Earlier this week I refrigerated some rendered bacon fat in a small metal prep bowl, for later use. Today, after making bacon again, I went to add more grease and saw a surprising texture on the surface of the congealed fat (click for full 2592x1456 resolution):

solid bacon fat with wrinkly surface

If it's not clear from the picture, the surface is very wrinkly, with the edges significantly raised---it looks like it expanded unevenly as it solidified, but this would seem to indicate the presence of water. Water and fat, of course, don't mix and it looks totally homogeneous.

I've stored bacon fat plenty of times before and it always had a smooth surface after solidifying---schmaltz tends to be a bit less smooth but still a flat surface. When I look at pictures online, such as in this blog post, I also see nothing but smooth, flat fat.

I don't think I did anything different this time. I've used these metal prep bowls and I've used glass bowls. Does the way it solidifies say something about the quality of the bacon, how the fat was rendered or how it was stored?

It has been in there for 3 or 4 days and we haven't had any earthquakes or step-dancing parties.

Here's the same 60 mL prep bowl with more fat from the same package of bacon added this morning, on top of the older fat, after sitting for ~30 minutes in the fridge---no longer wrinkly! This seems to rule out the particular batch of bacon as an influence.

solid bacon fat with smooth surface

  • Was the wrinkly stuff hard to the touch? Fat is usually rock hard in the fridge.
    – Derpy
    Commented May 30, 2015 at 22:33
  • @Chee'sBurgers Yes, it's definitely fat, and has the same consistency as the newer fat on top. I sliced it down the middle and slid one half out of the prep bowl, and the only difference I can see is that the smooth layer is paler in color.
    – Air
    Commented May 30, 2015 at 23:47
  • When you put it in your container was it hot and did you cover it right away and put it in the fridge without letting it get to room temp. Sometimes we forget to let food/fat get to room temp and cover it too quickly and the condensation forms, then drips, hence the wrinkly design. Just a thought
    – user33210
    Commented May 31, 2015 at 0:06
  • @user33210 I didn't cover it at any point. It might have still been warm to the touch when I put it in the fridge, but it didn't go in right away. Same procedure for the second batch, though.
    – Air
    Commented May 31, 2015 at 1:01
  • 3
    I've never done any experiments on it, but I've seen it plenty of times. I suspect that it has to do with the fat shrinking as it cools (outside sets first, then the middle sets later, sucking the fat down the bowl) Notice how the fat in the middle is shrunken in the middle. When you added more fat later, it would come down to temp more quickly (transferring heat to the already cooled fat). I suspect that using a bowl would increase the effect (being thinner at the edge with more surface area, while the middle would take longer to cool)
    – Joe
    Commented Oct 26, 2015 at 12:39

2 Answers 2


Even though you strained your fat while it was hot there is still micro-particles of bacon proteins left in the fat. These particles hold their heat longer than the rest of the fat as its cooling, and rise to the top, and as it solidifies create the texture and slight color change.


Great pan of precious fat you have. To answer your question, fat and meat contain air and water. When the water and air evaporate the fat will move.Those spaces that do not fill in will be wavy.

  • Generally when you render fat, you're boiling off all the water in the process, and air won't remain either. Are you saying the OP didn't do that? Or that more water somehow came out of the fat afterwards?
    – Cascabel
    Commented Jun 3, 2015 at 0:48

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