not re-used. Unless you have an 8 foot hot wire knife, flush cutting the foam at the front of the crate will be messy and difficult.
8 feet by 9 feet is a big foot print. If the base is that large then 2 lb ethafoam should be fine for support under the 400 or 700 lb artwork. To lessen shock you could put 2" of 1.4 lb grey polyurethane foam under the 2" of 2 lb. ethafoam. Brace as you described above using foam padded braces. Keep the bracing simple. If a breakable artwork is braced to too many points then any torquing of the crate can damage the piece.
Finally, use Air-Ride transport. A plaster form should be able survive the trip using this method.

Regards

Steve Spargur
General Manager
L. A. Packing, Crating and Transport Inc

Hi Ben,

I once had a vendor come to the museum to demonstrate expandable foam packages. The packages contained the foam components and you ruptured them, then let them expand around your object in its crate. Our collections were mainly two dimensional so we didn't try the product.

I would worry about undercuts, negative spaces and such on the sculpture and wonder if it could be done in sections like you were making a mold? Maybe the foam could be sprayed into packages, like a heavy duty leaf bag, which then expands around parts, but is removable. You may not be able to save and reuse the sections for the return trip however unless they were somehow marked. An experiment may be in order.

Jim Meeks
Curator of Exhibits
OK History Center

I found a box in a storage area with some electronics parts or something and lo and behold there were foam packages inside and the brand is Instapak Sealed Air.

We see this method a lot on welded aluminum frames from Smallcorp, a great vendor here in Massachusetts that I'm sure some of you are familiar with. As mentioned, Sealed Air has a system of foam and corresponding bags for this kind of packing. It's very clever and effective for something like a welded frame, that's strong and has regular edges; the bags go in the corners of the box, foam goes in bags and expands around frame, done deal.

I'd have to agree though, that it would difficult to use for the complex form you describe; if you did want to pursue spray foam packing, approach it with an exit strategy in mind and use smaller bags of foam at strategic points. The traditional padded brace method might be simpler.

Of note re: the leaf bag comment, and my own DIY experiments with spray foam packing: regular insulation spray foam will NOT CURE if enclosed in high density poly. You end up with a horrible goopy chemical mess. I'm not sure the recipe Sealed Air uses to make their system work, but the bags they use look like an LDPE.

Some good suggestions above, but I thought I would chime in on using the expandable foam packages that work by rupturing a component within the bag. I was packing a shipping container that would be loaded on a container ship and cross the Atlantic. The shipment consisted of consumer goods and proto-types packed in crates. After caulking the holes in the container we loaded the crates and used cheap ratchet straps and boards screwed to the floor of the container to lock the load. I also had a bunch of the foam bags that I planned to use as a secondary measure to secure the crates. I had several bags expand with enough force to move a 100 kilo crate a couple of inches as I was placing them between the crates and the outer wall of the container and in between crates!

I didn't catch this when originally posted. I think it is an interesting notion that HDPE vs LDPE effects the cure or cure rate. I wonder if anyone would be willing to research this?

Interesting observation. Some old comments about using the expanding urethane foam in spray is the degree of expansion that can take place and the potential for pressure being exerted on fragile objects. The notion at one time was that this phenomenon was present relative to the size of the fill. Suggested solution was to fill the void partially and allow it to cure and then add more to complete the fill. Of course the other point of discussion is that products can continue to expand for quite a while after mixing (spraying). The other obvious issues are those of material off-gassing, and the intitial rise in temperature that results from the chemical reaction that forms the foam. I would love to hear from an expert in this particular material.

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