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General Questions

  • The glassware I want is not listed on your website. What can I do?

    At DWK Life Sciences we can help design and manufacture customised and bespoke glassware to suit your precise needs. Please see our manufacturing capabilities page for information on our custom project service.

  •  Can DWK Life Sciences manufacture custom glass vials? Can I get DWK Life Sciences products packaged to meet my specific requirements?

    Yes to both questions. DWK Life Sciences’s premium services offering includes custom containers and custom packaging, bar coding, critical cleaning, surface treatment and pre-weighed containers. Please see our manufacturing capabilities page for information on our custom project service.

  • What is the difference between Class AS and Class A accuracy?

    There is no difference in the level of accuracy between class AS and class A. Class AS pipettes and burettes are calibrated to the same exacting tolerance levels as class A products. Class AS pipettes and burettes have a faster delivery time than the class A equivalents due to re-engineered jets. Although the outflow time is quicker with the class AS product, a waiting time must be allowed for the meniscus to settle after dispensing.

  • What are the differences between items that are calibrated ‘To Contain’ and ‘To Deliver’?

    The terms 'To Contain' and 'To Deliver' are ASTM designations which apply to calibrated volumetric glassware. Glassware that is designated ‘To Contain’ (ISO designation "IN") means the indicated liquid volume contained within a vessel. Glassware that has been calibrated ‘To Deliver’ (ISO designation "EX") refers to the indicated liquid volume dispensed from a vessel. All DWK Life Sciences measuring cylinders and volumetric flasks are calibrated "IN". DWK Life Sciences pipettes and burettes are calibrated "EX".

  • What is amber coated glassware used for?

    Amber glass is used in laboratories for the protection of UV sensitive chemicals and materials such as chlorinated chemicals or bio-cultures. Amber glass blocks all UV radiation from 350 to 200nm. The UVC range used for germ killing purposes, between 200 to 280nm is also blocked. But not all UV radiation is blocked by the amber glass.

Properties of glass

  • What is the difference between soda lime glass and borosilicate glass?

    Soda-lime glass and borosilicate glass are the most common types of glass used for laboratory glassware. They have different chemical compositions which determine the physical properties of the glass. Soda-lime glass is less resistant to higher temperatures and chemical corrosion than borosilicate glass. Due to the higher silica and boric oxide content of borosilicate glass, this type of glass has a much lower coefficient of expansion than soda-lime glass, giving it a better resistance to heat and thermal shock. Borosilicate glass also has a superior chemical resistance than soda-lime glass. For more information on the properties of glass please refer to the technical section.

  • What do Class A, Type 1, and Type 3.3 borosilicate glass refer to?

    Type 1, Class A and Type 3.3 are the specifications from different standards that refer to borosilicate glass. Type 3.3 is so named because the coefficient of expansion for borosilicate glass is 3.3x10-6K-1 (20 - 300°C). Pyrex® borosilicate glass meets the specifications of all the following standards. ISO 3585, DIN 12217 - Type 3.3 borosilicate glass. ASTM E-438 - Type 1 Class A borosilicate glass. US Pharmacopeia (USP) - Type 1 borosilicate glass. European Pharmacopeia (EP) - Type 1 glass.

  •  What is the maximum temperature that I can heat Pyrex® and Quickfit® laboratory glass to?

    The maximum recommended working temperature for Pyrex® and Quickfit® glassware is 500°C (for short periods only). However, once the temperature exceeds 150°C extra care should be taken to ensure that heating and cooling is achieved in a slow and uniform manner. Do heat vessels gently and gradually to avoid breakage by thermal shock. Similarly, allow hot glassware to cool gradually and in a location away from cold draughts. If using a hotplate, ensure that the top plate is larger than the base of the vessel to be heated. Also, never put cold glassware onto a hotplate which is already well heated. Warm up gradually from ambient temperature. If using a Bunsen burner, employ a soft flame and use wire gauze with ceramic centre to diffuse the flame. Never apply high temperature or heat sources directly to any item of volumetric glassware as this will impair the volumetric accuracy.

  • What is a ‘hot spot’?

    When heating or cooling glassware always ensure that this is done in a uniform manner. Temperature variances over 100°C across the vessel can cause a 'hot spot', where one area of the glassware item is hotter than the rest of the item. Hot spots can lead to breakages due to the uneven expansion of the glass.

  • How do I prevent Quickfit® joints from seizing?

    Lubricate joints with good quality laboratory grease or alternatively use Azlon® PTFE joint sleeves to avoid any contamination of sensitive reactions by the lubricating grease.

  • What do I do if a plastic component, such as a stopcock or stopper seizes within a glass assembly?

    Place the piece of glassware containing the plastic component (stopcock, stopper, etc.) into an ice bath for approximately 15-20 minutes. The ice bath should contract the plastic component enough to allow the pieces to be separated.

  • Is Pyrex® suitable to use on hotplates?

    Yes, as Pyrex® glassware is made from borosilicate glass it has a maximum working temperature of 500°C (for short periods of time only). Special care should be taken at temperatures above 150°C. Ensure that both heating and cooling are achieved in a slow and uniform manner in order to avoid thermal shock. A heating mantle is the best option for heating a round-bottomed flask.

  • Does sintered glassware have the same properties as Pyrex®?

    Yes. Sintered glassware is made from same borosilicate glass as Pyrex®, therefore, giving the sinters the same chemical and heat resistance properties as Pyrex®. New apparatus with sintered glass discs should be washed before use to remove loose particles of dust etc. Wash the sinter with hot dilute hydrochloric acid followed by a thorough rinse with distilled water. Never subject sintered glassware to differential pressures exceeding 100kN/m2 (15psi). Avoid subjecting sintered glassware to sudden temperature changes or to direct flames. Always heat very gradually. Similarly, cooling should be achieved in a uniform and gentle manner.

  • What is the shelf-life of glass products?

    None of the glass products manufactured by DWK Life Sciences have a shelf life or expiration date as they are not sterile and the material will not degrade when not in use.

  • What does fire-polish mean?

    Fire polishing is a technique employed in glass fabricating. When a glass rod or tube is cut, it leaves a rough, sharp finish. When a flame is applied at the softening temperature of the glass, it melts or "polishes" the rough ends into a smooth glassy finish.

  • How much pressure/vacuum can the glass bottles handle?

    None of the containers we sell are tested for use under positive pressure or a vacuum.

  • Are Wheaton® moulded containers free of heavy metals?

    We meet the CONEG requirement of less than 100 ppm combined total lead, cadmium, mercury and hexavalent chromium.

  • Can I use Pyrex® vessels in a microwave oven?

    Yes, Pyrex® borosilicate glass is completely microwave safe. However, as with any microwave vessel, be sure it contains a microwave absorbing material such as water before placing in the oven. Note also that fittings such as plastic caps may not necessarily be microwaveable.

  • How often should I examine my glassware for damage?

    Before using any piece of glassware, take time to examine it carefully and ensure that it is in good condition. Do not use any glassware which is scratched, chipped or cracked. Defects like these can seriously weaken the glass and make it prone to breakage in use. Try to always ensure that all volumetric glassware is kept meticulously clean and grease free, as dirt and especially grease, can affect the shape of the meniscus and so impair accuracy. Liquids cling to grease which can impair the accuracy and outflow time on pipettes and burettes. Check pipette and burette jets for chips and cracks as they pose a safety hazard and can affect delivery times which may impede accuracy.

  • How do I get the maximum life and performance from my Glassware?

    To obtain the maximum life and performance from glassware, the correct handling and cleaning is essential. Always provide adequate support to glassware at the base. Do not lift, carry or suspend glassware by the neck, rim or side arms. The use of hydrofluoric acid, hot concentrated phosphoric acid and very strong alkalis is to be avoided in borosilicate glassware as these chemicals attack and weaken the glassware.

Cleaning and autoclaving glass

  • Can I autoclave my glassware?

    Yes, all DWK Life Sciences glassware is suitable for autoclaving. Care should be taken to remove or ensure any lids and stoppers are loose when using an autoclave. Open any stopcocks or valves, and do not overload the autoclave.

  • What precautions should I take to ensure my glassware will not be damaged when using an autoclave?

    Never overload an autoclave to ensure enough space is left between items to circulate the high pressure steam. Breakages can occur whilst autoclaving if lids and stoppers are not loosened or removed to allow any trapped air to escape during the autoclave cycle. Always open any stopcocks or valves to prevent the build-up of pressure. Chipped, cracked or broken glassware should not be cleaned in an autoclave. We recommend that defective glassware should be replaced to ensure safety.

  • Will autoclaving my volumetric glassware affect the accuracy?

    No. All volumetric glassware, including pipettes, burettes, cylinders and volumetric flasks can be autoclaved without it affecting the volumetric accuracy of the product.

  • What glassware cleaners are recommended by DWK Life Sciences?

    DWK Life Sciences recommends using Lipsol® detergent with our glassware. Occasionally, stronger acid washes are necessary for certain types of precipitates or residues. It is best to keep these very dilute and be used in an area where there is good ventilation. Make sure you contain the residual acid and dissolved material for proper disposal. This method should only be used when absolutely necessary. The disposal of seriously stained glass maybe a less troublesome and less expensive course of action than using strong acid washes.

  • Why do I need to rinse my glassware after a cleaning procedure?

    Rinsing glassware is important after any cleaning procedure to remove any leftover residue from improper draining, and to remove water marks. Glassware should always have a water rinse after any cleaning procedure followed by a thorough rinse with de-ionised water.

  • How do I remove stains from my glassware?

    To remove stubborn stains soak in a solution of 3% sulphuric acid and 3% hydrogen peroxide. To remove iron stains use a solution containing one part hydrochloric acid and one part water. Caution: Make sure you refer to MSDS sheets for the cleaning solutions and the materials that were in the glassware. Ensure that there will not be any adverse reactions from the combination of the materials.

  • Can I use Ultrasonic Cleaners to clean my glassware?

    Ultrasonic cleaning is a good method of cleaning glassware thoroughly. Ultrasonic cleaners that use heaters are the best. Generally, using an ultrasonic cleaner with a mild detergent will clean most residues from the glassware.

  • How do I clean glassware that has been used in cell culture and microbiology?

    Bacterial contaminated glassware used in cell and microbiology should be soaked in a disinfectant solution and then steam autoclaved followed by a suitable washing and rinsing. Caution: Make sure you refer to MSDS sheets for the cleaning solutions and the materials that were in the glassware. Insure that there will not be any adverse reactions from the combination of the materials.

Glass product questions

  • Can Erlenmeyer flasks be used under vacuum?

    No, flat bottomed vessels should never be used under vacuum. The only exceptions are those products designed specifically for that purpose, e.g. Buchner filter flasks and Quickfit¨ "heavy wall" Erlenmeyer flasks (Product code FEH). Although Pyrex® "Heavy Duty" Erlenmeyer flasks have heavier walls than standard Pyrex® Erlenmeyer flasks, they are not designed to be used under vacuum.

  • Are the keys of Pyrex® stopcocks interchangeable?

    Yes, all Pyrex® brand general purpose stopcocks have fully interchangeable keys. However, please note that a glass key will not fit a barrel designed to take a PTFE key or vice versa. Pyrex® high vacuum stopcocks are not interchangeable and are individually numbered to ensure that the key can always be matched with the correct barrel.

  • What porosities are found in sintered glassware?

    Sintered glass discs are graded from 0 – 5 depending on their respective porosity. Grade 5: with pore sizes from 1.0µm - 1.6 µm (microns). Grade 4: with pore sizes from 10 µm - 16 µm (microns). Grade 3: with pore sizes from 16 µm - 40 µm (microns). Grade 2: with pore sizes from 40 µm - 100 µm (microns). Grade 1: with pore sizes from 100 µm - 160 µm (microns). Grade 0: with pore sizes from 160 µm - 250 µm (microns).

  • What bore size tubing is needed to connect to screwthread connectors?

    All screwthread connectors fit 13mm screwthreads and allow 9mm bore rubber hose and flexible tubing to be attached.

  • What temperature do I need to seal an ampule?

    Our ampules are manufactured from 3.3 expansion borosilicate glass and require temperatures of 820°C in order to seal them.

  • Can I store sealed ampules directly in the liquid phase of liquid nitrogen?

    We do not recommend storage directly in contact with the liquid phase, only the gas phase.

  • Will the Wheaton® Celstir® Spinner Flasks work with other manufacturer's magnetic stirrers?

    Yes. The Celstir® Spinner Flasks will work with other manufacturer’s magnetic stirrer equipment.

  • How can I attach a pipe through the sidearm of a Wheaton® Celstir® Spinner Flask to add/remove media?

    Silicone stoppers that fit the Celstir® Spinner Flasks with 45mm side-arms are available with 0, 1, 2 and 3 holes (¼” diameter). Also available are open-top caps to secure the stopper to the sidearm.

  • What type of fuel should be used in an alcohol burner?

    There are 3 fuels generally used; 90% ethanol, 50% isopropanol or 100% methanol.

  • What size tubing do I need for the Wheaton® Reagent Sprayers?

    Any flexible tubing with an ID of 5-6 mm will work with the Reagent Sprayers.

  • What size cables do I need for the Stainless Steel Bomb Sampler?

    The eye bolt opening is 18.4mm in diameter and the opening in the plunger rod is 4mm in diameter.

  • Can I use the E-Z Sampler with any bottle?

    The bottle must have a 33-400 or 33-430 GPI thread finish.

  • Why are some of the glass Wheaton® Coliwasas samplers prescored?/h3>

    In some instances it may be OK to snap the sampler in half after use and leave in the sampling container.

  • What are the smallest and largest diameter bottles that can be used with the bottle clamps supplied with the Grab Sampler I?

    The smallest diameter bottle would be 64mm and the largest diameter bottle would be 114mm.

  • Can the Wheaton® BOD Aerator 227700 be used with the 60mL BOD bottles?

    No. It only fits the 300mL BOD bottle. Any type of sparger will work. The top of the bottle does not have to be sealed. The smaller the bubble size, the greater the air dispersion.

  • What is the maximum bottle diameter that will fit into the Wheaton® BOD bottle rack W227729?

    The rack was designed for use with Wheaton® 60mL BOD bottles, but will work with bottles up to 48mm in diameter and 125mm in height.

  • What is the maximum bottle diameter that will fit into the Wheaton® BOD bottle rack W227731?

    The rack was designed for use with Wheaton® 300mL BOD bottles, but will work with bottles up to 75mm in diameter and 165mm in height.

  • What size vial should I use to lyophilize 5mL of product?

    When freezing product in glass, the container should not be filled more than half full. If you want to lyophilize 5mL of product, you should select a vial that holds at least 10mL.

  • Why does a freeze dry stopper have a groove near the base whilst an injection stopper does not?

    During freeze drying moisture needs to be extracted or released from the bottle, as this is happening the stopper is partially inserted allowing the water vapour to escape via the groove. When freeze drying is complete the stopper is pushed fully home to seal the vial and therefore prevent the ingress of moisture as vacuum is removed and the vial warms up. An injection stopper is used to seal the vial but the top can be pierced by a needle, when the needle is withdrawn the rubber ‘heals’ itself by closing up and re-sealing the vial.

  • What is the difference between moulded and tubular vials?

    Moulded vials are hot formed by injecting a ‘gob’ of molten glass into a mould. This gob is then pre-formed and then blown out with compressed air to fill the mould. When cooled, the mould is opened and the vial or bottle is removed. Tubular vials are converted from long sections of glass tube known as cane. We use machinery to cut this cane into shorter lengths then manipulate the glass into vials or glass dropper pipettes. Moulded vials tend to be heavier and more durable, being intended for multiple uses or long term storage. Tubular vials are generally used for disposable applications, i.e. one use only. Tubular vials are lighter to store and more tolerant of rapid temperature changes.

  • What is different about EPA vials?

    The Environmental Protection Agency (EPA) is responsible for the monitoring of analytical standards used for environmental analysis in the UK, much of this dealing with the testing of water supplies. For this purpose the vials used for this type of analysis must be free of the chemicals and volatiles that samples are being tested for. For this reason the vials are also referred to as Volatile Organic Analysis (VOA). The vials are defined by their size, volume, and degree of cleanliness. DWK Life Sciences can supply Wheaton® EPA vials complying to three levels of cleanliness. Class 100 EPA vials are supplied pre-assembled and shrink wrapped in clean room packaging after initial cleaning (annealing at up to 600°C for 20 minutes). This is sufficient for most users. Class 200 EPA vials are used for identifying trace amounts and are subjected to a controlled washing procedure, they are supplied with certification detailing the washing process. Class 300 EPA vials are supplied with batch certification.

  • What type of stainless steel are Wheaton® slide racks made from?

    The slide racks are manufactured from 304 stainless steel.

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