• 15.02.2023
  • 5 min

Glass corrosion: What you as a foodservice professional need to know

When glasses are washed in a warewasher, they eventually lose their radiant shine and become dull. This means: milky clouding, matt streaks or fine white lines appear on the glass surface. This is glass corrosion. Find out in this article what this actually is, why it is a normal ageing process and what you as a foodservice professional can do about it.

1 What is glass corrosion?

Glass corrosion is visible damage to the glass surface due to chemical and physical influences. In foodservice, it occurs when washing glasses and usually manifests as milky clouding. Glass corrosion is often also referred to as glass illness or glass disease. The process of glass corrosion cannot be reversed. But you can slow down the process and save costs.

2 How can glass corrosion be recognised?

Glass corrosion usually appears as milky clouding, matt streaks or fine vertical lines. These are caused by a roughening of the glass surface. Note: A rainbow-coloured shimmer is often also mentioned as a sign of glass corrosion. However, these are layers of silicate that have formed on the surface of the glass.

Red wine glass with glass corrosion in form of a weak milky cloudiness (cloud corrosion)
a) Glass corrosion in the form of weak cloud corrosion
Red wine glass with glass corrosion in form of a medium milky cloudiness (cloud corrosion)
b) Glass corrosion in the form of medium cloud corrosion
Red wine glass with glass corrosion in form of a strong milky cloudiness (cloud corrosion)
c) Glass corrosion in the form of strong cloud corrosion
Red wine glass with glass corrosion in the form of white scratches, lines and streaks (linear corrosion)
d) Glass corrosion in the form of linear corrosion

3 How does glass corrosion occur?

While the term may suggest it, glass corrosion is not the reaction of glass with oxygen - but a reaction of glass with humidity, water and chemicals. In foodservice, it occurs when washing glasses. The exchange of ions changes the chemical resistance of the glass. The result: Every time a glass is washed, a tiny amount of the glass material is removed from its surface.

On a new glass with a smooth and even surface, this removal is even and visually undetectable. However, if the glass is older and has already been damaged, more glass will be removed in some spots than others. This changes the way light is refracted and the uneven removal becomes visible: as milky clouding (cloud corrosion) or in the form of fine white lines (linear corrosion).

And what about rainbow-coloured shimmering? This is also a consequence of the removal of glass material. This is because the silicate structure of the glass is also dissolved in the process – and the silicates are deposited as layers on the surface of the glass and then shimmer in rainbow colours. This process is called iridescence.

4 What increases glass corrosion?

The two major causes of glass corrosion are pre-damaged glass and the reaction of glass with steam. There are also a number of other factors that contribute to or accelerate glass corrosion. These include inferior glass quality, too high temperatures during washing and unsuitable chemicals. The end of this article tells you what you can do to protect your glasses against glass corrosion.

5 Can glass corrosion be removed?

As already mentioned: no. Glass corrosion cannot be removed and is not reversible. Once the process has started, it cannot be stopped – it can only be slowed down. However, deposited silicate layers, which shimmer in rainbow colours, can be removed.

6 Do vinegar and similar help against glass corrosion?

No, soaking glasses in vinegar essence and adding a raw potato does not help against glass corrosion. Neither does denture cleaning tablets, vitamin C powder or rubbing glasses with lemon juice and then wrapping them in aluminium foil. And adding two lemon halves to the wash cycle doesn’t help either. There are countless home tips on the internet to prevent glass corrosion – not one will help. The only thing that vinegar can do for glasses is remove limescale deposits.

Practical know-how

Question: “Do expensive glasses belong in the warewasher?”

Yes, that is what glass manufacturers recommend: Along with normal glasses, high-quality and expensive glasses should also be washed in a warewasher – even, for example, mouth-blown and very thin-walled wine glasses with fine stems. This is because – assuming correct handling, the right machine settings and a protective glass rack – they will be washed very gently. Even more gently than is possible by hand.

7 6 tips to prevent glass corrosion

A number of different factors contribute to glass corrosion: Each one has either a positive or negative influence. It starts with the quality of the glasses, includes the machine, the water treatment, the chemicals and the rack, and ends with the correct handling before and after the wash cycle. If you follow the following six tips, you will not completely prevent glass corrosion in your glasses, but you will significantly slow it down. And in the long term, this will save costs.

Verres neufs et de haute qualité comme protection contre la corrosion du verre. Utilisez un lave verre professionnel
// TIP 1
When buying glasses, make sure they are dishwasher safe and high quality: high-quality glasses provide better protection against glass corrosion because lead oxide, aluminium oxide or zirconium oxide is added in the manufacturing process.
Un porte-verres spécial avec des verres parfaitement disposés comme protection contre la corrosion du verre
// TIP 2
Use a special glass rack for glasswashing and when putting them in, make sure that the glasses do not touch each other and that they cannot bump into each other: Damage such as scratches and cracks make particularly susceptible to glass corrosion.
Un technicien de service vérifie le dispositif de traitement de l'eau comme protection contre la corrosion du verre
// TIP 3
Have your water treatment system checked the next time the service technician visits: the settings should be adjusted precisely to the regional hardness level of the water as well as the glasses you are using.
Utilisez les programmes speciaux de votre lave vaisselle professionnel
// TIP 4
Always wash your glasses with the intended glasswashing programme. These adjust all the factors such as temperature, wash pressure and wash time specifically to the different types of glass.
Deux bidons contenant des produits lessiviels pour le lavage du verre et un dispositif de dosage à côté d'un lave verres comme protection contre la corrosion du verre
// TIP 5
When washing glasses, always use special glasswashing chemicals and make sure you use an exact dosage of detergent and rinse aid. This ensures that your glasses are washed as gently as possible.
Pour éviter la corrosion du verre, un panier est retiré du lave verres immédiatement après la fin du cycle de lavage
// TIP 6
Remove the rack from the machine as soon as possible after the wash cycle. If the glasses are left in the steam inside the warewasher for a long time, this increases the risk of glass corrosion.
Professionelle Spültechnik von Winterhalter: die Untertischspülmaschine der UC-Serie.

Glasses love Winterhalter!

As well as glass quality and correct handling, the best protection against glass corrosion is washing the glasses as gently as possible. Winterhalter offers a system solution that has a crucial advantage over other machines: variable wash pressure adjustment. There is no gentler way to wash your glasses!

Find out more now!
Les invités sont assis dans un restaurant avec des verres à vin mousseux sur la table devant eux