Rubbing fat into flour

How to tell it is going right

• The fat is cold when it starts and still firm when the rubbing stops, and the bowl has not warmed under the hands.
• Stopped early, while it still looks like coarse crumbs with pieces of fat visible in it, not worked on to a smooth even sand, which means the pieces have gone.
• Nothing is greasy or glossy and nothing has smeared into a paste against the side of the bowl.
• Liquid added last and only enough to bring it together: pressed, it just holds, with no wet patch and nothing sticking to the hand.
• Rested cold before it is rolled or shaped, so the gluten relaxes and the fat firms again after being handled.

Where it goes wrong The fat was too warm, or it was rubbed until the mixture looked uniform. Once the fat has melted into the flour there are no solid pieces left to steam apart in the oven, so the bake is sandy or tough instead of flaky, and nothing done later puts those layers back.