# Macarons: Hollow when baked on silpats but not on parchment paper



## icklechef90 (Jun 9, 2017)

Hi, I'm experiencing some issues with my macarons in that all those cooked on silpats have a large air pocket/come out hollow. I've tested by making a batch and baking half on parchment paper and half on silpat, both at the same length of time and same temperature and those on parchment were nice and fluffy inside (a bit brown on top but that's another issue!) Does anyone know what could be causing this? Do I maybe need to adjust the baking time? 

I use french meringue method and am baking in a conventional (no fan) oven at 160C for 16 minutes. I know I can use parchment paper and then place a tray on top to shield from the heat and avoid browning but I'd like for it to work on both, especially as they always look more uniform when using a silpat. 

Any help appreciated!


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## chrislehrer (Oct 9, 2008)

@flipflopgirl was just posting about that in the pro pastry area. No answers yet.

Her theory is that the silicone mat acts as an insulator, so that the top of the pastry pulls away from the stuck bottom. I don't think this is right, because the specific heat capacity of the silicone is under 1 J/kg-K, which means it heats very, very fast.

Since are using silpats, which she didn't specify, I can eliminate one of my guesses.

Here's my current working theory.

The silpat is much slipperier than the parchment. As the meringue mass expands on the silpat, it tries to become a big hollow ball, because the air inside expands and so it blows up like a balloon. However, the cooking stiffens the mixture, and eventually it's too stiff to continue expanding. At this point the stuff on the inside, insulated by the outside, is still wet, and continues expanding with the air. Eventually, all the mixture is stiff and there is basically nothing in the center.

On parchment, however, the meringue mixture on the bottom doesn't expand sideways as fast as the rest, because it sticks a bit. This creates an insulated area, where the heat gets in more slowly. You now have a gradient, from hottest at the top to coolest at the bottom. The stiffening occurs along that gradient, so that the center doesn't have the opportunity to fluff out to the exterior walls before it stiffens, held back by the cooler material below.

If this is true, then the answer with cooking on a silpat (other than don't in this case) would be to add friction. Perhaps a sprinkling of flour might, counter-intuitively enough, create the desired result? Or a drop of water, which has a much greater specific heat capacity (>4 J/kg-K)?


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## flipflopgirl (Jun 27, 2012)

Very good @ChrisLehrer !
My second post noted that Silpat feels greasy to me but I followed up with egg white ( meringue) based products are proven to be incompatible with fat.
I think we may be getting somewhere.

mimi


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## flipflopgirl (Jun 27, 2012)

There are a couple of replies on the other thread that deal with the amt of air in the batter .
Unlike a soufflé (that depends on more air to achieve the expected fluffy outcome) mac batter needs to be almost runny (describe by most tutorials as lava like) for the best outcome.

Interesting subject....

mimi


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## kuan (Jun 11, 2001)

I use the cooked meringue method.  In fact, for most things if I can use a cooked meringue I will.   My reasoning is because it is cooked there is no more change in state with the sugar.  Once you make it, it is going to give you consistent results.


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