Name: Walnut Hair Dye
Ingredients: 49 parts Alum; 5 parts Olive oil; 200 parts Green walnut shells; Rectified spirits; Oil of cloves; Salt (optional)

Why it works: Olive and walnut match in chemistry and in kitchens. They rank in the top 6% of all ingredient pairs, and cooks put them together in 2,087 recipes. Both carry 2-undecenal, which smells sweet. The science ↓

Walnut Hair Dye

Ingredients

Directions

Digest the green walnut shells with alum and olive oil in a water bath until all moisture has evaporated.
Express the mixture and add rectified spirits and oil of cloves for fragrance.
Allow the mixture to stand for one to two weeks, agitating occasionally.
Decant the clear solution for use.

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.

Olive + walnuttop 6% of all pairs

Smell alikestrong

Cooked together2,087 recipes

Shared aroma: 2-undecenal (sweet).
Walnut + clovetop 9% of all pairs

Smell alikestrong

Cooked together1,592 recipes

Shared aroma: eucalyptol (eucalyptus, herbal).
Olive + clovetop 10% of all pairs

Smell alikemoderate

Cooked together5,866 recipes

Shared aroma: eucalyptol (eucalyptus, herbal).
Spirit + clovetop 16% of all pairs

Smell alikemoderate

Cooked together152 recipes

Shared aroma: ethyl octanoate (fruity, wine).
Olive + spirittop 19% of all pairs

Smell alikemoderate

Cooked together131 recipes

Shared aroma: isoamyl acetate (banana, fruity).