Introduction: How to Make PH Indicator

Picture of 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!

Picture of 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

Picture of 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

Picture of 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!

Picture of 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



PoProbot (author)2016-01-15

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

PoProbot (author)2016-01-15

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?

Ludvic (author)PoProbot2016-01-15

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

PoProbot (author)Ludvic2016-01-15

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..

Ludvic (author)PoProbot2016-01-15

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

DaddysGal22 (author)2015-03-24

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

queenqm (author)DaddysGal222015-05-03

me too we will be making it on teusday

kimberly.forrest.16 (author)2015-04-11

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

TimothyV (author)2015-04-04


Ludvic (author)TimothyV2015-04-05

Thank You so Much man to correct me! :D

tosacj (author)2015-04-04

Very nicely done. I used to teach chemistry and it brings back memories.

electronixTech (author)2015-03-29

Great instructable. I would use distilled water rather than tap water in case there are minerals in the tap water that would affect the solution.

Etripp (author)electronixTech2015-03-31

Just a small semantic point. Here in the UK (the home of science!) it is ALKALINE

not alcaline. Something to do with potassium (K)

Bverysharp (author)2015-03-27

Great! Just what I have been looking for. The grandson is very interested in Chemistry & colour change, so this is ideal. Thanks!!!

Suzanne in Orting (author)2015-03-26

I'm thinking: soak a freshly washed, white t-shirt in the cabbage juice. Spray, sprinkle, splash the other liquids on it as a totally kid-safe tie dye. I just wonder what to use as a mordant.

Or perhaps, put them all in spray bottles to use on paper. Then the mordant wouldn't be needed.

I wonder if you could use cabbage juice in hand made paper, perhaps by boiling it down first. Then your lemon juice etc would be like e reverse invisible ink.

Oh the ideas.....

I LOVE these ideas!! Are you going to try them out? Or do I have to...

Gotta wait for it to stop raining.

Iif you wash it you would expose it to a base, so everything would go a single color,i think.

Detergent would be basic, but I think that most new shirts would have various fabric treatments that would need to be washed out. Perhaps just good, fresh soft water would work.

maxhuey (author)2015-03-26

Lemon is acidic??

nwlaurie (author)maxhuey2015-03-26

Certainly is: ever heard of citric acid? Comes from citrus fruits.

ptkrf (author)2015-03-26

Last image suggests that cabbage changes colour for each pH value... So far as I know it only goes from 1 to 12. Also since it has organic matter in it, is it really OK to use for measuring strong acids and bases?

Aside from that it's great. reminds me of my childhood...

russ_hensel (author)2015-03-20

Very very nice. As a kid I discovered that some flower do similar things. I think I used something in the rhododendron family. Now my chicory weeds seem to do something like the same thing, and hydrangeas are well know by gardeners to change color depending on the ph of the soil. Investigating this would be a good science project.

Hydrangeas will bloom in diffeerent colors depending on the soil ph.

Ludvic (author)russ_hensel2015-03-20

Sure! there are many plants that have various characteristics similar to red cabbage, : D

jmacdonald13 (author)2015-03-26

Great idea, I've often seen the colour change from pickled cabbage when you dilute it with tap water, our tap water is very hard, never thought of extracting the juice from fresh cabbage. Great project for little and big kids. :-)

threeoutside (author)2015-03-24

Very nice! This would be a great, simple science experiment for my 6-year-old granddaughter!

susiefreckleface (author)2015-03-22

very cool ible. thanks.

mmaatkamp (author)2015-03-21

This is so awesome! I never knew! Gotta buy me some cabbage soon :)

About This Instructable




Bio: Hi, My name is Luigi "Ludvic" for the friends, I really like the recycle, the technology and the Chemistry, another of my hobby is Videomaking ... More »
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