Now, there are four factors to consider in why your macaron shells are not drying...
- Overmixed the batter
- Humid weather conditions
- Did not use a fan
- Too impatient and put them in the oven while not completely dry (me sometimes)
Now here is a correct consistency of the batter piped into circles. See how they are not too thin yet not too thick? They have a small shadow around the curve of the circle (this is how I check to see if it is overmixed or not).
If they are not getting dull and dry like this, PLEASE DO NOT PUT THEM IN THE OVEN. They will crack and look ugly and won't be macarons anymore. If you touch it and it wiggles around a bit, leave it to dry longer.
I have two tips that will surely help dry out your macarons (provided you didn't overmix):
1. Use a FAN to dry out your macarons. It will speed up the drying process! I would say by the time you're done doing the dishes, and preheating your oven, the macarons will be dry.
2. Add 2tsp corn starch or potato starch to the batter if it is humid in your area. This will add some extra tackiness to your batter and should dry out your macarons if you use it additionally to the fan.
Now if you undermixed your batter and they cracked, it will look like this...
See how it is lumpy and bumpy? You didn't release most of the air in the batter, making large air pockets.
Now if you overmixed your batter and they cracked, it will look like this...
These are more flat and look like chocolate crinkle cookies. You released too much air in the batter, causing the shell to collapse onto itself and crack.
I hope this helped, and now you should be able to tell the difference :)