Add a reflective custom background to a Casio F-91W

Use printable transparency film that matches your printer type. Follow the film’s instructions for the printable side and drying time. The image needs to be readable from the front when the metallic backing is behind it; check that orientation before sticking anything together.

The F-91W Background Customizer can help you arrange and size your design. Print a paper test first and compare it with your watch’s backing insert. Keep important details inside the visible display area, and print spare copies so you can retry the lamination without starting over.

Prepare the print before opening the watch, but leave final trimming until you can trace the original backing. The video uses that piece as the cutting template.

Place the watch face-down on a clean cloth. Use a correctly fitting precision screwdriver to remove the four caseback screws and put them in your tray. Lift the back gently; the gasket may stick to it.

Remove the gasket without stretching it and keep it in its original orientation. Lift out the module, then place the empty case face-down to reduce dust settling inside the crystal.

Use a small flat-head screwdriver to release the metal retaining clips around the white carrier. Slip the tip under each clip and turn slightly, using only enough movement to release it. Work around the module until the battery cover can lift away freely.

Lift off the cover and circuit board, keeping their orientation clear. Keep track of the striped rubber connector, often called the zebra strip, between the board and the LCD. It must go back clean and correctly seated for the segments to display properly.

Release the small plastic retaining tab and slide the LCD out of the carrier. Note the three dots at its edge before setting it down. Keep the original backing insert for use as a template.

With the silver backing facing you, use the tip of a fresh hobby blade to start lifting one corner of the reflector. Keep the blade nearly parallel to the surface. The goal is to lift an edge, not scrape down through the layers.

Once there is enough to grip, put the knife down and peel the reflector slowly with your fingers. Leave the rear polarising film in place. Stop if that clear layer starts coming away too, or if the glass is flexing under your grip.

The video shows isopropyl alcohol being used to remove remaining adhesive, followed by a microfibre cloth. Avoid soaking the display or letting liquid wick into its edges; check compatibility before applying a cleaner to the remaining film. Use gentle pressure and let the display dry fully before rebuilding it.

Cut a piece of metallic tape slightly larger than the finished insert. Peel off its release liner and bring the printed transparency onto the adhesive with the artwork facing the direction you checked earlier. Keep fingerprints and dust off both mating surfaces.

Press the layers together gradually, then turn the piece over and smooth the back. Work out creases without stretching the film. A fold or textured patch can show through the LCD, so use a spare print if the first attempt wrinkles badly. Assemble this insert separately from the glass; do not stick the metallic tape directly onto the LCD.

Place the original backing insert over the laminated artwork and trace its outline. Check the artwork alignment before cutting: the outline determines which part of the print will sit behind the display.

Use sharp scissors to cut along the outline, then test the piece in the white carrier. It should sit flat without curling at the edges or needing pressure to fit. Trim small amounts if needed. Keep the metallic layer within the backing area, clear of the circuit board and electrical contacts.

Place the new backing in the carrier with the artwork facing the LCD. Refit the LCD in its original orientation; the video places the three dots on the left when viewed from the front. Close the retaining tab and return the zebra strip to its channel.

Replace the circuit board and battery cover, then engage every retaining clip. Check the display before putting the module back into the case. Missing segments can mean the connector is misaligned or a clip has not seated fully.

If a reset is needed, follow the module’s AC-reset marking: briefly bridge the contact marked AC to the indicated battery-positive contact, then remove the bridge. Do not probe unmarked contacts or short the battery terminals together. A reset will not fix a misplaced zebra strip.

Use a dust blower to remove specks from the crystal and display. Remove visible smudges with a clean microfibre cloth before closing up.

Make sure the case pushers are fully outward. Lower the module into the case, guiding its spring contacts past the pushers without bending them. It should sit flat. Check all three buttons and the light before fitting the back.

Inspect the gasket and return it to its channel in the correct orientation. Replace it if damaged. Fit the caseback and start all four screws, then tighten gradually in a diagonal X pattern. Stop at snug: overtightening can damage the resin threads, and tightening cannot correct a trapped gasket.