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How to read pH test strips?

ph test paper

Written by Jasper Verhoeven | Last update: 28-04-2020

PH test strips, also known as a litmus test, are used to determine the pH value of a liquid, e.g. ph strips for water to spray the crop with. The pH of a liquid indicates whether a liquid is acidic, neutral or alkaline. In some cases, this is important to know, for example when you want to determine whether a disinfectant is still effective. In this article, our specialist provides more information about how to read and use pH test strips. 

How does a pH test strip work?

pH test strip is a strip of litmus paper with which you can measure the pH value of a liquid. The substance in the paper causes the paper to show a different colour at different acidities. The official pH scale is from 0 to 14, where 0 is very acidic and 14 very alkaline. Some pH test strips can measure a pH from 0 to 14, but there are also pH test strips that can measure only acid or only alkaline substances.

How to use pH test strips?

Take into account the following steps when using pH paper strips:
  1. Dip the pH test strip for two seconds in the fluid which you want to measure
  2. Wait for ten seconds.
  3. Because the strip contacts an acidic or alkaline substance, the strip discolours. The more acidic the fabric, the more red the strip becomes, and the more alkaline the fabric, the more blue the strip becomes.
  4. Use the indicator scale with the different colours on the box provided.
  5. Determine how acidic or alkaline the liquid you measured is

In the video below, product specialist Jan Willem Keijzer measures the pH of the disinfectant in a disinfection mat using a pH test strip. 


The difference between pH test strips and a pH meter

The most important difference between a pH test strip and pH meter is the accuracy of the measurment. A pH meter usually contains a computer and generally gives results to a hundredth of an inch. This is not the case with pH indicator strips, these are less accurate. pH test strips are therefore very useful to quickly determine whether a solution is acidic, neutral or alkaline, but are not suitable for accurate measurements. 

Note: if you are color blind, it can be difficult to read a pH test strip correctly.

What do the colors on the pH strips mean?

The different ph strip colors measure the concentration of hydrogen ions in a solution or in soil. The color on the strip determines the acid or alkalinity state of the item being tested. Through the color, you can learn more about the acid or base quality of the solution, depending on the type of pH paper used.
As mentioned earlier, the pH scale runs from 0 to 14, with a color assigned to each number. At the bottom of the scale is red, which represents the most acidic, and a dark blue at the other end represents 14 and alkalinity. In the middle zone, the pH scale becomes neutral.

pH test strip supplies

Questions about pH test strips

Do you have any questions about the litmus test, how to use pH strips, or would you like to get advice? Please contact product specialist Jan Willem Keijzer, or ask your question using the contact form below. We'll respond within 24 hours on working days.

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Hygiënespecialist Jasper Verhoeven About Jasper Verhoeven

Jasper Verhoeven, product specialist disinfection, is the first point of contact for growers when it comes to hygiene. "Customised advice has become increasingly more important, due to the risen demand for hygiene measures in horticulture and the associated challenges. Every time, I see it as a challenge to help a grower to create the ultimate situation at his enterprise."

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