TL;DR
Rinse an egg slicer within a minute or two of using it and always work along the wires rather than across them -- the cutting wires are thin and under tension, and side pressure from a brush or a sponge is what snaps them. Dried yolk needs a ten minute soak in cold or cool water, not hot, because heat sets egg protein harder.
Mind the wires
The wires on an egg slicer are thin enough to cut a boiled egg with almost no force, which means they will also cut skin if you drag a fingertip across them.
Never run a finger along the wire bed, and never push a sponge down onto the wires. Hold the tool by its frame and let water do the work.
If a wire has broken, its cut end is a fine point. Handle a damaged slicer carefully, and replace it -- a slicer with a missing wire produces uneven slices and the loose end can end up in food.
Keep the hinged cutting arm closed when the tool is stored, so the wires are not exposed in a drawer.
Why yolk is different from other residues
Egg is protein, and protein behaves differently from grease, starch, or sugar.
Hot water makes protein coagulate and grip harder, which is why rinsing an egg slicer under a hot tap can set the residue rather than remove it. Cold or cool water is correct for egg, just as it is for milk and blood.
Yolk in particular is a protein and fat mixture that dries into a yellow film cemented into the wire slots. That film goes hard within about fifteen minutes at room temperature.
Which means the entire technique is one of timing. Understanding which soil you are dealing with is the first move on every kitchen tool, a theme running through the guide to cleaning kitchen tools without damaging them.
How do you clean an egg slicer?
Open the hinged arm and rinse it under cool running water within a minute or two of use, directing the flow along the wires rather than across them. Wash with a little dish soap and a soft brush worked in the same direction, rinse, and air dry with the arm open.
The routine
1. Tap the egg debris out first. Open the slicer over a bin and tap the frame. Loose white falls straight out.
2. Rinse under cool running water. Hold the tool so the stream runs parallel to the wires. Water carries residue along the wire rather than pressing on it sideways.
3. Rinse the slotted base separately. The grooved bed under the wires holds crushed white and yolk in every slot.
4. Use a soft brush along the wires. If a brush is needed, stroke it in the direction the wires run. Never scrub across.
5. A little dish soap for the yolk fat. Yolk carries fat as well as protein, and a small amount of dish soap in cool water handles the film.
6. Rinse and air dry open. Leaving the arm open lets the wires and the slotted base dry. A closed slicer traps water in the slots.
Rescuing dried on yolk
If the yolk has already set, soak the whole slicer in cool or lukewarm water with a drop of dish soap for ten to fifteen minutes.
Cool water rehydrates dried protein. Hot water does the opposite, tightening the coagulated film onto the metal.
After the soak, rinse along the wires again and use a soft brush. Repeat the soak rather than increasing pressure, because pressure is what breaks wires.
For a spot lodged in a slot of the base, a wooden toothpick pushed along the slot clears it without touching the wires at all.
Can an egg slicer go in the dishwasher?
Most are labeled dishwasher safe, and dishwasher water pressure is generally gentle enough for the wires.
Two cautions. Place the slicer on the top rack, open, and secure it so it does not flip and get struck by another item -- physical impact from a heavy pan is the usual way wires break in a dishwasher. And a dishwasher's hot water sets any dried egg protein that was already present, so rinse the slicer under cool water first.
Wooden framed slicers should be hand washed only, since heat and detergent damage the wood.
Slicers with two wire beds and other designs
Some slicers cut in two directions, either with a second hinged arm or by turning the egg. Both wire beds and both frames need the same treatment.
Wedgers, which cut an egg into segments with radial blades, follow the same rules but their blades are wider and easier to brush.
Push through designs, where a plunger forces the egg through a grid, hold residue in the grid squares and need a rinse pushed through in the direction the egg travelled.
Any tool with fixed thin cutting elements is cleaned by directing water along them, never across, and the same care applies in how to clean an avocado slicer tool and to the fine wires of how to clean a whisk.
Keeping the wires intact
Do not force a cold egg. A firm, fridge cold egg puts far more strain on the wires than one at room temperature.
Do not slice anything harder than it is designed for. Egg slicers are often used for mushrooms, strawberries, and soft cheese, all of which are fine. Anything with a firm core, a pit, or a hard rind will snap a wire.
Do not press down on a stuck egg. Lift the arm and reposition instead.
Do not put pressure on the wires when cleaning. No scrubbing across, no sponges pushed into the bed, no drying with a towel pressed over the wires.
Store it closed so nothing in the drawer catches a wire.
A slicer with one broken wire is not worth repairing. They are inexpensive, and an uneven slicer with a loose wire end is a hazard rather than a tool.
Bladed kitchen tools generally need the same combination of respect for the edge and gentle cleaning, described in how to clean a pizza cutter.
Cleaning a slicer reduces residue and cross contact between foods. It is not a food safety program on its own, and eggs have their own storage and cooking rules.
Source: USDA Food Safety and Inspection Service guidance on egg handling and cleaning food contact utensils
FAQ
How do you clean dried yolk off an egg slicer?
Soak the whole slicer in cool or lukewarm water with a drop of dish soap for ten to fifteen minutes, then rinse along the wires. Do not use hot water, which sets egg protein harder. Use a wooden toothpick along the slots in the base for anything left.
Why do egg slicer wires break?
Almost always side pressure. Scrubbing across the wires with a brush or sponge, pressing a towel over them, forcing a cold firm egg through, or letting a heavy item strike them in a dishwasher all snap them. Work along the wires and let water do the cleaning.
Should you use hot or cold water on an egg slicer?
Cool or cold. Egg is protein, and hot water makes protein coagulate and grip the metal harder. This is the same reason cold water is used on milk and blood. Cool water plus a drop of dish soap handles both the protein and the yolk fat.
Can an egg slicer go in the dishwasher?
Most are dishwasher safe on the top rack, placed open and secured so nothing heavy can strike the wires. Rinse dried egg off under cool water first, because dishwasher heat sets any protein already there. Hand wash wooden framed slicers only.
How do you clean the slotted base of an egg slicer?
Rinse it separately under cool running water with the arm open, directing the flow along the length of the slots. Use a soft brush in the same direction, and push a wooden toothpick along any slot that still holds crushed white or yolk.
Is an egg slicer worth repairing if a wire breaks?
Generally not. Replacement is inexpensive, and a slicer with a missing wire produces uneven slices while the loose cut end is a hazard in food and in a drawer. Handle a broken slicer carefully, since the snapped end is a fine sharp point.
Small tools take a minute when you know the trick. The kitchen around them takes longer. If you would rather hand that off, get a quote or read more about house cleaning services.