PUBLISHED : Sunday, 23 November, 2003, 12:00am
UPDATED : Sunday, 23 November, 2003, 12:00am

Why bake cheesecakes and custards in a water bath? The recipes I have read say that it makes them bake more slowly and evenly but why can't I just lower the temperature of the oven?

Baking - which usually takes place from 150 degrees Celsius to 200 degrees Celsius - uses hot, dry heat. The highest temperature water can reach is 100 degrees Celsius, at which point it will boil. Using a water bath (also called a bain-marie) helps to diffuse the heat of the oven so items cook more gently, but - just as importantly - it adds moisture via steam. Most ovens don't have temperature settings that go below 120 degrees Celsius so it is impossible to lower the heat enough so it cooks as gently as in a water bath. Even if oven tem- peratures did go that low, it would still lack the important steam element that lessens the chance of goods drying out.

A water bath is usually used for items containing a high proportion of eggs (as in custards or creme brulee, pictured), which, in order to maintain their creamy consistency, need to be cooked slowly. If they're cooked too quickly, the eggs will curdle, small air holes will appear and the liquid will often separate. The water bath can be used for heavy, dense mixtures (such as cheesecakes) that take a long time to bake. If they are not baked in a water bath, the cheesecake will be overcooked at the edges before the centre has time to set.

A lot of your recipes use metric weights instead of cups, which is the way I learned to cook. Do you have any tips on converting weights to cups, for those of us who don't have a kitchen scale?

Weighing is the most accurate way to measure ingredients and it is much faster once you get used to it. There is also less washing up to do because everything is weighed in one bowl (the one that sits on the scale) instead of having to clean all the different liquid and solid measuring cups used for one recipe.

It's impossible to give one method to convert a weight to wet or dry cup measurements. A cup of sugar weighs 240 grams, while a cup of flour weighs approximately 120 grams. The weight of the flour varies with with type it is (cake, all-purpose or bread) and whether it's measured by sifting straight into the cup, spooning the flour from the canister into the cup, or using the cup to scoop it straight from the canister. A cup of parmesan cheese shaved to a fine powder with a microplane is going to weigh less than a cup of parmesan grated with a standard grater.

The kitchen scale I use cost only $60 and gives both metric and imperial weights. It is a standard 'spring' scale that's appropriate for the home because the increments are small - they're marked at 100 grams and 1 ounce intervals. I test its accuracy by weighing a block of butter - if the scale reads anything but 240 grams, I re-calibrate it by adjusting the small spring under the bowl. I don't use it for leavening ingredients (baking soda, baking powder) or dry, ground spices because it isn't precise enough for such small amounts. Digital scales usually give more precision - some can weigh a single gram.

Most professional bakers use balance scales - ingredients are measured on one side of the scale, while counterweights are put on the other side. These are good for larger quantities but are not that appropriate for the home cook because they take up too much counter space

in the kitchen.