Dull Surfaces On Dishes Washed In A Dishwasher

Appearance

Once the dishwasher has completed the wash cycle the surface of the china, particularly plates, is dull when normally it would be shiny.

Although this is fairly uncommon as a reported dishwasher fault, it can be caused as stated by poor rinsing and in some dishwashers this can be a fault with the dishwasher itself. However our advice is to first take the steps given below to eliminate all other possibilities before attempting any repair or calling a dishwasher engineer to repair your dishwasher.

Usually the result of:

Calcium carbonate (limescale) film due to insufficient softening of the water - this is the most probable cause.
Thin starchy film due to poor cleaning
Thin detergent film due to excessive detergent or poor rinsing

TIP: compare to glasses in the same wash load as they should exhibit the same problem

Cause & Prevention

CAUSE

Limescale film (calcium carbonate) is by far the most likely reason for this problem. Limescale is deposited when the water hardness is too high in the machine and this can be addressed by ensuring that there is salt in the salt container and by using a good quality detergent.

Dull surfaces can also be caused by starchy foods being partially dissolved in the wash water and are then deposited as a thing film on the surface of the dishes.

Another possible cause can be overdosing of detergent or where the detergent is not correctly dissolved followed by poor rinsing, leading to a thin film of detergent residues on dishes.

To test the cause you can use vinegar to remove limescale deposits whilst water alone will not remove this but water will remove detergent residues. To test for starch a drop of iodine will turn blue when dropped onto the residue.

Treatment

Rewash the affected items after eliminating the cause as above and taking preventative measures as shown below.

Prevention

In hard water areas ensure that the salt container has salt and that it is operating. This is still the case when using "all-in-one" dishwasher tablets as salt may still be required dependent on water hardness.

Use a good quality detergent, we recommend Fairy Active Bursts.

Do not overdose on detergent and do not use products intended for commercial dishwasher use.