The Ratio in Your Pan Is Not the Ratio in Your Glass

Both approaches to how much liquid a chai boil evaporates work. What differs is what they cost you, and the cost is what this sets out.

Where the liquid goes

Boiling drives water off as steam and leaves everything dissolved or suspended in it sitting in the pan. Milk fat, milk protein, sugar, tannin and spice oil all stay behind and become steadily more concentrated. A pan starting at four hundred millilitres can finish at three hundred and twenty after five minutes of boiling.

That is a twenty per cent reduction, and every millilitre of it came out of the water side of your ratio. The cup you actually drink is therefore always milkier and stronger than the quantities you measured suggest.

Why the shape of the pan matters

Evaporation happens at the surface, so a wide shallow pan loses liquid several times faster than a narrow one. A twenty-centimetre frying pan and a twelve-centimetre milk pan give noticeably different chai from identical ingredients.

This is the leading reason a recipe that worked in one kitchen fails in another with no visible explanation. A lid changes the rate dramatically, because it returns most of the condensing steam straight back to the pan. Chai is nearly always boiled uncovered, which is a decision about concentration whether anyone intends it or not.

Working backwards from the glass

Decide the finished volume first, since two cutting glasses comes to around two hundred and forty millilitres. Then add roughly a fifth on top for what the boil will remove, which puts you near three hundred to start.

Ground fresh, divide that starting volume by your intended ratio rather than dividing the finished volume you want. Once you know your own pan you can measure this once and never think about the arithmetic again. A scratch on the inside of the pan at your usual starting level replaces the measuring jug permanently.

The consequences for spice

Spice compounds concentrate exactly as the milk solids do, so a longer boil intensifies the masala automatically. A blend dosed correctly for a three-minute boil will taste distinctly heavy after a seven-minute one. This is why the same masala behaves differently in a hurried weekday pot and a slow weekend one.

By the second boil, if you routinely boil long, cut the blend by around a fifth rather than deciding the recipe is wrong.

Ginger in particular turns aggressive under extended reduction in a way cardamom does not.

Topping up mid-boil

Adding water partway through resets the concentration but also drops the temperature and stalls extraction. It is a reasonable rescue for a pan that has reduced too far, but it is not a technique worth planning around. Adding milk instead carries the same temperature penalty while avoiding any dilution of the tea itself.

Ground fresh, either way, give the pan a further minute to climb back before you make any judgement about strength. The better answer is almost always a smaller flame from the very beginning.

Milk fat, water hardness and hob power shift the result more than the recipe admits.

Making it repeatable

Use the same pan for chai every time and the evaporation becomes a constant rather than an unknown variable. Keep the flame at a setting you can describe in words rather than one you set by eye each morning.

At the stall, time the boil instead of watching it, because watching consistently produces longer boils than people believe. Record the starting and finishing volumes once and the ratio arithmetic is solved for good. This single adjustment fixes more inconsistent chai than any change of leaf or blend will manage.

Side by side

The takeaway

Measure what comes out of the pan rather than what went into it, and your ratios will finally hold.

Measure it properly once, then never measure it again.