How do I fix lumpy gravy?

Why lumps form, the two ways to remove them, and the method that prevents them entirely.

Difficulty: beginner
Time: 15 min
Read: 2 min

Short answer

Sieve it, or use a stick blender. Lumps form when flour meets hot liquid all at once, so the fix next time is to make a slurry with cold liquid or to cook a proper roux first.

Gravy lumps are dry flour with a cooked skin around them, and they are entirely preventable once you know why they happen.

Step by step

Pass it through a sieve.The fastest reliable fix. A fine sieve and the back of a spoon. Nobody will know, and it takes a minute.
Use a stick blender for larger quantities.Thirty seconds and the lumps disappear. It also emulsifies any fat, which gives a glossier gravy.
Understand why they form.Flour hitting hot liquid cooks on the outside instantly, sealing dry flour inside. The lump then survives whatever you do to it.
Make a roux next time.Cook the flour in the fat first, for a minute or two, then add liquid gradually while whisking. Each addition is fully incorporated before the next.
Or use a cold slurry.Flour or cornflour mixed smooth with cold liquid, then whisked into the hot gravy. Cold liquid keeps the flour dispersed until it is evenly distributed.
Add the liquid gradually.Especially the first additions. A thick smooth paste that is then thinned is far more reliable than pouring everything in at once.
Whisk rather than stir.A whisk breaks up flour far more effectively than a spoon, and it is the difference between smooth and lumpy in a roux.
Simmer it properly.Flour-thickened gravy needs a few minutes of simmering to lose its raw taste and reach full thickening power.

Tips

A sieve or a stick blender fixes lumps in under a minute. Nobody will know.
Cook the flour in fat first, or mix it with cold liquid. Those are the only two reliable routes.
Whisk, do not stir. It makes a substantial difference in a roux.

Common mistakes

Adding flour straight into hot liquid — The outside of each clump cooks instantly and seals dry flour inside, forming lumps that cannot then be whisked out.
Adding all the liquid to the roux at once — It is far harder to keep smooth. Adding a little at a time, fully incorporating each addition, gives a reliably smooth result.

If it doesn't work

Lumpy gravy

Cause: Flour not dispersed — Fix: Sieve it, or use a stick blender for thirty seconds.

Gravy too thin

Cause: Not enough thickener or not simmered — Fix: Add a cornflour slurry and simmer for a few minutes.

Gravy tastes floury

Cause: Not cooked long enough — Fix: Simmer for several more minutes to cook out the raw flour.

Greasy gravy

Cause: Fat not emulsified or too much of it — Fix: Skim the excess, then blend to emulsify the rest.

Pale and weak flavoured

Cause: Roux not browned, no pan juices — Fix: Cook the roux to a deeper colour and deglaze the roasting tin into it.

Questions people ask

Should I use flour or cornflour?

Flour gives a more traditional opaque gravy and needs longer cooking. Cornflour thickens with less cooking and gives a glossier, clearer result. Both work.

How do I prevent lumps entirely?

Either cook the flour in fat as a roux and add liquid gradually, or mix the thickener smooth with cold liquid before adding it. Both keep the flour dispersed.