A slick of oil sitting on top of egg and vinegar, no matter how long you whisk it, was never an emulsion to begin with — it's raw ingredients that missed the one narrow window where a base actually forms. That's a different failure than a sauce that thickened and then split later, and it's fixable almost every time: whisk a fresh base in a clean bowl, then feed the ruined mixture into it the way you'd feed in oil.
Never Formed Is a Different Failure Than Broken
Two very different things get called "my mayonnaise broke." One is a sauce that thickened, held for a while, and then let go — droplets that were coated and suspended found each other again and recombined into visible globules. The other is a sauce that never crossed over in the first place. Oil and the egg-vinegar base sat next to each other through the whole process, and whisking harder didn't change that. The first is a coating that failed. The second never had a coating to fail, because nothing was ever suspended fine enough to need one.
Why the Whisk Can't Do Anything Before There's a Base
A whisk breaks oil into droplets through shear — dragging one fluid against another fast enough to tear it apart rather than just push it aside. Shear works on a thick fluid. It barely works on a thin one, because a thin liquid just flows out of the way instead of resisting and tearing. Egg yolk and vinegar on their own, before any oil has gone in, are thin. So the first few drops of oil are the hardest part of the whole process, and not because the ratio is wrong. There isn't yet a viscous, half-emulsified pool for the whisk to grip.
Once that first small pool exists — a spoonful of oil fully worked into the yolk — it's noticeably thicker, and the whisk suddenly has body to shear against. Everything that follows depends on protecting that. Add oil faster than the pool can absorb it, even at this early stage, and the whisk goes back to shearing thin liquid. That does nothing, no matter how long you keep at it.
The Six Ways the Base Never Gets Built
| What happened | Why it stops the base from forming |
|---|---|
| Oil poured in a stream from the very first drop | There's no thick pool yet for the whisk to shear against, so the oil just pools on top instead of breaking into droplets. |
| Too little continuous phase for the oil you're using | Even perfect technique can't disperse fat into a base too small to hold it — the ratio makes it a mechanical impossibility, not a skill problem. |
| A bowl too wide and shallow for the volume in it | The mixture spreads into a thin layer the whisk skims across instead of working through, so it never builds real shear. |
| Immersion blender head not sealed against the bottom, or lifted before the base sets | The high-shear zone at the blade sits in bulk oil instead of against the yolk beneath it, so a fine base never gets the chance to form. |
| Cold egg and cold oil | Both are more viscous than at room temperature, and a whisk supplies a fixed amount of force — against stiffer fluid, the same motion tears fewer, coarser droplets. |
| Not enough emulsifier for the amount of fat | The yolk or mustard runs out of coating capacity before the oil runs out, so a stable droplet population is never physically possible at that ratio. |
How to Restart It
Whisk a fresh continuous phase — a new egg yolk, or a spoonful of water and mustard — alone in a clean bowl. Work it until it has some body of its own, thick enough to visibly coat the whisk. Then treat the entire failed batch as if it were the oil: add it back in slowly, a little at a time, letting each addition get absorbed before the next. Nothing in the failed mixture is spoiled. The oil is still oil and the yolk is still yolk; they just never got the chance to combine the first time.
What It Looks Like When the Base Finally Catches
Watch the color and feel the resistance. A base that has caught turns from streaky and translucent to a uniform, pale, opaque color within a few seconds of the first oil going in — there's no gradual fade, it's a visible switch. At the same moment, the whisk stops gliding through thin liquid and starts dragging against something with actual body. That resistance is the signal to speed up, not slow down. If a few strokes go by and the mixture still looks glassy and the whisk still moves without any drag, the base hasn't formed yet, and adding more oil on top of it will only make the eventual restart bigger.