Use Indigo™ wide range pH 1-14 acid-base test strips when you have a diverse range of materials and/or aren't sure what to expect. Only $11.50/100 strips.
Typical shelf life of 5 years or more if kept sealed even after opening. The 1 strip for all your health concerns.
The wide range strips only measure in pH 1 step increments and are best used when you have absolutely no idea whether your solution is acid or base. You can use these first to determine which of our other acid or base test strips you should use to measure in more precise 0.5 pH steps.
These are ideal for science fair demonstrations if you want to compare the pH of many different foods or drinks. They are also perfect for showing that the pH scale is logarithmic. In other words, you can take a strong acid like HCl or strong base like NaOH & dilute by a factor of 10 which will change the pH by "1".
These pH test strips feature triple pads on each measuring stick. This is to ensure the best contrast & color comparison under different lighting conditions. Depending on the pH you are measuring any two of the pads will change while the 3rd doesn't.
After dipping the strip, compare the 3 colors to find the closest match. With practice and using the same light source every time, you may be able to infer pH changes of less than 1 pH unit.
In addition to this wide range, single pad acid-base test strip, there are also narrow range, triple pad acid-base pH test strips.
Note (1): Changes can be subtle & may appear different under fluorescent, incandescent or sunlight. So, an experiment done at home in the kitchen might look a little different in the school gymnasium during science fair.
Note (2): The number of strips per pack or vial is approximate.