What Is Cream of tartar and How Can I Use It?

If cream of tartar has turned up in a recipe or caught your eye at the store, here's what you need to use it with confidence and how to choose it, cook it, store it, what to substitute, and 490 recipes to try it in.

Key Points

An acid salt scraped from wine barrels that makes whipped egg whites hold tall, glossy peaks.
⅛ teaspoon per egg white; ½ teaspoon plus ¼ teaspoon baking soda replaces 1 teaspoon baking powder.
A pinch in hot syrup keeps sugar from re-crystallizing into grit.
Lasts years in an airtight jar; check old powder by fizzing it with baking soda and water.

What is cream of tartar?

Cream of tartar is potassium bitartrate, the acid salt that crystallizes on the inside of wine barrels while grapes ferment. Winemakers scrape it out, refiners clean and grind it, and it lands in the spice aisle as a fine white powder with a faint sour bite.

It earns its shelf space for one job above all: whipped egg whites.

Beaten whites are a foam of unwound proteins holding air. A small dose of acid lowers the pH and firms up that protein network, so the foam climbs higher and holds its shape instead of weeping. Add ⅛ teaspoon per egg white once the whites turn foamy, before soft peaks form.

Nearly 500 recipes on Recipeland call for it, from Light Chocolate Angel Food Cake to Rhubarb Mousse.

What It Does in Baking

Foam stability comes first. Meringue, pavlova, soufflé and angel food cake all depend on whites that hold; the acid is what keeps a billowy foam from collapsing into a puddle during the bake.

With baking soda it becomes leavening. Mix ½ teaspoon of cream of tartar with ¼ teaspoon of baking soda and you have the working equivalent of 1 teaspoon of baking powder.

That pairing is the old-school lift behind Dad's Melty Biscuits and classic snickerdoodles, where the leftover tang is part of the flavor.

In sugar work it blocks crystallization. About ¼ teaspoon per cup of sugar in a hot syrup converts a little of the sucrose to invert sugar, and the syrup stays smooth instead of turning grainy. The same chemistry protects marshmallows and fondant.

On its own it is not a leavener. No baking soda, no gas, no rise.

What It Works With

At working doses the powder is nearly flavorless. You are pairing its chemistry, not its taste.

Snickerdoodles are the famous exception, the one place you can actually taste it. That faint tang under the cinnamon sugar is the cookie's signature, which is why swapping in plain baking powder gives you a flatter-tasting cookie.

For meringue I would not reach for lemon juice unless the jar is empty. Juice adds water, water makes a foam slump, and the powder delivers the same acidity dry.

The classic mistake is overdosing. Doubling the dose does not double the stability; past about ½ teaspoon in a six-white meringue, the foam dulls and the finish picks up a sour, faintly metallic edge. Measure level, not heaped.

What to Use Instead

It depends on which job you are replacing.

For whipped whites, use ½ teaspoon of lemon juice or white vinegar per ¼ teaspoon of cream of tartar. Expect a slightly softer foam, and in lemon's case a trace of citrus in a plain meringue.

For leavening, skip the arithmetic and use baking powder. One teaspoon stands in for the ½-plus-¼ pairing above.

For syrups and candy, a squeeze of lemon juice works the same acid trick. Corn syrup solves the problem a different way, adding glucose that gets in the way of crystal growth.

There is no animal product anywhere in the supply chain. It is grape-derived and vegan by default, no label-reading required.

Buying and Storing It

Look in the spice aisle; it is sold in small jars next to the baking spices. A jar usually outlasts its best-by date by years because the compound itself is shelf-stable.

Airtight and dry is the whole game. In a humid kitchen the powder cakes, and light clumps break up with a fork. A jar left open near the stove's steam can set hard enough to need chiseling.

Old jar of unknown vigor? Test it. Stir ¼ teaspoon into warm water with a pinch of baking soda: a vigorous fizz means the acid is still active, a lazy bubble or two means it is time to replace it.