Moisture and evaporation in a pizza

Short answer

Dough, sauce, cheese and most toppings are mostly water, and the bake has to evaporate a good share of it before the crust can crisp and brown. When more water arrives than the heat and time can remove — or when it is trapped against the base — it soaks into the dough or pools on the surface, which is what a soggy centre is.

The water budget

Think of a pizza as carrying a water budget. Dough is commonly around 55–75% water relative to flour weight. Tomato sauce is mostly water; fresh mozzarella is a high-moisture cheese, and even low-moisture mozzarella still contains a substantial amount. Vegetables such as mushrooms, courgettes, peppers and fresh tomatoes are largely water and release much of it as they heat.

None of this is a problem in itself — some moisture is what keeps the crumb soft and the toppings juicy. The problem is balance: how much water is on the pizza versus how much the oven can remove in the time the bake lasts.

Evaporation costs a lot of heat

Turning water into steam takes a great deal of energy — far more than heating the same water from cold to boiling. While a surface is still wet, much of the incoming heat goes into evaporation, and the surface tends to stay close to 100 °C. Only once it dries can it climb towards browning temperatures.

That is why a heavily topped pizza bakes slower and paler than a sparse one at the same oven setting, and why high-heat ovens cope better with wet ingredients: they can evaporate water fast enough that the surface still dries in a short bake. In a domestic oven the margin is smaller.

Evaporation versus absorption: why centres go soggy

Water from the topping layer has two places to go. It can evaporate upwards, or it can move downwards into the dough. The centre of a pizza is where the second route wins most often: the dough there is usually thinnest and most heavily sauced, the toppings and cheese form a lid that slows evaporation, and the centre can receive slightly less heat than the edges.

Steam trapped under cheese, or between the base and a surface that was not hot enough, condenses back into the dough. The result is a gummy layer just under the sauce and, sometimes, a base that is cooked underneath but wet above. The same physics explains why a crisp base softens if the pizza is left to rest on a solid board or in a closed box: steam from the hot crumb has nowhere to escape.

How heat and time drive moisture off

The practical levers all act on the water budget. Reduce the incoming water (thicker or drained sauce, low-moisture cheese, pre-cooked or salted-and-drained vegetables, less topping overall). Increase the heat that reaches the wet areas (a fully preheated conductive surface, top heat to dry the toppings). Or extend the time in a way that does not burn the base — for example finishing on a lower shelf or par-baking the base for wet styles.

A pizza that is pale and doughy right through, rather than wet only under the sauce, is usually an under-baking problem rather than a water problem — the oven or surface simply did not deliver enough heat for the thickness of dough.

Common misconceptions

“A soggy centre means the dough was too wet.”

Dough hydration plays a part, but most soggy centres come from water in the topping layer and how well the bake removes it. High-hydration doughs can bake perfectly crisp in enough heat.

“Just bake it longer.”

Longer baking removes more water but can burn the base or dry the rim before the centre dries. Reducing incoming water and improving heat delivery usually work better.

What this page cannot tell you

Water contents given are rough typical ranges; actual moisture varies widely by brand, ripeness and recipe. This page explains the mechanism and the levers, not exact quantities for a given pizza, and PizzaHQ has not measured moisture loss in any bake.

Related

Evidence

• On Food and Cooking: The Science and Lore of the Kitchen (revised edition) — Scribner
• Bread baking – A review — Journal of Food Engineering (Elsevier), vol. 86, no. 4, pp. 465–474
• How to make pizza crust crispy (and why yours isn't browning) — King Arthur Baking Company
• The Pizza Lab (column) — Serious Eats