A Local Universal Indicator Paper

The local universal indicator is made wholly from the red leafed cabbage leaves. Ethanol or warm water is used as a solvent.

3 leaves from a red leafed cabbage are crushed in a motor, on addition of small quantities of ethanol. The resultant extract is then decanted-this will be the local indicator solution.

A strip of filter paper is then inserted into the resultant solution. This strip will serve as the universal indicator paper.

When the strip is put into various solutions, distinct colours are observed, depending on the extent of acidity or basicity of the test solutions.

With the colourations obtained, a pH chart can be designed to be used with our PH paper.

It can serve as an alternative to the simple acid base indicator in the laboratory and apply in case the laboratory has run out of commercial laboratory universal indicator.


Background information

We are interested in this project to come up with a cheaper indicator paper instead of using the normal indicator paper used in the laboratories which are at times difficult to get. An indicator is a substance which gives a definite colour in an acidic or basic solution.

Juice extract from Red leafed cabbage contains a red pigment and can be used as a pH indicator. This realisation pushed us to make a PH paper out of red cabbage juice.

The pH scale is a measure of acidity. You can buy a pH indicator paper from any biological or lab supply company, which can be used to give you an accurate measurement of the acidic or basic quality of substances you want to test. However, you can also make your own pH indicator using red leafed cabbage juice.

Statement of the problem

Can red leafed cabbage leaves be an efficient raw material for a universal indicator paper?


To develop a cheaper universal indicator paper

To construct a pH chart for the universal indicator paper.


If a strip of filter paper is dipped into a solution extract of red leafed cabbage, it can serve as a consistent universal indicator paper.


Consumes less time

Easily made from locally available resources


Gives consistent results.


It requires basic skills for operation

The solvent used might not dissolve all the pigments in red cabbage

Dependent variables

pH of the solutions used depends on the weakness or strength of the acidity or basicity  in them.

The amount of pH indicator solution obtained depends on the quantity of leaves used and the amount of ethanol added.

The intensity of the colour of the solution depends on the amount of ethanol added and the quantity leaves used.

Independent variables

The colours obtained in various solutions


This project can satisfactorily help schools to arrange for their Universal indicators without actually relying on a supplier. All they’ll need is the red leafed cabbage since all other requirements are readily available in schools.

In the kitchen, the indicator paper will greatly help households to know the extent of acidity or basicity of what they consume before they consume them.

Assumptions and precautions

Hot water dissolves all pigments in the red leafed cabbage.

The local indicator paper will remain consistent.


Label all the solutions to avoid confusion and contamination.

Literature Review

Acids are substances which react with metals, yielding hydrogen gas. With respect to protons, they are donors of protons. Their taste is sour.

Bases on the other hand have a bitter taste. Indicators are substances that show different colours in acidic or basic solutions. Universal indicators can be used to show the strength or weakness of acids and bases.

Indicators can be made locally from flower extracts, though results they give are inconsistent as the colours change overtime.

Scientific advancements have been tried to test if certain plants can give extracts that can serve as indicators.



Red leafed cabbage, Filter paper, Ammonia solution, Knife, Vinegar, Heat, Orange juice, Test tubes, Beaker, Distilled water, Dropper

  1. Cut the red leafed cabbage into pieces
  2. Using a motor and a pestle, crush the red leafed cabbage adding small amounts of ethanol as you crush.
  3. Decant the liquid
  4. Soak a filter paper in this liquid. Allow it to dry and cut the dry coloured paper into test Strips
  5. Dip one of the strips in HCl. Repeat the same with various solutions. Repeat the same with various solution.
  6. Construct a pH chart to show the acidity and basicity of the different solutions.

Distinct colours are observed as tabulated below.


Table 1. Showing colours of various solutions in local pH indicator

HCl Red
Sulphuric acid Red
Vinegar Pink
Orange juice Pink
Distilled water Purple
NaCl solution Purple
Wood ash solution Blue
Baking powder Light blue
Soda ash Light green
Ammonia Green
HNO3 Red
NaOH Yellow


Red leafed cabbage juice contains a pigment and can be used as a pH indicator. It is red, pink, in acids, (pH below 7), purple in neutral solutions (pH  7), and ranges from blue, green or yellow in basic solutions (pH above 7). This knowledge pushed us to make a pH paper out of red leafed cabbage juice.From the above data a pH chart can be obtained


HCl 1 Strong acid
Sulphuric acid 1 Strong acid
Vinegar 6 Weak acid
Orange juice 6 Weak acid
Distilled water 7 Neutral
NaCl solution 7 Neutral
Wood ash solution 8 Weak base
Baking powder 9 Weak base
Soda ash 10 Weak base
Ammonia 11 Weak base
Sodium hydroxide 14 Strong base

From 50 cm3 of the red leafed cabbage extract, 60 strips of the indicator paper can be obtained. One cabbage can give 2000 cm3 extract. It’s therefore evident that locally made indicator papers are cheap and more convenient to use

Data analysis and interpretation

Data presentation

From our data on testing the strength and weakness of various laboratory and household solutions, a summary can be depicted on a graph.


HCl acid and H2SO4 are strong acids hence low pH while sodium hydroxide is a strong base hence has a high pH. Water and sodium chloride have an optimum pH of 7, hence neutral.

Conclusion and Recommendation


When using a red leafed cabbage indicator, distinct colours are observed in acidic solutions, basic solutions and neutral solutions, thus the local indicator is a simple acid base indicator that can be used as an alternative to the existing commercial indicators.


Since this is a very safe method of detecting definite colour change in acidic or basic solutions, it is our hope that this project will be taken much seriously and expanded for local use mostly in our neighbouring schools.

Link to emerging issues

With the rising economic issues, some schools might seriously be in need of universal indicators to use in their schools but lack of adequate funds limit them. Being that the local universal indicator paper is made from locally available resources, it can readily serve as a substitute to the existing expensive commercial universal indicators.

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