Macarons feets are the identifying mark of the macarons. If it has no feets, we have a meringue cookie, but not a macaron.
Everytime I make macarons, I get excited when the macarons grows feets in the oven.
Sometimes the macarons feets are high and sometimes short, as you can see it in the following pictures:
There are some several factors that affect the size and shape of the feets
Although I've built macarons website, I'm not a macaron professional so I can't say excactly what affects the size and shape of the feets.
From what I've seen, I can say that these factors can affect the shape of the feets:
1. Weather and humidity, especially if the macarons was made with the french meringue method. Macarons batter reacts differentlly according to the humidity. High humidity can cause no macarons feets.
2. The "dryness" of the macaorns before it enters the oven. the macaron should be dry but not too dry.
3. The eggwhites- it should be room temperture. the eggwhites can also affect the macarons feets.
4. The process of folding the whipped egg whites with the icing sugar and ground almond. If we over-fold, the feets will be very short.
5. the baking sheets can also affect, sometimes we can get different result according to the baking sheet, if it's a parchment paper or a silpat..
6.The oven, different results for different ovens.
look at these feets: