Scope. This page provides a controlled reader-run protocol and does not claim site-run measurements. For cooking, cooling, storage and reheating, follow the current official guidance linked on the page.
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| What you have | What it is | Can you fix it |
|---|---|---|
| Milky, opaque, greyish liquid | Fat emulsified into the stock by agitation | Partly. Chill and lift the fat that separates out; the rest stays |
| Fine haze, stock still translucent | Protein broken into particles too small to settle | Only by clarifying, which costs flavour and an hour |
| Sediment on the bottom, clear above | Coagulated protein that did settle. This is normal | Yes, easily. Ladle from the top, do not pour |
| Cloudy and it tastes fine | Almost certainly nothing worth acting on | Nothing to fix |
If it tastes good, stop reading and use it. Cloudy stock is a cosmetic fault, not a flavour fault, and a great deal of cooking is built on stocks nobody ever tried to make clear.
If the clarity matters, because it is going into a consommé or a clear soup where the whole point is that you can see through it, the rest of this page explains what happened and what your realistic options are.
The two things making it cloudy
Cloudiness is light scattering off particles suspended in the liquid. In stock those particles come from two sources, and they are two different problems.
Emulsified fat. Fat rendered out of bones and meat sits on the surface if you leave it alone. Agitate the pot hard enough and that fat is broken into droplets small enough to stay dispersed through the liquid rather than rising back to the top. At that point you have made, unintentionally, a very dilute and unstable emulsion. It scatters light, it makes the stock look milky, and it changes the mouthfeel of anything you use it in.
Suspended protein. As stock heats, soluble proteins coagulate. Left in peace they clump together, and the clumps either rise as scum you can skim or sink as sediment you can decant off. Both are easy to remove. Under vigorous agitation the clumps never get to form properly: they are broken up as fast as they aggregate, and what you end up with is protein in pieces too small and too light to do anything but hang there.
Both mechanisms have the same driver, which is why they arrive together and why the advice is the same for both.
Why agitation is the variable, not heat
Here is the part that gets stated backwards almost everywhere. Cloudy stock is blamed on the stock being "too hot". Temperature is involved, but the mechanism is mechanical.
The difference in temperature between a stock held at a bare simmer and the same stock at a rolling boil is small. A boil sits at the boiling point of the liquid, which for water at standard pressure is 100°C (212°F) and drops with altitude. A bare simmer sits below that, and we give no figure for how far below; measure it in your own pot. What we can say without a probe is that it is a modest gap, because a pot cannot keep climbing past the point where its liquid turns to steam.
The difference in movement between those two states is enormous. A bare simmer moves the liquid barely at all. A rolling boil is a continuous mechanical process, with bubbles forming at the pan floor, rising the full depth of the pot, and collapsing at the surface. Every one of those is a shearing event. Repeated over hours, that is a very effective emulsifying machine, and it is doing the same job to your fat that a whisk does to oil in mayonnaise.
So the honest version of the headline is this: boiling ruins the clarity of a stock not because of the extra few degrees, but because of what the extra few degrees make the pot do. The temperature is the mechanism's trigger, and the agitation is the mechanism. This is one of four separate damages a hard boil causes, and the others are set out in why a rolling boil causes four separate problems.
The corollary is useful: anything that agitates the pot causes the same damage without a boil. Stirring a stock repeatedly does it. So does a lidded pot that traps heat until the surface starts to move, and so does a burner hot spot driving a localised roil under one part of the pan while the rest sits still. This is why "keep it below the boil" is better advice than "turn the heat down", and why the fix is about what the surface is doing rather than about a dial setting.
What a bare simmer actually looks like
Most cooks have never had one pointed out to them, which is a problem when it is the entire target. The written instruction is always some version of "simmer gently", and gently is not a description of anything.
Here is what to look for, in order of how far the pot has gone:
- Still. No movement at the surface. Steam rising. This is below a simmer, and for stock it is often exactly where you want to be.
- A bare simmer. The surface trembles rather than moves. A bubble breaks somewhere on the surface every few seconds, usually in the same spot above the hottest part of the pan floor. Nothing rises through the body of the liquid. The pieces of bone and vegetable stay where you put them.
- A simmer. A steady, gentle stream of bubbles from one or two points. The surface moves visibly. Solids shift a little. Already more movement than a stock wants.
- A rolling boil. Bubbles across the whole surface, solids tumbling, liquid turning over. This is the state that emulsifies the fat.
The test that requires no thermometer: look at a piece of vegetable near the surface. If it is moving, so is everything else, and so is the fat.
The test that requires a thermometer is better, and it is what the rest of this site exists to provide. How to find the target band for stock with a probe, rather than by description, is in stock below the simmer.
Can it be clarified after the fact?
Partly, and it depends which of the two mechanisms you are dealing with.
Fat that has been emulsified in can be partly recovered by chilling. As the stock cools, some of the dispersed fat comes out of suspension and sets on the surface where you can lift it off. How much comes back must be measured on your own setup. What we can say is that it is not all of it: a stock that went milky in the pot generally stays somewhat hazy after chilling and skimming, because the finest droplets do not separate out.
Protein haze does not respond to chilling at all. The particles are already suspended and cooling does not aggregate them.
That leaves raft clarification, and here is our honest verdict on it.
A raft works. Egg white and lean minced protein are stirred into the cold stock, the pot is brought up slowly without stirring, the mixture coagulates into a floating mat, and as it forms it traps suspended particles. You ladle the clear stock out through a hole in the raft. The technique is real, it is centuries old, and it produces genuinely clear liquid.
It also costs you:
- An hour or more, most of it attention that cannot be spent elsewhere, because the pot cannot be stirred once the raft starts forming.
- Flavour. The raft strips out aromatic compounds along with the particles. A clarified stock is cleaner and thinner in every sense. This is the trade consommé makes deliberately.
- Volume, to the raft itself and to the ladling.
- The ingredients for the raft, which is not a trivial quantity of protein used for its clarifying properties rather than its flavour.
Most home cooks should not bother. If you are making a clear soup where the transparency is the dish, do it. If you are making stock that will end up in a braise, a risotto, a sauce or a soup with things floating in it, you are spending an hour to improve something nobody will see. Make the next batch properly instead.
Getting it right next time without watching the pot
The reason people boil stock is not carelessness. It is that a pot left alone drifts upward, and nobody wants to stand in the kitchen for six hours.
Things that hold a low temperature without supervision:
- The oven. A low oven surrounds the pot with a controlled temperature rather than heating it from one point. The setting that produces a given liquid temperature under a lid is a measurement rather than a guess, and it must be measured on your own setup.
- The lid, off or ajar. A tight lid traps heat and the pot climbs. Left off, evaporation carries heat away and acts as a brake, at the cost of losing volume.
- A diffuser. Puts distance between the burner and the pan floor and removes the hot spot that starts a localised roil.
- A bigger pot than you need. More surface area, more evaporative cooling, less depth of liquid to drive convection.
- A probe left in it. The cheapest solution to the problem of not standing there. Set an alarm on the high side and go and do something else.
What does not work is turning the dial to its lowest setting and trusting it. The lowest setting on a domestic hob is a power level, not a temperature, and what it does to a full stockpot depends on the pot, the hob and the volume. That is the whole reason this site exists.
Frequently asked
Is cloudy stock a sign it has gone off? No, and do not use appearance to judge that. Clarity and safety are unrelated questions, and we do not publish safety guidance from memory. Stock below the simmer sets out what USDA FSIS publishes on cooling and storing it.
Should I skim the scum? Yes, early and often, while the coagulated protein is still large enough to lift. That protein is going to end up somewhere: either on your spoon or broken up into the liquid.
Does starting from cold water matter? It gives the soluble proteins a slow rise, which favours the large clumps that skim off easily. Whether it makes a measurable difference to final clarity in a pot held below the simmer throughout must be measured on your own setup.
Is cloudy always wrong? Not remotely. Several classic stocks and broths are deliberately cloudy, and the milky character is the point in some of them. Clarity is a specification for particular dishes, not a general standard of quality.
In Plain English
What it means. Stock goes cloudy because a boiling pot mechanically emulsifies fat into the liquid and shreds coagulating protein into particles too fine to settle. The temperature gap between a simmer and a boil is small; the difference in movement is not.
Who it helps. Anyone making stock for a clear soup, and anyone who has assumed a finer sieve would have fixed it. A sieve cannot remove particles suspended in the liquid.
When to use it. When clarity is part of the specification. Otherwise, cook with it.
What to do next. Chill it and lift the fat that sets. Ladle from the top rather than pouring. Then, next batch, aim for a surface that trembles rather than moves, and put a probe in the pot so you do not have to keep looking.
Next step
Clarity is one output of getting the stock temperature right. The others are yield, gelatine extraction and how much flavour each additional hour actually returns, which turns out to be a curve rather than a straight line.
Read stock below the simmer for how to find the target band and the hourly return, and the cited guidance on cooling and storing a large batch. The rest of the section is at everything in this section.
Related technique: Every Classic Emulsion: How To Find Its Working Range And Break Point.