Another group of inks are those that change when they make contact with water. These are called hydrochromic inks. A possible application of this type of ink is a gardeners moisture tester. Some plants only grow properly if the soil they are in has the correct water content.

A plastic moisture tester is pushed into the soil alongside the plant. If the water content of the soil is at the right level, the colour of the moisture tested should remain blue. However, if the soil loses too much water then the colour changes to yellow. If too much water is added to the soil then the colour changes to red.
This colour indication helps the gardener keep the water content of the soil at the right level and helps the plant grow to its full potential.

QUESTION:
1. Describe another practical application of a moisture tester that incorporates hydrochromic inks.

CLICK HERE FOR DRAWING AND SHADING TECHNIQUES INDEX PAGE