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    Home All Cocktails

    Blue Cocktail - Cerulean Sour

    Published: Jul 4, 2021 · Modified: Apr 15, 2024 by Kimberly · This post may contain affiliate links. As an Amazon Associate I earn from qualifying purchases. · 2 Comments

    Jump to Recipe - Print Recipe
    Side view of a blue cocktail in a coupe glass. Text at the top says "Cerulean sour blue gin cocktail".

    This is the blue cocktail of my dreams! It's a fairly simple gin sour, but with a gorgeous blue hue and an indigo gin layer on top. The blue color comes from both blue spirulina powder and a butterfly pea flower-infused gin.

    vertical shot of layered blue gin cocktail
    Jump to:
    • Creating the Blue Color
    • Float of Indigo
    • How to Float, and Why It Works
    • Ice or No Ice?
    • Making the drink
    • Other Cocktails You Might Like
    • 📖 Recipe
    • 💬 Comments

    Creating the Blue Color

    When I envisioned this cocktail, I knew I wanted a bright blue color, but I didn't want the orange flavor of Blue Curaçao. I wanted a light, bright citrus flavor.

    Enter blue spirulina powder! (affiliate link) This stuff is really neat. I also used it in these Boozy Firecracker Popsicles for the blue layer. It's made of a type of algae, but doesn't have much of a taste, just a super-vibrant color. A little goes a long way!

    cocktail in a coupe glass on a light gray background with gin bottles and flowers in the background

    Float of Indigo

    When I saw the color that the blue spirulina created in the drink, I wanted to add a little something extra to deepen it up a bit and bring some more visual interest. I decided to float Empress Gin on top. Empress is infused with butterfly pea flowers, which give it a deep indigo color.

    The cool thing about butterfly pea flower infusions is that the color changes to purple/pink when it comes in contact with something acidic. This is the same thing that hydrangea do depending on the pH of the soil they grow in. (Hydrangeas are the flowers in the background of my photos -- although you can't eat them!)

    horizontal photo of blue cocktail in a coupe glass with gin bottles and flowers in the background

    How to Float, and Why It Works

    The science behind the float

    Creating a layered cocktail, where two liquids don't get mixed together, can be a challenge. But, it gets much easier when you understand the science behind it. Basically, it's all about density.

    Sugar is the main key here. Although it's not the only factor, as a rule, liquids with sugar tend to be denser than other types of liquid. The more sugar it has, the thicker the liquid, getting closer to being a syrup.

    When we mix the bottom part of the cocktail all together, it has simple syrup, which makes the whole thing thicker than just gin. That way, you can use the plain gin to make a layer on top.

    How to make it work

    The how-to takes a little practice to master. In the photos below, I am just pouring it straight from the bottle onto a spoon, which softens the stream into the glass. However, I definitely recommend using a jigger and measuring first, then pouring from the jigger. That way you won't get a big old mess like in the photo on the left!

    action shot of spilling gin while trying to pour it into coupe glass, with
    pouring purple gin as a float onto blue cocktail

    I found that you can hold the spoon either way. I personally prefer to hold it with the spoon bowl facing up, but I know a lot of bartenders hold it the other way. You can also hold the spoon where it is either touching the side of the glass or getting close to the side. This might help if you're having trouble getting it to work.

    Ice or No Ice?

    It may be a little weird to put ice into a coupe glass, but I knew it would look great with the blue color! You can serve it however you like. The float will still work, with or without ice. If you don't use ice, I would suggest chilling the glass really well with an ice-and-water slush before straining the drink into it.

    If you aren't making your own clear ice, try to use the ice that they sell in the grocery store. It's inexpensive and you can just store it in your freezer for a fancier look to your cocktails!

    holding dripping clear ice over blue cocktail in a coupe glass
    adding clear ice to cocktail

    Making the drink

    Despite the fancy look, this is a fairly straightforward gin sour. The difference is that we have to mix the blue spirulina powder into the liquid. You can probably just do this in the shaker, but I wanted to make sure it was all dissolved, so I stirred it in with a bar spoon.

    Once the lime juice, blue spirulina powder, simple syrup and clear gin are measured out, shake everything with ice and strain into your serving glass. Double strain (with a regular cocktail strainer plus a fine mesh strainer) if you want to make sure you get out any lime pulp.

    Then, just float the Empress gin on top like explained in this section above.

    gin cocktail in a coupe glass on a light grey background

    If you want to change up the cocktail, try using a vodka or white rum instead of gin as the base spirit. You can even infuse your own clear spirit with butterfly pea flowers (affiliate link) if you want to make the darker float with that same spirit!

    Other Cocktails You Might Like

    • These Boozy Firecracker Popsicles also use blue spirulina for color
    • Try a Blue Gin & Tonic for a refreshing blue drink, this time using Blue Curaçao liqueur
    • The Shamrock Sour cocktail is a bright green color to contrast with the blue!
    overhead shot of blue cocktail

    📖 Recipe

    blue cocktail in a coupe glass with a purple layer on top

    Cerulean Sour

    Kimberly Salem
    This gin sour is incredibly blue! Using blue spirulina and a float of butterfly pea-infused gin, the color takes this fairly simple drink to the next level.
    5 from 1 vote
    Pin Recipe Print Recipe
    Prep Time 15 minutes mins
    Total Time 15 minutes mins
    Course Drinks
    Cuisine American
    Servings 1 drink
    Calories 182 kcal

    Equipment

    • Cocktail shaker
    • Cocktail strainers (optionally two strainers)
    • Long bar spoon
    • Serving glass (I used a large coupe)

    Ingredients

    • 1 oz lime juice freshly squeezed
    • ⅛ teaspoon blue spirulina powder
    • 1 oz clear gin
    • 1 oz simple syrup
    • 2 dashes lemon bitters
    • ½ oz purple gin Empress, or your own butterfly pea-infused spirit

    Instructions
     

    • Mix together the lime juice and blue spirulina powder until the powder is fully dissolved.
    • Add the gin, simple syrup and lemon bitters.
    • If you are using ice, add it to your serving glass. If not, chill your serving glass with a slush of water and ice.
    • Shake the drink mixture with ice, about 15-20 shakes.
    • Strain into your serving glass.
    • Measure the purple gin into a jigger. Slowly pour the gin onto the bar spoon, held over the top of the glass, so that the gin forms a darker layer on the top of the drink.
    • Serve immediately.

    Video

    Nutrition

    Calories: 182kcalCarbohydrates: 23gProtein: 1gFat: 1gPolyunsaturated Fat: 1gSodium: 17mgPotassium: 52mgFiber: 1gSugar: 21gVitamin A: 14IUVitamin C: 9mgCalcium: 8mgIron: 1mg
    Keyword alcohol, blue, cocktail, gin, spirulina
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    Reader Interactions

    Comments

    1. Kevin Smith says

      July 02, 2022 at 5:40 pm

      Loved this. Tried it tonight. How do you get the cocktail so crystal clear? Mine had a white foam that took ages to dissipate after I double strained it. Thanks.

      Reply
      • Kimberly says

        July 02, 2022 at 6:43 pm

        Hi Kevin, so glad you enjoyed it! I didn't do anything special to avoid foaming... what did you use to juice the lemon? Could be the brand of spirulina and how it interacted with the lemon? If you take a piece of lemon peel and squeeze it so the lemon oil goes on the foam it usually helps to reduce it faster. Cheers! -Kim

        Reply
    5 from 1 vote (1 rating without comment)

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