The Main Reason Your Potatoes Aren't Crisping Up In The Oven
When we roast potatoes, the desired result is a crisp exterior and a pillowy, velvety interior. Ovens offer the quintessential dry heat mechanism that gives roast potatoes their characteristic crispiness. However, dry heat is only one contributing factor. So if your potatoes aren't crisping in the oven, the problem likely lies in how you place them on the baking sheet.
If roasted potatoes lack their crunchy sheen, overcrowding is usually the culprit. Just as overcrowding bacon or mushrooms in a saucepan causes disappointingly mushy results, placing potatoes too close to each other on a baking sheet will prevent them from crisping while they roast.
Ovens are like saunas, blasting potatoes with dry, hot air. As the hot air circulates the potatoes, their water content escapes as vapor, effectively steaming the insides. However, if there's no space for the air to circulate, the water vapor won't evaporate and the potatoes will sweat. An overcrowded pan will turn a sauna into a steam bath; Your potatoes will cook, but they'll be soft, moist, and bland like steamed potatoes.
Even if you're tempted to save dishes by throwing a mound of potatoes onto one baking sheet, parsing them out over two will give them the space they need to crisp up. When you assemble potatoes on a baking sheet, they shouldn't be overlapping or jam-packed. Ensure that there's just a single layer with at least a sliver of space between pieces.
More roasting tips for crisp potatoes
Overcrowding may be the main reason your potatoes aren't crisping up in the oven, but there are plenty of other tips and hacks you can employ to reap the benefits of roasting, starting with choosing the best type of potatoes. Yukon gold or russet potatoes will retain their pillowy interiors, creating a hearty cushion and key textural contrast to crispy edges.
Cutting potatoes into larger chunks will further bolster this textural contrast and prevent the interior from drying out and caving in. No matter what size you want your potato pieces, make sure that you cut them into equal sizes so they'll all cook evenly.
Roast potato recipes call for higher temperatures between 400 and 450 degrees Fahrenheit, but temperatures vary depending on the type of oven you have. For convection ovens, 400 to 425 degrees Fahrenheit is ideal. Regular ovens require 450 degrees Fahrenheit. Placing your baking sheet on the middle oven rack is also key for even crisping.
While a light coating of oil and high heat is enough to create crispy potatoes, a popular method in British cooking is to parboil them in water with a little baking soda before tossing them in oil and roasting them. The water draws out and coats the potatoes in their own starches, which will then create the crunchiest browned exterior.