Glass and glazing crating

Why glass travels on edge

Glass is strong in compression along its edge and weak in bending across its face. Laid flat, a large lite sags under its own weight and cracks at a vibration. Stood on edge in a rack, it carries the load along its length, which is what the material does best.

In an A-frame crate the lites lean against a padded back rail at a small angle off vertical. The angle takes the load off the bottom edge and holds the stack back against the rail. The lower ledge is padded and the lites rest on a strip of felt or rubber, never on bare timber.

Between the lites

Lites in contact scratch or stick. Between each pair we place cork dots, paper sheets or foam strips, chosen for the coating. Low-emissivity coatings and printed ceramic frit are sensitive to rubbing, so the interleaving is picked to avoid wiping the coating.

Insulated glazing units need extra thought. Their edge seal is the weak point, so the unit is supported on the bottom edge across the setting blocks, and the stack never concentrates weight on one corner. Bundles are banded with soft straps over corner guards.

• Safety-glazed and laminated lites labelled by type
• Mirror lites separated face to back
• Tempered glass marked so it is never cut or drilled in transit handling
• Frames with glass shipped with the glass face protected by board

Edges and corners

Glass fails from the edge. A tiny chip on an edge is a crack waiting to run. Edge guards of cardboard or moulded foam go on every exposed edge, and corners get an extra cap. The bundle is wrapped in film to keep dust and spacers in place, and the top edge sits below the crate's top rail so a falling stack of crates cannot press on it.

For heavy lites, the skid runners are laid cross-wise to keep the load off a single beam, and a hardwood bearer takes the stack. We ask for the weight per lite, since a count of lites alone can mislead.

Windows, doors and framed units

A finished window or storefront unit has a frame that can bend and a glass that can pop. Units stand on their sill on a padded ledge, with the frame faces protected by board and the opening corners braced with diagonal battens, so the unit does not rack in transit.

Hardware, handles and weatherstrip are taped or boxed. Sliding panels are locked, and any operable sash is held closed with a strap over a pad. Screens ride in a separate slot, because a screen frame pressed to glass will bow.

Crate construction

The A-frame crate is built from a skid, a ledge rail, a leaning back frame and cross-braced end frames. The outer walls are open-slatted or sheathed, depending on whether the crate must be weathertight. Our A-frame crates page shows the members and how the angle is set.

A tall stack of large lites may need a strongback along the back frame so the stack does not bow. A small shipment of cut-to-size panels can go in a cleated plywood box lying on its edge, which we quote when the lites are small and the weight low.

Marks, lifting and receiving

A glass crate must be lifted with the A on top and the rail down. ISO 780 symbols for fragile and this way up go on all sides, with a glass pictogram and a bold arrow showing which edge is the base. Forklift entry is on the long side of the skid, with a mark showing where forks go.

A tip indicator and a shock indicator are fitted on the end panel. The receiver should unload with a forklift or crane and never roll the crate on its end, and should read the indicators and photograph the crate before breaking the bands.

Export and site delivery

Export crates use heat-treated lumber with the IPPC stamp. Glass crates sometimes stay on site as a storage rack, so we make them from stamped lumber and leave the lid screwed rather than nailed. The crate spec stays on file so a repeat glazing order is built to the same dimensions.

Curved, laminated and oversized lites

Bent glass has no flat edge to stand on. We build a cradle matched to the curve, with contoured foam, so the bent lite is supported along its whole line. Laminated lites are heavy for their size, so the skid and the strapping are sized to the gross weight rather than to the face area.

Oversized lites may exceed what an A-frame crate can safely carry. In that case a long crate with a rigid back and a protected edge rail is built to the length, and the load plan is agreed with the carrier before the order is placed.