Name: Acid Drops
Ingredients: 14 lbs sugar, chopped small; ½ oz cream of tartar; 3 pints water; 3 oz tartaric acid; 1 teaspoon essence of lemon

Why it works: Sugar and cream are a kitchen classic. They rank in the top 9% of all ingredient pairs, and cooks put them together in 43,450 recipes. Both carry 2,3-butanedione, which smells butter, sweet. The science ↓

Acid Drops

Ingredients

Directions

The book gives no oven temperature. The 310°F in the steps was added when the recipe was transcribed, as a starting point.

Make the syrup

Combine sugar, cream of tartar, and water in a clean, bright copper pan.
Place the pan on a brisk fire.
Stir occasionally until it boils.
Remove from heat.
Ensure all sugar lumps are dissolved, crushing any remaining lumps.
Return to heat.
Cover the pan.
Let it sit for 10 minutes.
Remove the cover.
Insert a thermometer.
Boil until it reaches 310°F (crack stage).
Immediately lift off the fire.

Finish and shape

Pour onto an oiled slab.
Spread tartaric acid and essence of lemon over the mixture.
Fold in the edges.
Knead like dough to mix thoroughly.
Pass through a machine.
Break up.
Sift in a coarse sieve.
Bottle the drops.

Recipe from a historical cookbook (Internet Archive).

Transcribed from a scanned cookbook and modernised for today's kitchens. Where the book gave no heat or time, or said "a moderate oven", the temperatures and times here may be modern equivalents rather than the book's own figures.

Explore the science

The flavor team

The pairs that carry this dish. Each one is judged two ways: how much their aromas overlap, and how often cooks already put them together.

Sugar + creamtop 9% of all pairs

Smell alikemoderate

Cooked together43,450 recipes

Shared aroma: 2,3-butanedione (butter, sweet).
Sugar + lemontop 18% of all pairs

Smell alikelow

Cooked together53,532 recipes

Shared aroma: 2-nonenal (fatty, green).
Cream + lemontop 30% of all pairs

Smell alikelow

Cooked together15,640 recipes

Shared aroma: acetic acid (sour, vinegar).

Sugar and lemon barely smell alike, yet cooks put them together in 53,532 recipes: they work on texture and structure more than aroma.

Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs

What each ingredient does

Sugar: Forms the sweet, crisp body of the drops as it cooks into a hard candy.
Cream of tartar: Acid that helps prevent sugar from crystallising, keeping the candy smooth.
Tartaric acid: Adds a sharp, sour taste that is spread over the candy and kneaded in.

The step that matters

Immediately lift off the fire at 310°F. Sugar syrup darkens and turns bitter if it keeps cooking past the target temperature, and the stage moves fast. Lifting the pan off the heat right away stops the cooking at the crack stage, so the candy sets hard and clear.