How to Make PH Indicator

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Introduction: How to Make PH Indicator


"Wow Amazing Colorful, It's Magic!" "No, This is Science!"

Today with this tutorial you can learn easy way to create pH indicator with red cabbage!

This fantastic vegetable has good property for indicate with different colours the type of pH solution, red when the liquid is acid (pH low, like vinegar) and green or blue when alcaline (pH 14, like Sodium hydroxide). This proprerty is due to a pigment inside the juice: the anthocyanins

For make this instructables you need only the red cabbage and a source of heat for extract the juice.

If you prefer The video check it HERE

Step 1: Start!

Grab a chopping board and cut the Cabbage in tiny piece, this help the juice to get out in the next step, after, put all product in a pan

Step 2: Start to Boil

You only add 1 liter of tap water with your red cabbage and place the pan on the source of heat.
When the water start to boil you can see the water becames dark purple, now you can stop the heat and remove the pan from the fire.

Step 3: Filter

Remove all solid part from the liquid and after filter with a strainer.
You can see a very dark purple, but for regular use you need to dilute with the water, this is the neutral indicator. There is different type of cabbage and the color can change of dark or light , for my perfect indicator I have diluted with 1/3 part of concentrate indicator and 2/3 part of tap water and obtained light purple color

Step 4: Test It!

Ok now the best part of tutorial! the test.
For make this you only need different type of product:
Vinegar PH acid
Lemon juice PH acid
Baking Soda PH alcaline
Ammonia PH alcaline

You only test your product with add few drops of the liquid you want to test in the indicator, and you see the color of the indicator change, red if acid and green or blue if alcaline!

Thank You for your attention and follow me here on instructables :D




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Questions & Answers


Definitely going to try it out and find some kids or teachers, to share it with. Thanks Ludvic :-)

Thank you Ludvic,

Sounds like a good project :-)

I have two questions,

1.) What substance do you use as the "concentrate indicator" ?

2.) Could this be used to test other thingsfor grown ups too, like a ph strip does?

I dilute the ph indicator with the water, add water when you see the liquid get more clear.

You can check all things and if you put some paper in this liquid you can create a useful "paper indicator"

Sorry for the english, thank you so much for the comment

So the "ph indicator" is the liquid made from boiling the red cabbage?
And I am to add some water, to make it get more clear?
It would be great to be able to made paper Ph indicators from this.
so many things are acidy and not good for the diet, but alkaline promote better health.
I can test many things this way, like water, perhaps..

Yes, the water need to get more clear the solution, if you don't dilute with water you can't see the different when the indicator mixed with other substance.

Drop a paper in the solution for 24 h and after let it dry.. Cut the paper in little piece and test on a varius chemical, rubbing on a bar of soap and you see a basic element...

This method isn't really accurate, you can buy the strips indicator for cheap but this experiment is really awesome

I'm in sixth grade so I'm learning pH levels and all that stuff. Fun!

me too we will be making it on teusday

I learned this in middle school with the best science class I had. Glad to find a refresher.

Thank You so Much man to correct me! :D