What Is Cream of Tartar

Cream of tartar is a fine white powder sold in tiny jars, and many cooks buy one for a single recipe and forget it. It is potassium bitartrate, an acidic salt that crystallizes inside wine barrels and is then purified. In baking, that mild acidity does three useful jobs: it strengthens whipped egg whites, it stops sugar syrups from turning grainy, and it reacts with baking soda to make bubbles.

Because it is used in such small amounts, people often wonder whether it matters. In a meringue on a humid day, an angel food cake or a pan of snickerdoodles, it does. This guide explains how it works, how much to use, and what to reach for when the jar is empty, with an honest look at what each substitute changes.

Where it comes from and what it is

As grape juice ferments into wine, tartaric acid combines with potassium and settles out as crystals on the inside of barrels and tanks. Those deposits are collected, cleaned and ground into the powder sold in the spice aisle. It has a faintly sour, slightly metallic taste on its own, but in the amounts used for baking it adds no noticeable flavor except a soft tang in a few recipes.

Chemically it behaves as a weak acid that does not dissolve quickly in cold water. That slow release is one reason it was a key part of early baking powders and is still used in some today.

Stabilizing whipped egg whites

When you whip egg whites, proteins unfold and form a network around air bubbles. A slightly acidic environment helps those proteins bond in a gentler, more flexible way, so the foam is less likely to over-whip, turn dry and grainy, or leak liquid later. A meringue made with cream of tartar holds its shape longer in the bowl and in the oven.

Add it once the whites turn foamy, before they reach soft peaks. The usual dose is about ⅛ teaspoon per large white, so a 12-white angel food cake takes around 1½ teaspoons. Using a lot more does not add strength and can leave a faint sour taste.

• French meringue and meringue cookies: ⅛ teaspoon per white
• Angel food and chiffon cakes: about 1 to 1½ teaspoons for 10 to 12 whites
• Seven-minute frosting and Swiss meringue: a pinch to ¼ teaspoon per batch

Keeping sugar syrups and frostings smooth

Concentrated sugar syrups want to crystallize back into grains. A small amount of acid splits some of the sucrose into glucose and fructose as the syrup heats, and those simpler sugars get in the way of crystals forming. That is why some fudge, fondant, candy and boiled icing recipes include a pinch of cream of tartar.

It is a helper, not a complete fix. Stirring a boiling syrup, letting sugar crystals cling to the side of the pan, or beating fudge while it is still very hot can still cause graininess. Wash the pan sides down with a wet pastry brush and follow the recipe's cooling instructions as well.

Snickerdoodles and other leavening uses

Baking soda is an alkali that needs an acid to release carbon dioxide. Most recipes get that acid from buttermilk, yogurt, brown sugar or chocolate. Snickerdoodles use cream of tartar instead, and the combination gives them their soft, slightly cracked top and the gentle tang that sets them apart from a plain sugar cookie.

The same pairing works as a homemade baking powder when you run out: whisk 1 part baking soda with 2 parts cream of tartar and use it right away. Unlike commercial double-acting powder, this mix reacts mostly as soon as it gets wet, so bake the batter promptly.

Substitutes and what each one changes

For egg whites, about ½ teaspoon of fresh lemon juice or white vinegar per white gives similar stability. It adds a little liquid and a whisper of flavor, both minor in a meringue or cake. A copper bowl also stabilizes whites, through a different reaction, though few home kitchens have one.

In snickerdoodles, replace each ½ teaspoon of cream of tartar and ¼ teaspoon of baking soda with 1 teaspoon of baking powder. The cookies will be a bit puffier and lose most of their characteristic tang. For syrups, a squeeze of lemon juice or a spoonful of corn syrup does the same anti-crystal job.

• Egg whites: lemon juice or vinegar, about ½ teaspoon per white
• Snickerdoodles: baking powder in place of the soda and cream of tartar
• Syrups and candy: lemon juice or a little corn syrup

Buying and storing

A small jar lasts a long time. Keep it tightly closed in a dry cupboard. It does not spoil, but if moisture gets in it can cake into a hard lump; break it up and it is still usable. If your baked goods taste faintly bitter or soapy after using a homemade leavening blend, the balance of soda to acid was off, so measure carefully with level spoons.

Common questions

Can I leave cream of tartar out of a meringue?

Usually, yes. Whites whip without it, but the foam is less forgiving. It may overbeat more easily and weep sooner, especially in humid weather. If you skip it, whip just to firm, glossy peaks and bake or use the meringue promptly.

Is cream of tartar the same as tartaric acid?

No. Tartaric acid is the pure acid and is much sharper. Cream of tartar is its potassium salt, which is milder. Recipes are written for one or the other, so do not swap them spoon for spoon.

Does cream of tartar go bad?

It does not spoil in a normal pantry and keeps indefinitely if it stays dry. Old cream of tartar works as well as new. The baking soda it is paired with is more likely to have lost strength.