Butter vs shortening
One is four-fifths fat and a sixth water; the other is essentially all fat. Almost every difference between them follows from that.
The short answer
Shortening holds its shape better, spreads less and stays workable across a wider temperature range; butter tastes of something and browns. Neither is better. Which one is right depends on whether the recipe needed the fat to hold a shape or needed it to taste — and a great many bakers use a mixture precisely because those two wants pull in opposite directions.
Where they differ
| Dimension | First | Second |
|---|---|---|
| Water | About a sixth, which becomes steam in the oven and also hydrates flour proteins. | Essentially none. |
| Working temperature range | Narrow. The gap between too cold to cream and too warm to hold a shape is a few degrees. | Wide, and engineered to be so. Far more forgiving in a warm kitchen. |
| Spread in a cookie | More, because it softens sooner in the oven and the dough slackens before the structure sets. | Less, because it stays solid longer. |
| Flavour | Substantial, and often the reason the recipe exists. | Close to none. This is sometimes an advantage. |
| Browning | Browns readily — the milk solids take part in the Maillard reaction. | Contributes nothing of its own. A shortening bake is paler. |
| Cost of substituting by weight | Swapping in butter adds water and flavour and lowers the working range at once. | Swapping in shortening removes water, so the formulation is drier than it was. |
What this conclusion rests on
Why the water content decides most of it
Butter carries water and shortening carries essentially none, so swapping one for the other by weight changes the fat content and the liquid content together. That single difference accounts for the steam contribution, the browning, and much of the difference in spread — and it is why shortening produces shortness where butter produces flakiness.
The source establishes the shortening effect and the plastic-range requirement. It does NOT give a figure for butter’s water content, and BakeHQ quotes none — the claim rests on the difference being large, which is not contested.
RecordedB. S. Ghotra, S. D. Dyal and S. S. Narine, Food Research International
Does shortening make flakier pastry? Usually the opposite
The claim is repeated confidently in both directions, and the mechanism settles it.\n\nFLAKINESS COMES FROM WATER TURNING TO STEAM between layers of dough that the fat kept separate. Butter carries its own water into those layers; shortening carries none. So where a pastry is flaky BECAUSE of steam — puff, rough puff, a properly layered shortcrust — butter has an advantage that shortening cannot match.\n\nWhat shortening does better is SHORTNESS, which is a different texture wearing a similar name. A short pastry is tender and crumbly because the fat interrupted the structure thoroughly; a flaky one is layered because the fat and the steam held sheets apart. Shortening excels at the first and is at a disadvantage in the second.\n\nWhere shortening genuinely wins on layers is in a warm kitchen, because a butter that has melted into the dough produces neither texture. That is a working-conditions advantage rather than a property of the fat, and it is the honest version of the claim.
Related
Compares
The water content recorded on the butter page is the variable the whole comparison turns on.
Named for the effect it has rather than for what it is made of, which is the clue to when it is the right choice.
Fat plasticity and crystal structure
Why shortening is forgiving in a warm kitchen and butter is not: the width of the plastic range, not the quality of the fat.