cacher box
A triangular iron trough lined with wood and used for holding worked glass pieces while they await the lehr.
cacher box: holding pen for hot glass before annealing
A cacher box is a triangular iron trough, typically lined with wood or clay, that holds freshly worked glass pieces as they cool slightly before entering the lehr for annealing. The vessel sits between the hot-shop workspace and the annealing oven, serving as a thermal buffer and a work-in-progress staging area. The triangular profile allows glassmakers to stack pieces efficiently without them rolling or clustering randomly.
The iron frame provides structural rigidity to handle the weight of multiple glass items without sagging or warping. The wooden or clay lining serves two purposes: it insulates the glass from direct contact with cold iron, preventing thermal shock and surface checking, and it prevents the glass from sticking to the metal. Operators load pieces as they come hot from shaping, arranging them so air can circulate around each one and heat distributes evenly before the annealer moves them to the lehr.
The cacher box exists because moving extremely hot glass directly into a cool lehr would cause catastrophic cracking. Annealing requires a controlled temperature curve, and the lehr schedules production in batches. The cacher box allows glassmakers to keep working while waiting for lehr capacity to open up, preventing bottlenecks on the shop floor. Without it, pieces would either have to sit loose on the bench (risking damage and taking up space) or be held in the glassmaker's hands longer than is practical or safe.
Problems arise when the lining deteriorates and exposes iron, when pieces are stacked so densely that interior ones don't cool evenly, or when cold drafts reach the box and create uneven cooling on one side of a piece. A compromised wooden lining may also catch fire if ash or sparks from nearby operations fall into the box.
The name reflects the box's function: to cache, or temporarily stash, glass in a holding state. The design is simple and has remained largely unchanged for more than a century, adapted only in scale to fit different production volumes and kiln configurations.