Coat the back of a spoon
A sauce that coats the back of a spoon is thick enough to cling in an even layer and hold a line drawn through it. It is the classic test for custard.
Also called Coats a spoon.
"Coat the back of a spoon" is a test for when a sauce or custard is thick enough. You dip a spoon in, lift it out and look at the back. If the liquid clings in a smooth, even layer and does not run straight off, it is ready. French cooks call this stage nappe. It is used for pouring custard, ice cream bases, pan sauces and glazes.
How to do it
- Dip a wooden or metal spoon into the sauce and lift it out.
- Turn it over and hold it level.
- Run a fingertip across the back of the spoon, through the sauce.
- Look at the line you made.
How to tell it is done
- Ready: the coating is even and opaque, and the line stays clean with sharp edges. The sauce does not flow back into it.
- Not yet: the sauce is thin and see-through, and the line fills in at once. Keep cooking and test again in a minute.
- Too far, for egg custards: the sauce looks grainy or has small lumps. It has started to curdle.
For an egg custard, this stage is reached at about 77 to 82°C (170 to 180°F). A thermometer helps. Do not let a custard without starch go above about 82°C (180°F).
Why it works
As an egg custard heats, the yolk proteins slowly set and thicken the liquid. As a sauce reduces, water evaporates and the sauce gets thicker. Either way, there is a point where the liquid is thick enough to hold on to a surface. The spoon test shows that point without special tools.
Common mistakes
- Testing on the front of the spoon. The curve holds liquid and fools you. Use the back.
- Raising the heat to speed things up. Custard can go from thin to curdled very quickly. Keep it low and stir all the time.
- Testing a sauce right off a high flame. Sauces thicken more as they cool, so a sauce that already looks thick in the pan may be too thick on the plate.
In recipes
"Cook until it coats the back of a spoon" is the usual phrase. For custard, take the pan off the heat as soon as it does, and pour it into a cold bowl to stop the cooking. Strain it if you see any lumps. It also comes up when you temper eggs for a sauce.
Related terms
- NappeNappe is the thickness at which a sauce coats the back of a spoon and holds a clean line when you draw a finger through it. It is the test for custards.
- Temper eggsTempering eggs is slowly whisking hot liquid into beaten eggs so they warm up without scrambling. It is the key step in custards and pastry cream.
- ReduceTo reduce is to simmer or boil a liquid uncovered so water evaporates, leaving a smaller amount that is thicker and more intense in flavor.
- Crème pâtissièreCrème pâtissière is a thick custard of milk, egg yolks, sugar and starch, used to fill eclairs, tarts and doughnuts. Here is how to make it smooth.
- ThermometerA kitchen thermometer checks the heat of meat, oil, sugar and your oven, so food is safe and cooked how you want. Here is which type to use and how.