Hot Splice

The hot splice works on a principle fundamentally different from cold splices: two film ends are welded together by precisely applied heat and pressure. The process melts the cellulose base and emulsion layers in a controlled manner so that they merge into each other—a mechanical fusion rather than a chemical adhesive. On set and in the editing suite, you'll need this technique when working with positive prints or intermediate negatives. For raw stock and original negatives: hands off. The heat would damage the emulsion.

The practical advantage lies in speed and durability. A hot splice joins two ends in seconds—the splice is immediately ready for use, with no waiting time like with chemical splices that need to cure. The joint is more solid, more elastic, and does not warp with age. This is crucial for release prints that run through the projector multiple times, or for work prints that are heavily edited. You can recognize a well-made hot splice by the uniform, transparent seam—no tears, no bubbles in the material.

Handling requires experience. The film ends must fit together precisely—not overlapping like a cold splice, but butting up against each other. Too much heat burns the layer; too little won't hold. Professionals work with digital temperature controls and defined pressing times (usually 0.5 to 2 seconds at 140–160°C, depending on the film type). This works reliably with black-and-white positives and color internegatives. However, as soon as original color material is involved, editors switch to the cold splice or wet-gate method—the risk of heat damage is too great. A fused original is lost.

In the digital age, the hot splice has lost some of its importance—but those still working with 35mm film continue to use it for final materials and for TV broadcast versions. The hot splice is part of the basic manual equipment of every professional editing suite working with positive film.