Is Brass Safe to Cook In? The Science Behind Zinc and Copper Leaching

Brass cookware inspires one of the most common and most mishandled questions in traditional cooking: is it safe? The short answer is yes — conditionally. The longer answer requires understanding two variables: what you cook, and whether the vessel is lined.

Brass is an alloy of copper (60–70%) and zinc (30–40%). Both elements are essential nutrients in small quantities. Both become toxic in large quantities. The cooking surface determines which outcome you get — and the determining factor is the acidity of the food placed inside.

The Indian tradition understood this boundary perfectly. Brass was used for dal, rice, ghee-based preparations, and milk. Acidic dishes were cooked in clay or, later, in tinned copper and brass. This was not arbitrary — it was a functional response to observed outcomes across generations of cooking.

When food contacts brass, a surface exchange occurs: hydrogen ions in acidic food displace copper and zinc ions from the alloy lattice, releasing them into the food. The rate of this exchange depends on two factors — acidity (the stronger the acid, the faster the exchange) and contact time (the longer the food sits in the vessel, the more metal transfers).

A 2020 study published in the International Journal of Environmental Research and Public Health measured copper and zinc concentrations in foods cooked in traditional brass vessels. For neutral preparations (dal, rice), the transfer was within WHO guideline values. For acidic preparations (tamarind-based dishes), concentrations exceeded safe single-meal exposure limits.^[1]

Zinc toxicity from a single excessive exposure presents as nausea, vomiting, stomach cramps, and diarrhoea — symptoms that historically gave rise to the belief that certain foods were "incompatible" with brass. They were not incompatible with brass in a metaphysical sense; the chemistry simply made that combination dangerous.

The pH threshold

The practical threshold is pH 5.5. Foods with a pH above this value (neutral to alkaline) are broadly safe in brass at normal cooking temperatures. Foods below pH 5.5 — tomatoes sit at pH 4.0–4.5, tamarind at 2.5–3.5, lemon juice at 2.0–2.5 — are not.

The degchi (straight-sided pot), patila (deep pot), and kadai (wok-shaped vessel) in brass were the foundation of professional Indian cooking for centuries — in royal kitchens, temple bhojanalayas, and domestic hearths alike. The degchi in particular, still in use in North Indian catering today, is almost always brass.

Temple kitchens — prasadam halls — historically cooked entirely in brass and copper because these metals were considered ritually pure (pavitra). The avoidance of acidic preparations in temple cooking is partly Ayurvedic, partly ritual, and wholly consistent with what food science now confirms.

The WHO sets the acceptable daily intake for copper at 0.5–2 mg per day for adults. The tolerable upper intake level is 10 mg/day. For zinc, the recommended daily intake is 8–11 mg; the tolerable upper level is 40 mg/day. Neutral foods cooked in brass for normal durations contribute copper and zinc well within these ranges.

FSSAI Food Safety and Standards (Packaging) Regulations specify maximum permissible migration of heavy metals from cookware. Brass vessels used for non-acidic preparations meet these standards. The regulations also note that vessels used for acidic food preparations should be lined with an approved food-safe coating — which is exactly what traditional kalai (tin lining) provides.

Kalai is a living craft. Kalaiwalas — travelling tinners — have been applying tin coatings to brass and copper cookware across India for centuries. The process involves heating the vessel, applying molten tin (99.9% pure) to the interior surface with a cloth, and allowing it to cool and bond. The resulting coating is food-safe and typically lasts several years with normal use.

Tin begins to degrade at temperatures above 230°C — which is above normal cooking temperatures for all but very high-heat dry roasting. For frying, boiling, simmering, and steaming, tin lining remains intact and effective.

Finding a kalaiwala is easier than it sounds. In most Indian cities, weekly markets (haats) include travelling tinners. Urban areas have established kalai shops — often generational businesses — in older commercial districts. Retinning costs between ₹100–₹400 per vessel depending on size and is worth the investment to extend the life of good brass cookware.