What Causes Hollow Macaron Shells

Dealing with hollow macaron shells? Here are the top reasons why your French macarons are hollow and how to fix them.

The Trouble with Hollow Macarons

Most bakers start to notice the issue of hollow macarons later in their macaron baking journey. When most bakers begin baking this little French treat, most are likely trying to overcome common hurdles like cracked macaron tops and bumpy shells. As a result, most tend to covet smooth non-cracked shells and frilly macaron feet above all else. But as their macarons start looking better - on the outside anyways - they realize there's a hidden issue that lies deep within their macarons - hollow shells.

Do Hollow Macarons Go Away with Maturation?

Severely hollow macarons cannot be fixed with maturation. If most of the body has burst out of the shell and into the feet or sank down to the bottom causing a huge gaping hole, no amount of maturation will really help these types of macarons. Pressing into the back of the shells in order to push the body back up to the top - which some bakers do to deal with hollows - may be a temporary solution. But, ultimately, it's worth fixing hollow macarons since there is something inherently wrong with the baking technique.

A truly non-hollow macaron is not hollow even before filling and maturation as shown in the video above. If it's just a small gap in the macaron shells, these do benefit from filling and maturation, yay! You'll find that they can completely go away after 24 hours of maturation.

Should I Fix Hollow Macarons?

Having said of all that, it's important to remember that hollow macarons are not a problem for most people who eat your macarons unless they're macaron snobs and to which I say, why are you sharing your precious babies with those people anyways 🙂

All kidding aside, although hollow macarons may taste the same as non-hollow ones, severely hollow macarons are more fragile and lack the distinctly chewy texture of a full and fluffy macaron. Those are two of the reasons why you might want to work on your hollow macarons. But if you're obsessed with non-hollows for the glory, save yourself the frustration. It's important to remember that no matter what they look like, macarons are for eating!

For those who are keen on fixing this problem. Below are some key issues to look out for.

How Do I Fix Hollow Macarons?

Hollow macarons can be fixed by whipping the meringue to the correct stiffness, folding the batter to the ideal consistency during the macaronage stage, rapping the tray after piping, using the correct tools, baking at the optimal temperature and possibly the addition of a "secret" ingredient.

Meringue Stiffness

Over-beating the meringue can cause macaron shells to deflate while baking, resulting in a hollow shell. A good stiff meringue is required for my best recipe, however, over-beating the meringue can have an adverse effect and lead to hollow macarons. This is especially true if your macaron looks almost perfect in every way except for a little gap inside the shell.

If your macarons are looking fabulous in every way already (dainty feet, smooth tops), then this fix is for you. Beat the meringue up to the stiff peaks stage and stop immediately once it has been reached. If you are worried about overwhipping, you can skip the mixer and whip the meringue by hand. Yes! It can be done, check out How to Make Macarons without a Mixer and fancy tools.

How Stiff is Stiff Peak?

Beat the meringue until a small peak points upwards when you pull the whisk out of the meringue. The peak can be small! If you beat until a big clump of egg whites can point upwards, you are probably over-beating. This is worth mentioning as some of you may have been trying to test the peaks with a lot more meringue than is needed.

Another way to scale back on how much you have been beating your meringue is to test the bowl by tipping it upside down. Once the egg whites can cling securely onto the bowl without slipping and you have a SMALL stiff peak, stop beating the meringue.

It's very important to create a stable foundation for your macarons and a lot of it starts with the meringue. The speed at which the meringue is whipped and the temperature of the ingredients also play a role. Take a look at the following post to learn more on how to make meringue for use in macaron baking.

FURTHER READING: HOW TO MAKE PERFECT MERINGUE FOR MACARONS

Folding During Macaronage

The macaron batter should be properly deflated to prevent hollows. If you tend to over-beat the meringue, this will help you counteract that. In the beginning of our macaron baking journey, we were told to be careful with deflating the batter. "It's better to under-fold than over fold,"...etc. But that's where a lot of hollow macaron problems begin - from an under-deflated batter. When you're folding the batter, you don't need to baby it as much as you think. Here is a video on how to fold properly to avoid hollows:

Proper Macaron Batter Consistency

On the flip side, over-folding can also cause hollow macarons and feet that are widely spread apart. When folding during the macaronage stage, constantly test the batter using the Figure-8 test in the video above. The batter should flow steadily without breaking but it should not be too runny either. Aim for a thick honey-like consistency. Here is what to look for in terms of consistency during and after piping:

Rap Tray

Rapping the tray after piping will further eliminate the small gaps in the shells that lead to hollows. Make sure you are tapping it hard enough against a hard surface. In the macaron class I took, the instructor literally dropped the baking trays from waist level down onto the floor. It's quite a violent action and sometimes the shape of the shells do change after rapping. For that, I recommend piping on Silpat mats which are great for retaining the shape of the macaron. Pop any remaining bubbles with a toothpick.

Silpat Mats

Silpat silicone mats are great for retaining the macaron's shape. There are many cheaper silicone mat alternatives out on the market now but I recommend using the Silpat brand. I trust them to have the highest degree of food safety. Also, they are reliable for conducting enough heat to reach the bottom of the macaron shells which helps with reducing hollows. Disclosure: Affiliate Links

Silpat Mats: 11 ⅝ X 16 ½ is the size I use in all the videos showing one single mat on a pan. SILPATS are is the only mat brand I use for baking macarons. This mat has no preprinted templates on it so it's great for using over my free macaron art templates.

Toaster oven sized Silpat mats: are perfect for counter top ovens. I sometimes place two of these on one tray to bake two different sized macarons shells at once. You can easily take out one mat earlier once it's done, leaving the other mat to bake longer. SILPATS is the only mat brand I use for baking macarons.

Bake Time & Temperature

Meringues and by extension, macarons, love heat! Give it as much oven love as you can and you'll see less hollow macarons in your kitchen. You can do this by using a:

a.) higher temperature OR
b.) lower temperature with a longer bake time

325 F for 12-14 minutes is a great place to start. (I know of a baker who likes to go even higher at 350 F for 10 minutes.) I must admit, this is quite a high temperature. Most readers have found that 325 F or higher can cause their shells to become browned so another temperature/time combo I can recommend is 275 F for 18 minutes. You can play with the time/temperature combinations. For every 25 F, compensate with a 2-3 minutes change in the inverse direction.

Some Recommended Baking Temperature and Times for Perfect Macarons:

350 F for 10 minutes - suitable for spacious large ovens
325 F for 12-14 minutes - standard starting point for use with my recipe
300 F for 16-18 minutes
275 F for 18-20 minutes - suitable for smaller ovens with small compartments

FURTHER READING: HOW TO USE YOUR HOME OVEN PROPERLY TO BAKE MACARONS

Silpats VS. Parchment VS. Teflon

Some bakers complain about hollows when using Silpat mats and have given up on them completely even though Silpats produce much better results in terms of retaining the macaron's shape. Sometimes Silpats don't perform as well for fully fluffy shells because of the related issue discussed in the last section: heat. The mats are thicker than parchment paper and don't conduct heat nearly as well.

There are a few adjustments that can be made to compensate for this:

• Use better heat conducting baking pans.
• Put it closer to the heat source if your oven's heating coils are on the bottom.
• Try Teflon paper which better conducts heat.
• Keep a pizza stone underneath the baking tray.
  

Heavy-duty baking pans: This is the cookie sheet I use. It's constructed of aluminized steel, the material of choice for commercial bakeries. It is also heavy duty so it won't buckle while baking . It is also rimless allowing even air flow to the macarons.

Teflon baking sheets: These are great for conducting heat and provides macaron shells the heat that some ovens lack. A great compromise between parchment paper and silicone.

Pizza Stone: A pizza stone in the oven can help stabilize oven temperature for temperamental ovens and provide heat from the bottom.

Convection VS. Non Convection for Macaron Baking

You don't have to get too hung up over whether or not to use the convection setting to bake macarons. I've had both types of ovens and they have both performed equally well for baking macarons. If your batter is at the right consistency, you can bake non-hollow macarons in both a convection or non-convection oven granted that you have found an optimal temperature and bake time. Consistent high temperature is key using the tools provided above. Keep an external oven thermometer to keep track of the temperature in the oven. Keep oven doors closed as much as possible and do a longer pre-heat if needed to reach that consistent temperature. Sometimes it takes a little longer to pre-heat to a consistent heat level.

Magic Ingredient for Non-Hollows?

Although, technically, you should be able to overcome hollow macarons with the right techniques as mentioned above, there is one special ingredient you can consider. There's a lot of buzz around adding egg white powder to the dry ingredients to help combat hollows. I haven't tried it yet but it's something that some bakers have discovered worked for them. If all the above fixes don't work for you, you might want to give it a try.

Please note, egg white powder is NOT the same as meringue powder. Meringue powder contains a mixture of sugar, acids and flavorings while egg white power is just purely egg albumen.

My Secret for Testing Macaron Doneness

If you lower the oven temperature as per above, it's important that you bake for a longer amount of time, otherwise, the meringue will collapse after it cools. How to test the macaron for doneness? I'll cover it in an upcoming post. Stay tuned!

I hope you found this post useful and let me know below if you have any further questions.

XOXO,
Mimi