How to select the best features for a Laboratory Glassware Washer

If you would like an overview of the information that you should gather and consider prior to evaluating different manufactures and models of a Laboratory Glassware Washers, please see the companion piece How To Select Your Best “Forever Home” Laboratory Glassware Washer.

When it comes to selecting the best laboratory glassware washer, the first step is to define the purpose and thoroughput which was covered in the companion piece How To Select Your Best “Forever Home” Laboratory Glassware Washer. Once you have gone through that exercise, you can contact your expert equipment specialist at ARES Scientific, knowing that you are well prepared for answering all of the questions that he or she will ask in order to help choose the best laboratory glassware washer for you. However, we know there are some of you out there that like to dive deeper – in fact to become a specialist yourself! In this article we will take an in-depth look at the technical information that will be very helpful to understand while you are in the process of selecting your laboratory glassware washer.


Laboratory glassware washers have a wide array of utility connections: there are connections for cold, hot and/or demineralized water. If hot and cold water is used, it may be recommended to have a water softener, depending on the local water quality. Some lab washers have an integrated water softener, whereas others require separate softening equipment.

Additionally, it is important to look at the electrical connections which can vary from lab to lab for this kind of equipment. While a 115V connection might be available in the lab space already, the washers connected to this voltage have much longer cycle times than washers connected to a three phase 208V connection. Labs using more than one washer or labs with a lot of glassware to clean each day should choose the three phase 208V connection for shorter cycle times.

Washers also require a drain. Many local codes require that drain water be sufficiently “quenched” or cooled before it is released to the drain. Facilities should access the local code and inquire with the manufacturer about configuring the washer to meet these requirements.

Door Configuration

Lab washers can have a glass door or a solid door. A glass door allows the user to look inside the chamber while a program is running. While a solid door does not offer this view, it is for sure the less expensive choice. Also, many lab washers have monitoring features to check the spray pressure to ensure the best cleaning performance and also alert when for example a spray arm is blocked and thus the glass door becomes an optional feature, rather than a necessity.

Cycles and Programmability

When evaluating the actual program cycles for cleaning glassware in a lab washer, optimum cleaning performance but also resource efficiency are important. The first step is for a laboratory to determine the required analytical grade, in other words the degree of cleanliness or the residual contamination which is allowed to remain on the glassware. This then dictates what equipment and features are required of the lab washer. Some applications may require a final rinse with demineralized water, some might even require a thermal disinfection.

Every cleaning process is based on the Sinner’s Circle which illustrates the mechanism of action for cleaning and disinfection processes as a circle with four interdependent sectors representing mechanical action, chemicals, temperature and time.

Within the cleaning process, the individual sectors can be adjusted but their total needs to remain the same. To ensure the perfect interplay of the four factors and thus achieve excellent cleaning results combined with the efficient use of resources, it is important that the laboratory glassware washer is equipped with state-of-the-art mechanical components and innovative features which allow for sufficient settings and programming capabilities. An example is the circulation pump, the heart of every glassware washer. A standard circulation pump constantly operates at the same speed no matter how much cleaning power is needed. However, a variable speed pump automatically adjusts to the different program stages and needs, which allows for optimum cleaning results while also reducing water and energy consumption. An overall improved water efficiency when using laboratory glassware washers automatically results in optimized use of cleaning agents which are required in the cleaning process. Since cleaning agents are a recurring cost factor, it is important to look at ways to reduce the consumption to save money throughout the lifetime of the equipment.

Cleaning Agents and Pumps

When choosing a lab washer, the cleaning agents needed for each program cycle have to be selected too. For cleaning glassware in a lab washer, a lab-grade detergent and neutralizer are needed. For some applications like petroleum, an additional chemical like an emulsifier might be needed. The detergent can be in powder or liquid form. Generally, the powder detergent is added to a dosing compartment which is integrated in the door, whereas liquid detergent is pumped in with dosing pumps. Small lab washers often use peristaltic pumps for the dosing of smaller quantities, whereas larger machines often are equipped with bellows pumps or membrane pumps. The advantage of using liquid detergent is predominantly that the required quantity can be dosed automatically depending on the selected program. This avoids manual under- or overdosing. In this case, the lab washer should be equipped with a dosage monitoring system that can be used to control whether the dosage is performed (flow control) or the level of the dose applied (quantity control). In addition, there are also minimum quantity controls that measure the fill level of the canister and emit a signal or warning if the remaining quantity of detergent is too low. In regards to the available space for the lab washer, there needs to be room for at least two 5L or 10L canisters at the side of the washer. This can be in a side cabinet attached to the washer or, in case the washer is integrated into casework, under the sink next to the washer.


Some lab washers are equipped with a dryer, which ensures that the ambient air is taken in, heated up and blown into the wash chamber to dry the glassware from the outside as well as inside. This requires filtration of the room air taken in, which is done with high-efficiency particle air filters called HEPA filter. For convenience or also if space is limited, it is recommended to choose a washer with integrated active hot-air drying to eliminate the need of additional equipment in form of drying ovens or to eliminate additional valuable space needed for letting the glassware dry on shelves. Note: narrow-necked glassware will not dry without the lab washer having a hot-air drying function.


Flexible programming capabilities ensure the right temperature and time settings for any application from cleaning to disinfection or even pasteurization. For example, typical laboratory glassware with medium soiling can be cleaned at a temperature of 75 degrees Celsius with a holding time of 3 minutes. Plastic labware which is not that temperature resistant may need a lower temperature with a longer holding time instead. That shows how these two factors interact with each other. A standard program cycle for critical research applications takes about 30 to 45 minutes. Depending on the application and soiling, a program cycle could be reduced to only 20 minutes.

Baskets and Inserts

Each laboratory glass washer needs baskets and inserts to properly hold the glassware during the cleaning process. These baskets and inserts are selected based on the type and size of the glassware. In the case of wide-necked glassware (e.g. beakers), cleaning with a spray arm is sufficient. In the case of narrow-necked glassware (e.g. round-bottomed flasks, volumetric flasks, pipettes), a basket or load carrier with injector nozzles is required for adequate inside cleaning of the glassware. The taller the glassware is, the longer the injector nozzle should be and the larger the diameter of the glassware, the broader the nozzle should be. This ensures that the optimal water quantity reaches the internal surfaces of the glassware. In addition, it is also important to bear the weight in mind and select a corresponding adapter or injector nozzle for cleaning larger glassware.

When evaluating baskets and inserts it is also important to note if you have existing washers that are using these types of accessories and whether your new machine will have interchangeability of accessories with your existing investments.


Certain applications require validation protocols for the laboratory washer such as IQ/OQ/PQ which are methods for demonstrating that equipment being used or installed will offer a high degree of quality assurance such that production processes will consistently manufacture products that meet quality requirements.[1] When selecting a laboratory washer, one should assess whether these requirements are necessary for the application and regulating agencies and consult with the manufacturer to determine if protocols are available for purchase.


Warranty and Service

As with any complex mechanical equipment, it is always important to review the manufacturer warranty and service network when evaluating your purchase.

Budget and Important Considerations

Last but not least, monetary resources can sometimes be limited for lab equipment and the temptation is to choose a residential dishwasher for a lab. Lab washers need to be compliant with specific regulatory and safety guidelines for lab equipment and are meant to clean laboratory glassware which entails exposure to harsh chemicals that only higher-quality stainless steel can withstand. While a residential dishwasher is a perfect solution to clean kitchen utensils like plates, wine glasses and silverware, it is not suitable to properly clean lab glassware. The contamination and thus cleaning requirements in a lab are completely different than in a kitchen and thus lab glassware washers are much more powerful than residential dishwashers. Moreover, residential dishwashers do not allow for the required programming capabilities and additionally, the baskets and inserts for a kitchen dishwasher cannot properly hold lab glassware and utensils for being cleaned. A good examples are pipettes or narrow-necked volumetric cylinders which need to be cleaned from the inside so injectors on the wash racks need to ensure the water flow within the narrow inside of these items to get properly cleaned. A residential dishwasher is not capable to do this so it should never be considered for a lab room.

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