Skip to Content

Why Does Fudge Crystallize?

Why Does Fudge Crystallize?
This post may contain affiliate links. If you click one of these links and make a purchase, I may earn a commission at no additional cost to you. In addition, as an Amazon Associate I earn from qualifying purchases.

Fudge should be a soft, creamy candy with all the sweetness of sugar and the richness of milk and cream. Biting into a gritty piece of fudge full of sugar crystals tells you something went wrong with your fudge. Why does fudge crystallize?

Fudge crystallizes when the dissolved sugar returns to crystal form, creating a grainy texture. Fudge will crystallize if you don’t dissolve the sugar before boiling, splash undissolved sugar on the sides of the pan, stir the fudge mixture while boiling or while hot, or use cold equipment.

Making fudge isn’t tricky, but it can be disappointing when your sugary mixture turns from silky to grainy or your fudge tastes sandy. If you know what causes crystallization, you can prevent your fudge becoming granular and even rescue gritty fudge.

Why Does Fudge Crystallize?

Fudge, like fondant, is a crystalline sweet, meaning that it always contains tiny sugar crystals. These microcrystals make fudge set firmly. However, the texture must be so smooth that you can’t taste or feel the presence of sugar crystals.

So, although you want these crystals to form, you don’t want them to develop too early. If your fudge ends up grainy, it means the fudge has crystallized, and the sugar crystals are large enough to taste.

There are a couple of reasons why fudge crystallizes.

Fudge Crystallizes If the Sugar Doesn’t Dissolve

The primary reason your fudge crystallizes is that the sugar hasn’t dissolved before the mixture starts to boil. Sugar always wants to return to its crystalline state, so it will crystallize if you give it a chance.

Most fudge recipes start by combining sugar, butter, and milk over medium heat. You need to stir continuously until the sugar dissolves and then bring the mixture to a boil.

If you don’t have enough liquid or fat, your sugar won’t dissolve either, so make sure your recipe includes milk, butter, or condensed milk.

Dissolving the sugar first ensures that your fudge will have a velvety texture.

Fudge Crystallizes If There Is Sugar on the Saucepan’s Sides

Another way your fudge crystallizes is if you leave sugar crystals on the side of the saucepan while you bring your mixture to a boil. Splashing the dissolving sugar as you stir is easy.

Unfortunately, the presence of even a few large crystals can cause your fudge to seize and become granular. Sugar crystals encourage more sugar crystals to form.

You can prevent these crystals from remaining on the sides of the pan by doing this:

  • If your recipe includes butter, grease the sides of the pan with a little melted butter before adding the other ingredients.
  • Avoid splashing the sugary mixture by gently swirling the sugar as it dissolves, rather than stirring vigorously.
  • As you stir, wash down the crystals on the sides of the pan with a small pastry brush dipped in hot water. You may need to do this more than once if the mixture is boiling violently.
  • You can also cover the saucepan for a moment to allow the steam to melt the crystals.

Fudge Crystallizes If You Stir It While Boiling

When your sugar has dissolved, and the mixture is boiling, stop stirring. Stirring a hot sugar syrup can cause your fudge to crystallize.

If your recipe contains a lot of milk or cream, you may need to stir occasionally – check what your recipe requires.

Fudge Crystallizes If You Use a Cold Thermometer

Using a sugar thermometer is an excellent way of ensuring that your fudge mixture reaches the correct temperature.

Fudge needs to reach the so-called soft ball stage, where a drop of the mixture will form a limp, sticky ball in water. A more accurate way of telling that your fudge is cooked is when it reaches between 234 and 242⁰F (112 to 116⁰C), as the liquid will then have evaporated.

Unfortunately, plunging a cold thermometer into a hot fudge mixture is a recipe for disaster – the chilly metal can shock the sugar syrup and cause it to crystallize.

Always warm your sugar thermometer before testing the temperature of your fudge.

Fudge Crystallizes If You Beat It While Too Hot

Another critical stage in fudge making is cooling once the mixture has reached the correct temperature. It is essential to beat the mixture to achieve the luscious fudgy texture you’re looking for. However, don’t be tempted to start beating too early.

Take the fudge off the heat and allow it to rest, undisturbed – without any stirring – until it is lukewarm, around 80 to 110⁰F (40 to 55⁰C). You’ll need to wait for about 15 minutes for this to happen.

Stirring the fudge while it is still warm causes seed crystals to form. Seed crystals are the beginning of crystals. A seed crystal could be a tiny dried bit of sugar, a speck of dust, or even an air bubble, any surface that the sucrose or sugar molecules can stick to and form a crystal.

Once you have a seed crystal, it will quickly become a larger crystal as stirring helps the seed crystals and sugar molecules find each other, creating larger crystals and that tell-tale gritty texture.

Allowing your mixture to cool prevents seed crystals from forming too soon.

Once the mixture reaches about 100⁰F, you want crystals to start forming to allow the fudge to set. Beating the fudge at this temperature encourages tiny crystals to develop, making your candy thick and smooth.

How to Rescue Crystallized Fudge

Fortunately, you don’t need to throw out your fudge if it has crystallized. You will probably be able to melt it down again and start cooking from scratch.

Here’s how to fix crystallized fudge:

  1. Put your fudge in a large saucepan with some water (and cream, if your recipe includes it). Depending on how much fudge you’ve made, this could be as much as a cup of water.
  2. Adding a teaspoon of cream of tartar prevents the sugar from crystallizing.
  3. Stir the fudge gently over low heat until the sugar dissolves. Ensure that the sugar has dissolved completely before increasing the heat.
  4. Bring the mixture to a boil, brushing the sides of the saucepan with a pastry brush.
  5. Do not stir the fudge mixture once it is boiling, as this encourages crystallization.
  6. Cook the fudge until it measures the required temperature.
  7. Remove the hot fudge mixture from the heat and allow it to cool to lukewarm – check the temperature with a thermometer – before beating until smooth and thick.
  8. Pour the fudge into a pan to cool and set.

Final Thoughts

Fudge crystallizes if you allow sugar crystals to develop too early in the fudge-making process. Ensure that the sugar has entirely dissolved before bringing the mixture to a boil. Don’t stir the fudge while boiling or while it is too hot.

Once the fudge has cooled to lukewarm, beat it thoroughly to create a silky, luscious texture.