Over time, some materials change their properties and may cease to be useful. Bread that was soft when fresh may go hard when stale, while fruit that was firm when fresh may go soft when stale. Food that we call stale is often classed as rubbish.
Food may be discarded if it:
- smells bad (haunga)
- feels hard and stale or soft and pulpy
- looks rotten, contaminated or mouldy (pirau)
- tastes peculiar
- sounds mushy or hollow.
Other materials can be classified using our senses. Timber that feels soft may be rotten, rubber bands that feel hard may have lost their elasticity and be discarded and fabric may rip more easily when it has been in the sun too long. These changes in properties can lead people to classify these materials as rubbish and dispose of them.