Good washing results

Every cleaning process, whether carried out by machine or by hand, consists of four or five major factors that influence it. The first four are the mechanical force, chemical action (process chemicals), temperature and time. The fifth factor is water, which serves as the substance for transferring the other four factors to the item being washed or the surface to be cleaned and also carries away the dissolved particles of dirt and food.
The factors affecting the cleaning process are often illustrated in a Sinner circle. The circle demonstrates that the individual factors affect each other.
Below, we would like to show you what effect the five factors have on each other during dishwashing in commercial settings:

Mechanical force

Constant pressure and cycling in the dishwasher using the integrated rinsing systems guarantee direct and even wetting of the items being washed with cleaning solution, thereby removing the soiling.

Chemical action (process chemicals)

Depending on the requirements, doses of suitable cleaning agents and rinse aids need to be added constantly for the entire length of the operating cycle.


The heating elements achieve the temperatures required for optimum removal of soiling as well as sanitisation. Temperatures should reach 55 °C to 65 °C in the cleaning solution and 80 °C to 85 °C in the rinse aid solution. For glass washers, temperatures should reach 55 °C to 60 °C in the cleaning solution and 65 °C ± 2 °C in the rinse aid solution.

Contact time

The contact time is the exposure time, during which the cleaning solution wets the items being washed. The chosen contact time should be adequate to ensure soiling is removed from the items being washed.

For single tank dishwashers, that is, dishwashers with one cleaning cycle zone and one fresh water rinse, programmes with contact times of at least 90 sec. are recommended in order to ensure good, sanitary washing results. Single tank dishwashers typically include under-the-counter dishwashers and hood-type dishwashers such as pass-through dishwashers. For multi-tank dishwashers, that is, dishwashers with at least one pre-rinsing pump, one cleaning cycle zone and one fresh water rinse, contact times of at least 2 min. should be chosen to ensure good, sanitary washing results. Typical multi-tank dishwashers include flight type dishwashers and rack conveyor dishwashers.


Water is the substance for transferring the other four factors to the items being washed and carrying the dissolved particles of dirt and food. The properties of the water have a major influence on the overall results of washing. Therefore, special attention must be paid to the water.

Optimal washing results

Since the named factors mutually affect one another, a perfect balance must be found between them. Only then can optimal washing results be achieved.

Other points that need to be taken into account to ensure good cleaning include the following:

  • The items to be washed should be cleaned immediately after being used. The sooner cleaning takes place after use (thus not giving food long enough to become dried on), the better the washing results will be.
  • Good pre-rinsing is absolutely essential.
  • The items to be washed should be presorted before being loaded in the machine.
  • If possible, cutlery should be pre-soaked.
  • The cleaned items must be left to air dry only.
  • Drying by hand should be performed only in exceptional cases and using only disposable towels.


Cleaning agent and rinse aid

Purpose of cleaning agent

The ingredients in the cleaning agent enable the residual food particles to be removed from the items being washed. Dissolved particles of dirt are finely dispersed and suspended in the cleaning solution. This prevents the dissolved particles from being redeposited on the surface of the items being washed. Other components prevent, for example, precipitation of hard water minerals and assist in removing stains from food, coffee and tea.

Alkaline components ensure the swelling and break-down of food particles such as starches, proteins and fats, and they help prevent corrosion.
Other components used to remove food particles are enzymes.
Polyphosphates or substitutes (complexing agents) prevent to a certain extent hard water minerals (lime scale) from precipitating.
Oxidative components of the cleaning agent, such as active chlorine or active oxygen, support removal of stains from coffee, tea or other food colourings.
Special disinfecting ingredients in the cleaning agent further reduce the level of bacteria.

Use the right cleaning agent in the right amount

Depending on the type of soiling and the items to be washed, the right cleaning agent from the GASTRO STAR line of products will ensure clean and sparkling results. Each individual GASTRO STAR cleaning agent was developed especially for its intended use. This allows the individual cleaning ingredients to achieve maximum effectiveness (use our product search). In addition, the formulas used for GASTRO STAR products are highly concentrated, making them extremely efficient and highly economical. This helps avoid inadequate cleaning or overuse of the product thus, saving you money.
Nevertheless, it should be noted that only the proper dosing of the cleaner counteracts the process of corrosion. Dosing too little of the cleaning agent promotes corrosion and build-up of residues, such as starch, protein and lime scale.

Purpose of rinse aids

The purpose of the rinse aid is to reduce water tension and lower the interfacial tension. This achieves optimum wetting of the items being washed during rinsing with fresh water, allowing the water to run off in a film. Using a rinse aid shortens the time it takes for items to dry. If all the conditions inside the dishwasher are ideally matched, then the process will end with spot-free, dry, and sparkling results for the surfaces that have been washed.

Use the right rinse aid in the right amount

No two rinse aids are the same. When choosing a rinse aid, you should look for one that is appropriate for your conditions in your facility in order to prevent excessive dosing, insufficient drying, inadequate cleaning or wear and tear on your tableware, glassware and utensils. Depending on your requirements, you can use either a universal rinse aid (GASTRO STAR K 1), a rinse aid for plastic tableware (GASTRO STAR K 2), a special rinse aid for glassware (GASTRO STAR K 3) or a rinse aid with low foaming properties (GASTRO STAR K 4). For each of our rinse aids, we ensure that the surfactants used are high quality. The result will be sparkling dishes combined with extreme cost-effectiveness.


Correct dosing

Why is exact and steady dosing of cleaning agents and rinse aids important?

Only a consistent and sufficient concentration of the process chemicals (cleaning agent and rinse aid) for the entire washing process guarantees perfect, economical, hygienic and eco-friendly results. Commercial dishwashers come with the option of automatic cleaning agent and rinse aid dosing units.

How is the right concentration determined?

Following initial assessment of the technical conditions on site, water quality, average degree of soiling and dried-on food as well as the type of items to be washed, the service technicians set the required concentrations of cleaning agent and rinse aid on site.

What requirements must the dosing units meet?
  • The have to dose precisely and durably and they must meet the valid safety regulations.
  • Malfunctions should be optically and/or acoustically perceivable.
  • Redosing of dosing containers and/or exchanging the product packages must be simple and easy to use.
  • he instruction of the staff as to the operation of these systems is absolutely necessary.
What must be observed when using a different product (cleaning agent)?

When changing a product dosing systems and reserve containers must be rinsed with fresh water.
The instructions on the safety data sheet must be observed.


Washing glasses

Even though the smooth surface of glass makes it easy to clean and sanitise, it is more susceptible to changes in temperature and damage from mechanical forces. Because glasses are very delicate items to wash, you should follow the recommendations below:

The items to be washed should be cleaned immediately after being used.

The sooner cleaning takes place after use, the better the washing results will be. Dried-on food and drink make successful cleaning more difficult.

Avoid damaging glasses

The main cause of damage to glass is improper loading in the dish and glass racks. If the glasses touch one another, they may suffer increased damage to their surfaces and finishes. Please also make sure you have enough room available to store used and cleaned glasses near the dishwasher. Furthermore, drinking glasses should not be stacked in the cabinet because that can lead to damage, especially on the rims.

Use a dishwasher and cleaning agent designed for glasses

The high temperatures, longer wash cycles and stronger detergents in dishwashers shorten the service life of glasses immensely. Special glass cleaning agents (e.g. GASTRO STAR FR 30 and its matching rinse aid, GASTRO STAR K 3) and glass washers treat glass more gently, thus lengthening their service life.

Wash cycle duration

The wash cycle should not last longer than 150 seconds. The dishwasher must be opened immediately after the wash cycle to allow the steam to escape. Otherwise, the water that condenses on the glasses will place additional stress on their surfaces, impairing their ability to dry on their own.

It also eliminates the need to dry or “polish” them by hand

Manual drying poses a risk to successful cleaning because even fresh drying towels harbour germs and bacteria. The cleaned items must always be left to air dry.

Cloudy glasses as a result of lime scale

Lime scale deposits always occur when the hard water minerals contained in the water remain on the surface of the glasses after they have dried. If the water hardness is relatively low, a properly adjusted (rinse aid) dosing unit will leave your glasses spot-free when dry. However, if the overall salt content of the water is very high, we recommend using a rinse aid with partially or completely deionised water.

Lime scale deposits can be avoided by using a combination of a cleaning agent designed for hard water (e.g. GASTRO STAR FR 45) and an acidic rinse aid (e.g. GASTRO STAR K2).

Glass dulling as a result of glass corrosion

Glass corrosion is irreparable damage to the surface of glass that can occur following frequent washing in a dishwasher. Though certain types of glass, such as simple soda-lime glass, are more susceptible to corrosion, the effects can appear regardless of the quality of the glass. Cloudy glasses and damaged finishes can be prevented or at least delayed by using special glass cleaning agents.

Important: Dosing too little cleaning agent or rinse aid generally does less to aid the resistance of glasses and their finishes than dosing too much. However, excessive dosing will not improve the results. So, you should make sure you are using the right amount.


Water treatment

What is the importance of water in automated dishwashing?

Water is an absolutely essential part of nearly all cleaning processes. It is the basis for automated dishwashing. Water transports the cleaning agent and rinse aid, it enables the items being washed in the dishwasher to be cleaned mechanically, and — in combination with the cleaning agent’s properties — it holds particles of dirt suspended in a cleaning agent solution. This prevents the dissolved particles from being redeposited on the surface of the items being washed. Water also transfers heat to the items being washed, ensuring perfect rinsing and drying results.

Optimal washing results cannot be achieved without the proper water quality. That makes it especially important to adjust the water quality to meet commercial dishwashing requirements.

What substances does water contain?

Water can contain both solid materials and dissolved substances. Examples of solid materials include sand, rust and tiny particles of dirt from the plumbing system, which can damage the dishwasher or even cause parts like the magnetic valves to fail. The installation of a suitable filter system can help protect against that. Dissolved substances include gases, minerals, salts and organic components. Dissolved gases are primarily those contained in the air: nitrogen, oxygen and carbon dioxide. They have no effect on the results of washing.

Do the salts dissolved in the water affect the washing results?

Minerals and salts do have a considerable effect on the quality of the water. If the water contains high levels of minerals and salts, this can cause spots to form on the items washed as well as corrosion and deposits.

Different water qualities are generally categorised according to their overall hardness. The overall hardness of water is represented by its carbonate hardness (also called “temporary hardness”) and its non-carbonate hardness (also referred to as “permanent hardness”).

The carbonate hardness consists of calcium and magnesium ions that are generated by hydrogen carbonates. When water is boiled, they can cause lime to precipitate and create build-up of what is called “boiler scale”. The non-carbonate hardness consists of calcium and magnesium ions that are not generated by hydrogen carbonates. Examples include magnesium chloride. Even when boiled, these minerals remain in solution and do not precipitate.

According to Germany’s Wasch- und Reinigungsmittelgesetz of March 2007 (based on the EU’s Detergents Regulation of 2004), overall water hardness is divided into the following levels:

Soft: less than 1.5 millimoles of calcium carbonate per litre, or less than 8.4° of German hardness (dH)
Medium: between 1.5 and 2.5 millimoles of calcium carbonate per litre, or between 8.4° and 14° of German hardness (dH)
Hard: more than 2.5 millimoles of calcium carbonate per litre, or higher than 14° of German hardness (dH)

What can be done against water hardness?

Cleaning agents contain ingredients that prevent precipitation of minerals that form hard water deposits (e.g. GASTRO STAR FR 45). For overall hardnesses of 0.54 mmol/l (equal to 3° dH), special water treatment should be performed for reasons of cost-effectiveness. However, even water with an overall hardness of less than 0.54 mmol/l (3° dH) does not absolutely guarantee good washing results. Only if the total salt content of the water is low can spot-free cleaning results be achieved.
There are various methods of treating water depending on the water quality. They are divided into softening, partial deionisation and complete deionisation .

Water softening

Softening involves using an ion exchanger to replace the hard water minerals (calcium and magnesium ions) contained in the water with sodium ions. This removes all the minerals that can precipitate as lime scale from the water. To allow the ion exchanger to perform optimally, it occasionally needs to be refilled with water softener salt (sodium chloride). It should be expressly pointed out that simple water softening still involves the possibility of visible mineral residue being left on the washed items. This will generally dissolve in water.


Since softening cannot lower the total amount of salt contained in the water itself, there is no way to avoid performing partial or complete deionisation of water with extreme salt content in order to achieve optimum washing results. Examples of this method include a two-state ion exchange system or a so-called “mixed-bed exchanger”. This removes all the cations and anions from the water. Another suitable method of deionisation is reverse osmosis, during which water is treated using a membrane.

You can find additional information about water quality and appropriate settings for spot-free washing results available for download free of charge from the website of the Arbeitskreis Gewerbliches Geschirrspülen (Working Group for Commercial Dishwashing): Praxishandbuch (Practical Handbook), Chapter 05, “Wasserqualität” (Water Quality):

There you can also find more information on commercial dishwashing with helpful tips and more detailed articles on the following subjects:

  • Organising and planning dishwashing systems
  • Commercial dishwashers
  • Dosing technology
  • Water quality
  • Process chemicals
  • Porcelain
  • Items made of metal
  • Items made of glass
  • Items made of plastic
  • Hygiene
  • Environment and sustainability